ABO Blood Group

Blood groups are classified depending on the presence of antigen on the blood cells. If a person’s red blood cells express the presence of A antigen, then his blood group is said to be of blood group A and if person’s red blood cells express the presence of B antigen on the surfaces of blood cells then he or she is said to be of blood type B. People with red blood cells which do not express A antigen and B antigen then he or she is said to be of blood type O.

Genetic inheritance will determine the blood group of the child. When a child inherits a pair of A-genes from its parents which has the capacity to express A antigens on red blood cells surface. Such child will have blood group A.

When a child inherits the pair of B genes which is capable of coding the presence of B antigens on the red blood cell’s surface, then such child will have blood group B.

When the child inherits A antigen from father and B antigen from its mother, such child is said to have blood group AB.

When child neither inherits A gene nor B gene, then it won’t be able to express Antigens A and B, which will make them recessive and it belongs to blood group O.

When the child inherits one A or B gene along with one O gene results in either an A or a B, but not to an O blood type.

There are many other rare blood groups such as Bombay Blood Group, INRA, Duffy-negative blood and many other. ABO blood group is incompatible with these rare blood groups.

Blood group is said to be of Rh +ve or Rh -ve depends on the presence or absence of rhesus factor. Presence of rhesus factor makes a blood group Rh +ve and absence of rhesus factor will make blood group as Rh -ve.  The blood transfusion will be carried out depending on the ABO blood group and RH blood group compatibility. We divide blood groups as A+ve, A-ve, B+ve, B-ve, AB+ve, AB-ve, O+ve and O-ve. 

If Father has Blood Group A and Mother has Blood Group B , What will be the blood group of children ??

A1+ve and A2+ve Blood Group

Blood groups are determined by the presence of the type of antigen the surface of the red blood cells. There are many blood antigens present. A – antigen, B – antigen are common.

Some of the other blood antigens that are used in blood typing are C factor, D factor, E factor, S factor, M factor, K factor, Le(a) Factor, Fy(a) Factor, Fy(b) factor and Jk(b) Factor are to name few.

Presence of antigens helps in deciding the blood group of the person. Bombay blood group people will not have A and B antigen, which makes lab technician think that this falls under blood type O. But, Bombay Blood group people will not have even H antigen which is present in O blood type people.

Like that, A blood group people will have the presence of A Antigen. Means, the surface of red blood cells of such person will have A antigen. But, within A antigen there are more than 20 different subtypes.

When a person’s A genes are able to code for expressing A1 subtype antigen then he is said to have A1 blood group. If a person’s A gene is able to code for another subtype antigen called A2 antigen, then he is said to have the A2 blood type. Presence or Absence of Rh factor makes them either Rh+ve or Rh-ve.

So a person who has A1+ve will have the A1 subtype of an A antigen and a person who has A2+ve will have the A2 subtype of an A antigen.

A1 and A2 subtypes are very common among 22+ subtypes of A antigen, other subtypes are very rare. 99% of people will have either A1 or A2. 80% of the people are said to have A1 subtype and it is very common.  

When a person is said to have A1B that means he is able to code for Antigen A with subtype A1 and also antigen B. This makes his blood group as A1B. When a person is said to have A2B that means he is able to code for Antigen A with subtype A2 and also antigen B. This makes his blood group as A2B.

The A1 and A2 subtypes are so similar that they do not need to be distinguished for the purposes of transfusion.

Some of the other A subtypes are different enough to complications when blood is being typed, but these subtypes are so rare that such issues arise very infrequently.

The structure of hemoglobin is subdivided into 4 parts which include 2 α chains (HbA) and 2 β chains (HbB) both genes are located on chromosome 16 and chromosome 11 respectively.

Globally, about 56000 of 332000 births affected with hemoglobin disorders will have one form of thalassemia. It is the most common inherited single-gene disorder in the world with especially high prevalence in countries where malaria is endemic.

Mode of Genetic Inheritance of Thalassemia

Thalassemia is inherited in an autosomal recessive pattern which means the mutated genes that will cause this blood disorder is located on the autosomal chromosomes (11 and 16).

two copies of the same mutated gene has to be present for the disease to develop. It is also a single gene disorder where the mutation will only affect the expression of one specific gene as compared to a complex cluster of genes.

There are two main categories of thalassemia; β – thalassemia and α – thalassemia.

β – thalassemia is caused by point mutations (insertion, deletion or change in a single nucleotide base) that results in defective production of β – globin chains.

Whereas,

α – thalassemia occurs when there are gene deletions in the α – globin gene. The mutations in both types of thalassemia will cause reduced production of its respective globin protein and a relative excess of the other protein.

Without proper functioning globin proteins, there will be more abnormal precursor cells in the bone marrow and will reduce normal red blood cell production. The low production of red blood cells will result in various signs and symptoms of anemia which include dizziness, paleness, dark urine, and jaundice.

Types of Thalassemia

β – thalassemia

β – thalassemia is caused by the deficiency or absence of β – globin, resulting in relative excess of α – globin. Mutations of the β – globin gene are divided into two groups;

β0 mutations where β-globin synthesis is absent, and β+ mutations where β-globin synthesis is delectably lower.

Below is the table illustrating the different mutations on β – globin gene that cause the various sub types of β – thalassemia.

Legend: β (normal gene), β0, β+ (mutated gene)

α – thalassemia

α – thalassemia results from the reduction or absence of α – globin and causes the relative excess of β – globin. There are 4 α – globin genes two on each chromosome 16 and the deletion mutation in one of more of the genes can develop one form of α – thalassemia.

In the table below are the different clinical attributes of the different types of mutations in α – globin genes.

HbH – Haemoglobin H disease which is most common in Asian populations. It usually causes microcytic anemia, jaundice, and splenomegaly.

Hydrops fetalis : A fatal condition for a fetus characterized by pallor, generalized edema, and massive hepatosplenomegaly. If intrauterine blood transfusion is not administered it can cause sever tissue anoxia leading to stillbirth.

With the inheritance pattern of thalassemia genetic tests are available during pregnancy to determine whether your baby has thalassemia and its severity. A sample is taken either by chronic villus sampling from the placenta at the 10th to 12th week of pregnancy or by fetal blood sampling from the umbilical cord around 18 to 10 weeks of pregnancy.

Genetic counseling is also available for anyone planning to have a baby and have family history of thalassemia or suspect that either parent may be carriers.

What type of genetic mutations causes cancer?

Germline mutations are in the reproductive cells (germ cells) in the body, which are the egg and sperm. These mutations will be passed to the next generation thus causing increase predisposition to cancer due to the presence of susceptibility genes.

Somatic mutations are in the somatic cells which could be any other cell in the body not including the germ cells. These mutations are not passed from parent to child and are thus not germline mutations.

Read On Mutations: Why Should You not Marry In Close Relations ? – Mutations !!

What can cause genetic changes that result in cancer?

Majority of cancers are not monogenic which means that it requires a complex array of genes and external factors accumulated to finally cause cancer. Which is why most cancers onset in the later stage of life (40 years old and beyond).

Some environmental factors that can cause genetic changes that result in cancer are carcinogens, exposure to ionizing radiation, and high exposure to the sun’s UV rays.

These environmental exposures can cause DNA mutations by epigenetic modifications that can either silence tumor suppressor genes or enhance growth genes thus resulting in abnormal increase expression of growth genes. This can result in cancer as the cell’s function is not defective and may grow and divide at an abnormal rate.

The build-up of cells can cause a tumor to form and it could increase the release of certain enzymes or hormones in the body above the homeostatic level. If the tumor is benign it can still be surgically removed, however, if a capillary system grows on the tumor it will become metastatic which means cancerous cells of a tumor is able to squeeze through the capillary wall and be transported to infect other parts of the body.

Genes associated with cancers

One of the most common genes associated with human cancers is the TP53 gene. It normally codes for a tumor suppressor protein (p53) that functions as an antiproliferative protein in response to cell stresses.

Somatic mutations of this gene are known to be associated with many cancers, germline mutations of TP53 gene result in a disorder known as Li – Fraumeni syndrome which will cause early – onset of a spectrum of cancers.

BRCA1 and BRCA2 genes are associated with breast and ovarian cancer. These genes are tumor suppressor genes that normally function in regulators for DNA repair, transcription of DNA to mRNA, and also cell cycle response to DNA damage.

Germline mutations of these genes that are inherited in an autosomal recessive manner can predispose the next generation to breast and ovarian cancer. Usually, there is a 50% chance of individual progeny of inheriting the mutation variant if a parent has cancer.

Genetic counseling is also available for parents who are planning to have children and prenatal tests for families with the history of cancers that may be at risk of cancer predisposing genes in the family gene pool.

References

1. Olivier, M., Hollstein, M., & Hainaut, P. (2010). TP53 Mutations in Human Cancers: Origins, Consequences, and Clinical Use. Cold Spring Harbor Perspectives in Biology, 2(1), a001008. http://doi.org/10.1101/cshperspect.a001008
2. Petrucelli N, Daly MB, Pal T. BRCA1- and BRCA2-Associated Hereditary Breast and Ovarian Cancer. 1998 Sep 4 [Updated 2016 Dec 15]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2017. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1247/
3. Yoshida, K. and Miki, Y. (2004), Role of BRCA1 and BRCA2 as regulators of DNA repair, transcription, and cell cycle in response to DNA damage. Cancer Science, 95: 866–871. doi:10.1111/j.1349-7006.2004.tb02195.x

In the United States, 5% of children have ADHD and approximately 11% of children ages 4 to 17 have been diagnosed with ADHD with increasing percentage each year. A systematic review and meta-analysis done by Rae Thomas and colleagues came up with a pooled prevalence estimate of 7.2% of the worlds child population of having ADHD. In another meta-analysis published in January 2017 showed a pooled prevalence of 6.26% of in children and adolescents under 18 years old in China with ADHD. The statistics should be a cause for concern as to what can be done further to alleviate the causes of ADHD incidence.

Causes of ADHD (Genetic and Environmental)

Both genetic and environmental factors play different roles in causing ADHD. Various studies have shown that specific genes and family history contribute to the inheritance of ADHD. Genetic susceptibility of ADHD is linked to multiple genes, some of these genes include; catecholaminergic genes like DRD4 gene that codes for dopamine D4 receptor. In a recent study of an Iranian population, DRD4 gene polymorphisms in exon 3 showed an association between 4R(repetition) alleles of DRD4 and ADHD in children ages 6 to 14.

There are also environmental risk factors to consider when discussing the causes of ADHD. Environmental factors have to be highlighted as they can be prevented or could even help reduce the risk of a child having ADHD. It was found in a research by Alina Rodriguez and Gunilla Bohlin that both maternal smoking and stress during pregnancy are separately related to ADHD symptoms, especially in boys. Another study using the children-of-twins design on a large Australian twin cohort concluded that maternal alcohol use would cause a direct risk to ADHD in their children. Some other environmental risk factors for ADHD are illustrated in the table below.

How do I know if my child has ADHD?

3 main signs of ADHD are inattentiveness, hyperactivity, and impulsiveness. Guidelines used by healthcare professionals are provided by the American Psychiatric Association’s Diagnostic and Statistical Manual (DSM – 5). These guidelines help in the diagnosis of ADHD in children under 16 years old. These criteria include a list of signs and symptoms for each of these categories; inattentiveness, hyperactivity, and impulsiveness. People diagnosed with ADHD would show six or more symptoms in the list are met for children under 16 years or five or more symptoms met for those 17 and older for a period of 6 months. But of course, if you observe any unusual behavior from your child that could be related to ADHD please consult a healthcare professional for advice on the diagnosis.

Care and treatments for ADHD children.

There is no one drug or therapy that can cure ADHD, a holistic approach that includes environmental and pharmaceutical factors could help a child in effectively overcoming ADHD.

Some medications that are used for ADHD treatments are methylphenidate, dexamfetamine, lisdexamfetamine, atomoxetine, and guanfacine. These medications would help to ease any symptoms of ADHD as they are stimulants that temporarily alters the brain chemistry to help control impulsive behavior or hyperactivity. As with any form of pharmaceutical drugs they come with some side effects, common side effects of the medications include nausea, the small increase in blood pressure and heart rate, or headaches. Remember to always consult your doctor on the right dosage for your child so as to prevent any of these adverse side effects.

Therapy for the child should also complement the medications. This would include behavior therapy to manage the child’s behavior towards different situations. Training and educating parents on the care and understanding of their child’s condition is also another important form of treatment. As this would give parents the knowledge of how to foster good behavior in their child and thus provided a less stressful environment at home for the child to heal.

References 

• Faraone, S. V., & Mick, E. (2010). Molecular Genetics of Attention Deficit Hyperactivity Disorder. The Psychiatric Clinics of North America, 33(1), 159–180. http://doi.org/10.1016/j.psc.2009.12.004
• KNOPIK, V., HEATH, A., JACOB, T., SLUTSKE, W., BUCHOLZ, K., MADDEN, P., . . . MARTIN, N. (2006). Maternal alcohol use disorder and offspring ADHD: Disentangling genetic and environmental effects using a children-of-twins design. Psychological Medicine, 36(10), 1461-1471. doi:10.1017/S0033291706007884
• Rodriguez, A. and Bohlin, G. (2005), Are maternal smoking and stress during pregnancy related to ADHD symptoms in children?. Journal of Child Psychology and Psychiatry, 46: 246–254. doi:10.1111/j.1469-7610.2004.00359.x
• Tabatabaei, S. M., Amiri, S., Faghfouri, S., Noorazar, S. G., AbdollahiFakhim, S., & Fakhari, A. (2017). DRD4 Gene Polymorphisms as a Risk Factor for Children with Attention Deficit Hyperactivity Disorder in Iranian Population. International Scholarly Research Notices, 2017, 2494537. http://doi.org/10.1155/2017/2494537
• Thapar, A., Cooper, M., Jefferies, R., & Stergiakouli, E. (2012). What causes attention deficit hyperactivity disorder? Archives of Disease in Childhood, 97(3), 260–265. http://doi.org/10.1136/archdischild-2011-300482

Diagnosis of any genetic disorders that was inherited or has developed during pregnancy can be done through genetic tests during various stages of pregnancy. Earlier detection of genetic disorders such as chromosomal aberrations like trisomy 18, trisomy 21 (Down Syndrome), and birth defects like spina bifida can allow parents to be prepared for the medical costs and how to care for their child.

Types of genetic tests and genetic disorders during pregnancy

Genetic tests are divided into two categories, screening tests, and diagnostic tests. Genetic screening tests are blood tests done usually before pregnancy or in early pregnancy to determine the risk of your baby of inheriting a genetic condition. On the other hand, diagnostic tests are done during pregnancy that can identify and confirm any chromosomal anomalies in your baby.

Genetic screening tests are relatively safe for you and your baby as they only require a blood or saliva sample. Screening tests discussed today will include carrier screening, first-trimester screen, and multiple marker screening.

Carrier Screening Tests

Carrier screening tests are also done for single gene disorders such as cystic fibrosis, thalassemia, sickle cell anemia, and Tay – Sachs disease. This screening test can be used to check if both parents are carriers of a genetic mutation that may cause a possibility of their baby inheriting a genetic disorder.

Being carriers of the disease means that both parents are both heterozygous as they carry one dominant and one recessive allele of the gene. As a carrier, the recessive gene is not expressed therefore would not have the disease. This screening test is more commonly done as early as possible, either before pregnancy or early in the pregnancy.

First-trimester screen

The first-trimester screen involves a combination of an ultrasound of your baby’s nuchal fold (nuchal translucency) and a blood test. The blood test would include screening for genetic disorders such as Down Syndrome (trisomy 21), trisomy 18, and spina bifida (open neural tube defect) and other chromosomal anomalies.

                                           Courtesy: Fetal Medicine Foundation Canada

Multiple marker screening (Triple or Quad screen)

Double marker screening or triple marker screening or quad marker screening test is done during the second trimester of pregnancy to assess the risk of the baby having genetic conditions like Down Syndrome, trisomy 18, and spina bifida. It is done by drawing blood from the mother and subsequently measured for the concentration of different components in the blood.

Measured components are alpha-fetoprotein (AFP), unconjugated estriol (uE3), human chorionic gonadotrophin (hCG), for a triple test. Inhibin A is included for a quad screen test. High levels of alpha-fetoprotein (AFP) could mean that you’re expecting more than one baby or it could be a sign of spina bifida (open neural tube).

However, low levels of alpha-fetoprotein (AFP) and unconjugated estriol, and high human chorionic gonadotrophin (hCG) and inhibin A could mean that your baby has the higher risk of Down Syndrome. As for other chromosomal aberrations such as trisomy 18 where your baby has an extra chromosome 18, low levels of AFP, estriol, and hCG could be associated with higher risk of them.

When a triple or quad screening is done following first – trimester screening tests it is known as integrated or sequential screening.

Genetic counseling may be suggested after any abnormal results arise from genetic screening to discuss any possible birth defects.

Unlike screening tests, genetic diagnostic tests will provide more concrete evidence of your baby having a genetic birth defect or not. These tests are invasive as a needle is inserted in the womb, thus have a small risk of miscarriage. Genetic diagnostic tests to be discussed will be chorionic villus sampling and amniocentesis. These are the only two tests that can diagnose genetic defects during pregnancy.

Chorionic Villus Sampling

Performed during the first trimester (10-12 weeks) of pregnancy, to determine the total chromosome number of the baby especially to check if your baby has the normal number of 46 chromosomes. This diagnostic test is advantageous because it is done earlier in the pregnancy to determine any chromosomal defects such as Down Syndrome (trisomy 21). The chorionic villi are finger-like projections in the placenta, a needle is inserted through the cervix or injected to get a sample of the cells. This sample can also test for multiple other genetic disorders like thalassemia, cystic fibrosis, and Tay – Sachs disease just to name a few.

Amniocentesis

This is a diagnostic test done during the second trimester (16-20 weeks) of pregnancy, where a sample of amniotic fluid is drawn from the womb. Amniocentesis can detect many genetic disorders that include trisomy 18, trisomy 13, Down Syndrome (trisomy 21), and other chromosomal abnormalities like Turner’s Syndrome and Klinefelter Syndrome. Other single gene diseases can also be detected through amniocenteses, such as sickle cell disease and cystic fibrosis. Neural tube defects such as spina bifida and anencephaly can also be detected.

                                                                    Courtesy: Medical Flox

Why are genetic tests important during pregnancy?

When there was any family history of genetic conditions or previous miscarriages you doctor may suggest having these genetic tests done. Diagnostic tests are also especially important if parents were tested positive carriers of a genetic condition.

Genetic screening for Down Syndrome is usually important for pregnant women aged 35 and older this is because the genetic risk of Down Syndrome increases with maternal age.

As with any form of medical tests, there will be contraindications and risks, always consult your doctor for advice before making any decisions to go ahead with it. One life lost is one too many especially when it comes to your own baby.

]]> http://www.scienceofbiogenetics.com/can-you-or-your-children-inherit-mental-illness/ Mon, 06 Nov 2017 08:24:13 +0000 http://www.scienceofbiogenetics.com/?p=171 Since the human genome project researchers have been on a mission to find genetic links to various aspects of medicine. Many diseases have been found to be linked to the genes that have been passed from your parents this could lead to susceptibility to a variety of diseases.

A breakthrough in research has found that various mental illnesses have genetic links to its predisposition and thus could be inherited by children if their parents or family has a medical history of psychiatric disorders.

Genetic Predisposition to Mental Illness

In 1990, a paper was published by St Clair and colleagues that studied a large family from Edinburgh and discovered that differences at the q21-22 region on chromosome 11 presented genetic susceptibility to mental illness.

This sparked other researchers to further understand if mental illnesses can be passed to the next generation through parents’ genes.

The present research has been done to determine specific genes that are associated with mental illness manifestation in an individual.

Studies have shown that schizophrenia, depression, bipolar disorder have genetic links to its predisposition.

                                                 Courtesy: U.S National Library of medicine

Specifically, DISC – 1 (disrupted in schizophrenia 1) a protein whose gene is located on chromosome 1 was found to show the predisposition to schizophrenia and depression.

A mutated DISC – 1 gene in mice resulted in abnormal DISC – 1 protein formation, which was investigated to be related to a number of cellular activities in the brain, such as, protein interactions at the brain cell network and cell multiplication.

Aberrant formation of DISC – 1 protein thus leads to abnormal brain cell functioning and could predispose the individual to psychiatric disease.

Single nucleotide polymorphisms in the CACNA1C gene was also found to affect susceptibility to major depression disorder (MDD). CACNA1C gene which codes for the alpha 1C subunit of a voltage-dependent calcium channel which means it’s a protein that utilizes changes in cellular voltage for the cell to transport calcium.

Single nucleotide polymorphisms (SNP) are genetic variation in a single nucleotide in a DNA sequence (A, T, C or G) which varies between paired chromosomes. The research was done by Backes. H and colleagues discovered that patients with (Major Depression Disorder) MDD produced more than normal amounts of the CACNA1C protein.

This is especially so if the patient inherited the A allele of a specific SNP position (rs1006737). This variation later led them to observe that there were differences in the prefrontal and cerebellar regions of the brain. These two areas focus on personality development and muscle coordination respectively.

Overcoming Genetic Inheritance with Environmental Factors

Despite the research showing that one can genetically inherit mental illnesses through specific genes, these only show that there is a higher predisposition for individuals if these abnormal genes or SNPs are present.

The environment that a child is brought up in can also influence whether the psychiatric disorder can truly manifest.

This was done through gene-environment correlation studies, it discusses the association between the genotype inherited and the environment the child is brought up can influence the genetic effects of inherited mental illness.

This means that even with the genetic inheritance of genes that influence mental illnesses or family history, exposure to the environment can also play an important role in the development of psychiatric disorders.

With increasing links between genes and mental illnesses being discovered psychiatric genetic counseling has been made available especially if there is the family history of any kind of major psychiatric disorder.

A pilot study was done in 2008 where a group of subjects participated in a psychiatric genetic counseling session for parents of individuals affected with psychotic disorders. This research showed that there was a better understanding amongst the participants that inheriting psychiatric illnesses could be influenced by genes and environment.

So,

Don’t be too worried if there is the history of the psychiatric disease in your family, genetic factors linked to behavior and mental illnesses inheritance can be subdued by environmental exposures.

References

[1]. Backes H, Dietsche B, Nagels A, Konrad C, Witt SH, Rietschel M, Kircher T, and Krug A (2014) Genetic variation in CACNA1C affects neural processing in major depression, Journal of Psychiatric Research, 38- 46

[2]. Nicholas J. Brandon, J. Kristy Millar, Carsten Korth, Hazel Sive, Karun K. Sing, and Akira Sawa (2009) Understanding the Role of DISC1 in psychiatric disease and during Normal Development, Journal of Neuroscience, 29 (41) 12768-12775; DOI: https://doi.org/10.1523/JNEUROSCI.3355-09.2009

[3]. St Clair, D. Blackwood, W. Muir, M. Walker, D. St Clair, W. Muir, A. Carothers, G. Spowart, C. Gosden, H.J. Evans, Association within a family of a balanced autosomal translocation with major mental illness, In The Lancet, Volume 336, Issue 8706, 1990, Pages 13-16, ISSN 0140-6736, https://doi.org/10.1016/0140-6736(90)91520-K.  (http://www.sciencedirect.com/science/article/pii/014067369091520K)

[4] Knafo, A., & Jaffee, S. (2013). Gene-environment correlation in developmental psychopathology. Development and Psychopathology, 25(1), 1-6. doi:10.1017/S0954579412000855

[5] Austin, J. C., and Honer, W. G. (2008), Psychiatric genetic counseling for parents of individuals affected with psychotic disorders: a pilot study. Early Intervention in Psychiatry, 2: 80–89. doi:10.1111/j.1751-7893.2008.00062.x

[6] Jaffee, S., & Price, T. (2007). Gene-environment correlations: a review of the evidence and implications for prevention of mental illness. Molecular Psychiatry, 12(5), 432–442. http://doi.org/10.1038/sj.mp.4001950

Before reading more about How two brown-eyed parents have a blue-eyed child? I suggest you go through below post to understand more about eye color genetics.

Genetics of Eye Colour: What does your eye colour says?

How is eye color genetically inherited?

The interactions between various genes have been found to determine color pigmentation in humans. However, specifically, HERC2 and OCA2 genes located on chromosome 15 are associated with eye color. Different studies have shown that specific Single Nucleotide Polymorphism (SNP) position on the OCA2 gene determines the presence of brown or blue eyes.

The research was done to find out the genes that are associated with human pigmentation showed that HERC2 SNP rs12913832 was statistically significant when tested for the association with eye color. Within this SNP two alternative forms of a gene (allele) C and T DNA bases determines the color of the eye.

Since all chromosomes come in pairs, possible variations of this gene would be CC, TT (homozygous), and CT (heterozygous) with one allele being inherited from each parent.

Statistical results from a research done by Branicki et. al. (2009) showed the CC gene expressed 88.9% of blue-eyed subjects, CT and TT gene both expressing brown/black-eyed subjects with 84.4% and 15.6% respectively.

Is there a possibility that two brown-eyed parents of having a blue-eyed child?

As research has shown that genes are associated with eye color, we can now predict if it is possible that two brown-eyed parents to have a blue-eyed child. This can be easily determined by using a Punnett’s square, where possibilities of the parent genotypes are used to check the probability of what genotype a child would inherit.

Since both parents are brown-eyed their genotypes would either be CT and CT, TT and TT, or CT and TT

Conclusion: If both brown-eyed parents are both heterozygous CT there would be a 25% chance that their child would inherit the CC gene and have blue eyes.

Conclusion: If both brown-eyed parents are both TT none of their children would have blue-eyes. 

Conclusion: If both brown-eyed parents are either CT or TT none of their children would have blue-eyes. 

From the research by Branicki et. al. (2009), we have done a Punnett’s square test and shown that both parents have to be heterozygous CT in order for their child to have 25% probability of inheriting blue eyes.

This was also discussed in an article by www.science daily.com where they highlighted that it is possible for brown-eyed parents to have a blue-eyed child.

So don’t go running out to do paternity tests just yet when you see your child with a different eye color. He/she might just have been the 25% of the gene pool having blue-eyes even though you and your spouse have brown-eyes.

References for more info :

Branicki, W., Brudnik, U. and Wojas-Pelc, A. (2009), Interactions Between HERC2, OCA2 and MC1R May Influence Human Pigmentation Phenotype. Annals of Human Genetics, 73: 160–170. doi:10.1111/j.1469-1809.2009.00504.x

Springer. “Blue Eyes — A Clue To Paternity.” ScienceDaily. ScienceDaily, 23 October 2006. <www.sciencedaily.com/releases/2006/10/061023193617.htm>.

Sturm, R. A. and Larsson, M. (2009), Genetics of human iris colour and patterns. Pigment Cell & Melanoma Research, 22: 544–562. doi:10.1111/j.1755-148X.2009.00606.x

Rhesus factor determines if the blood type is positive (+) or negative (-). Blood type is considered as A+ve or B+ve or O+ve if they have rhesus factor. People who don’t have rhesus factor are considered to have negative blood type such as O -ve. An O negative blood type is considered to be a universal donor since it contains nothing that would appear foreign to someone else’s blood. People with AB positive blood type is considered as universal recipients as they will not react to A, B, or O blood, and can receive a transfusion from a donor with or without the Rhesus antigen.

Now coming back to our question: Can an O positive mom and an O positive dad have a child with another blood type?

In ABO blood group system, If your mom is O positive and dad is also an O positive blood type then the child will have O blood type. Let’s try to understand this based on how alleles are passed on from parents to children.

Here, father and mother have O Blood group which means they have IoIo alleles. So In all combinations child will inherit Io from father and Io from the mother so which will become IoIo for the child. So in ABO blood group, a child will have O blood group. 

Read more on blood type inheritance: If Father has Blood Group A and Mother has Blood Group B , What will be the blood group of children ??

Let’s understand this again: Can an O positive mom and an O positive dad have a child with another blood-type?

Yes, It is possible in one of such case. One of the known couples have kids of blood type A and blood type B even though both parents are of type O blood. Though none cheated on each other still they had kids of different blood group than O. It’s strange but true. How did it happen? How could the child have different blood group even though parents belonged to O positive?

To understand this, we should understand how blood type detection test is done?

Blood group is detected by a simple laboratory test. In which blood sample is collected and made to react with different reagents. A person’s blood group is determined by different antigens. In ABO blood group people can have A blood type, B blood type, AB blood type and O blood type.

When sample blood group is exposed to reagents, the reaction may or may not occur. If blood has antibodies to particular blood group then reaction happens and it cannot belongs to that blood group. If blood group lacks A antigen then it belongs to B blood type. If blood group lacks B antigen then it belongs to A blood type. If blood group lacks antigen A and antigen B then it belongs to blood type O.

Blood type O also looks like Bombay blood group.  It is because Bombay Blood Group will not have antigen A and antigen B, so lab technicians will think that it belongs to blood group O unless blood sample is made to test against H antigen, Bombay blood group doesn’t contain H antigen too but people with blood type O contains H antigen. So it’s because of the way blood type is detected, it is more likely that Bombay blood group is misdiagnosed as blood group O. this Bombay blood group is also known as HH blood group.

Read More on to know Bombay Blood Group details:  Do you know Bombay Blood Group?

A person needs to have H gene in order to make A protein or B protein.  ABO gene codes for proteins that turn the H protein into A or B.  Since Bombay blood group type people lack protein H and their ABO gene cannot produce A or B . In such person even though the ABO gene may actually contain A  but since H protein is not there A might not be expressed. Or they may even have B gene but since again H is not there B might not have expressed too. So it’s more likely they look like O blood group type.

If either one of these couples belongs to Bombay phenotype and their child will express into other blood groups. Let’s find possible blood group of children when one belongs to Bombay blood group and other is actually O.

So in summary, one of the parents cannot make H protein which is required to produce A or B. but one of their ABO genes can code for either B or A protein which can be passed on to its child.

If the father has Bombay blood group and mother is having blood group O then the child can have following offsprings.

Assuming father can able to code for B but its not expressed because of broken H gene. So in that case we can see child having either blood group B or blood group O.

Assuming father is able to code for A but its not expressed because of broken HH gene. Then the child will have blood group of A or blood type of O.

Assuming father is able to code for A and B but its not expressed because of broken HH gene, then the child may have blood group A or blood group B or blood group O.

Hence, even if parents are detected with blood type O they may still have another blood type only when one of them belongs to Bombay blood type in real.

I understood her concern and what really made me think of her question was Why part. I calmly asked her, Do your hubby also smoke sometime ? as per my expectation, her answer was Yes, sometimes nowadays. So, Is it because since her husband smokes, her son also started smoking? Is it because he inspired from his dad ? or is it because he felt it is okay to smoke as his dad smokes ? or Is it because Smoking is Genetic?

We did a crowdsource open survey from interested candidates from the age group of 12- 50 yrs with the help of one of survey company. Though we knew the genetics behind the habit of smoking, I just wanted to make sure that it is actually what genetics says!

Some of the survey questions are here:

After analyzing the survey from all the candidates we found some interesting facts

1. We found most of the smoker’s father was smoker too (17342 out of 25000)
2. We found most of the smoker’s mother was not a smoker.
3. We found most of the smokers tend to take more risks or ( adventures) than non-smokers
4. We found most of the smokers felt the need for smoke regularly or frequently.

Let’s understand the genetics behind the habit of smoking.

How is Smoking Genetic? How child inherit smoking from its father’s?

In order to explain the overview of how the habit of smoking is genetic, I would like to stick to our above findings.

People start smoking in different ways, one is they just want to try how it feels? they always have curiosity and want to see what happens after smoking, sometime’s their friends asks them to try and go for it. sometime’s it’s for fun. Children always tend to do what their parents does/did. Especially when the child enters adolescence phase then its role of parents becomes very critical. If the child knows that their father also smokes and get the feeling that nothing happens because of smoking, then they feel motivated, inspired and feel secure that nothing happens as their father is already doing it.

In human chromosome 11 is coded by Dopamine Receptor D4 gene which is known as DRD4. This gene has 2-11 repeats. DRD4 protein is expressed in many regions of the brain. Mutations in DRD4 gene can lead to major disorders related to brain, behaviors abnormality, addictive behaviors or other psychological disorders.

DRD4 -4R and DRD4-7R repeats variants of this gene highly influence the behavior of taking risks knowingly. Risk taking can be adventure sports, thriller games, thrill seeking activities, mountain climbing, stunt racing, speedy races, or some kind of risks which can vary from people to people. Among all that Smoking is one of popular risk that people would like to take up knowing that it is not good for your health. The frequency of repeats of alleles in DRD4-4R repeats are 65.1% and that of DRD4-7R repeats are 19.2%. But the amount of risk taking is more in the people who has DRD4-7R repeats than that of DRD4-4R repeats.

So if you are the smoker and has DRD4-7R or DRD4-4R genes, then it’s more likely that your child will inherit the habit of smoking. Though DRD4-7R genes lead to many other disorders. But as long as science proves to be right and if you have above-said genes then it’s more likely that your child will end up being smoker.

Let’s understand how these smokers get addicted to smoking?

When people start to smoke, they start to consume nicotine. They say it gives them pleasure. Smoking gives them pleasure because of nicotine’s action on the brain. Nicotine increases the level of the neurotransmitter called dopamine. They also cause the release of other neurotransmitters and hormones that affect your mood, memory, and more. 

Dopamine is the one which is involved in producing feelings of pleasure. So as and when you smoke, nicotine amount stimulates the dopamine and you start to feel good and relaxed in your own way.

You had a smoke now and you feel like to have another smoke only when the feeling of pleasure has vanished. Means, as long the feeling of pleasure remains in you then the necessity of next smoke is less.

Cytochrome P450 2A6 is a gene which helps in the metabolism of nicotine. Means, CYP2A6 (Cytochrome P450 2A6) is responsible for the oxidation of cotinine and nicotine amount present in the body. So the presence of CYP2A6 will get rid of nicotine from the body.

So once CYP2A6 removes nicotine from the body then the need for smoke increases. So this makes another smoke and another after and it goes on in the smoker and making them addicted to smoking.

Well, you have seen some people who actually start to smoke but they don’t get addicted to it. Even they quit smoking easily. Few people smoke very very rarely, may be at parties or when they are with friends. It is because they will have a slow metabolism for nicotine because of the different variant of CYP2A6 gene.

So, in short, the summary is, If your child has inherited Cytochrome P450 2A6 and Dopamine Receptor D4 -repeats 4 or Dopamine Receptor D4-repeats 7 genes then he will end up smoking like you do.  

Quit Smoking Now, It’s good for you and for the generations of yours !!

these days many people who face complications for becoming pregnant goes for in-vitriol fertilization. most of cases of in-vitriol fertilization gives us twins !!

are you twins?

The idea that we normally get when we listen to the word twins is two identical people; looking alike and born by the same pregnancy. Yes, it’s right.

So what are twins ??

Twins are two offspring produced by the same pregnancy. They may be either identical or even look different. Based on the formation of zygote, twins can be classified into ‘Fraternal twins’ and ‘Identical twins’.

Identical twins are developed from the same zygote which splits and then forms into two embryos. Hence it is also known as ‘Monozygotic twins’. Fraternal twins are developed from two different eggs and are known as ‘Dizygotic twins’.

How twins are formed ??

Each egg is fertilized by separate sperm cells. Since fraternal twins are separately fertilized eggs, they develop two separate amniotic sacs, placentas and supporting structures. Thus they are different from each other and are essentially two ordinary siblings who happen to be born at the same time.

But,

Identical twins may or may not share the same amniotic sac, depending on how early the single fertilized egg divides into two.

The three possible pairs of twins are

1. Male-male twins
2. Female-female twins
3. Male-female twins

Normally, same gender twins are identical twins and male-female twins are fraternal twins. But not essentially true always.

Since, same gender twins can have same DNA, they are identical twins. Male-female twins differ by the DNA and are usually fraternal twins.

Sometimes, male-female twins can also be identical twins. It’s a rare case.This is the result of an error that generally happens in the early stage of pregnancy. In this case, initially the twins will be a pair of males (sharing XY chromosome), which then change to become a male and female pair. This occurs when one half of the split fertilized egg loses a copy of its genetically encoded Y-chromosome, resulting to male-female twins.

More about Fraternal Twins

Fraternal twins happen when mom releases two separate eggs, may be at the same time or different times during her cycle and these two eggs are fertilized by two separate sperms forming two embryos. These two embryos are developed into separate babies. Thus, fraternal twins are just like any other siblings born at the same time, having only a small chance of same chromosome profile. Like any other siblings fraternal twins may or may not look similar.

How are fraternal twins conceived?

The two most common ways that fraternal twins conceived are;

1. Superfecundation and
2. Superfetation

Superfecundation- it happens when a woman ovulates more than one egg during her cycle and the eggs are fertilized by two sperms. This may be due to heredity. Woman may have inherited a gene that causes hyperovulation (woman releases more than one egg during her regular cycle). Many fertility drugs can also cause hyperovulation.

Superfetation- it happens when mom is already pregnant when she ovulates and release another egg. The duration gap may be as long as 24 days from the release of first egg to the second egg. A different sperm will fertilize the second egg. In this instance, the babies will be delivered at the same time but with different sizes and development stages. In-vitro-fertilization is also a form of superfetation.

Fraternal twin are also more common for older mother, woman over the age of 35 with double twinning rates. Not only about twins, there are also chances of having triplets and multiples. This is quite common among animals. In humans, it’s rare. But do happen.