GENOTYPE AND GENOTYPE COMPATIBILITY

Dr. Adesoye Tosin
Posted February 23, 2020 from Nigeria

 

 

Last week, I watched a discussion among some group of people about genotype compatibility and possible solutions  to incompatibility on a reality show about finding love. They suggested that the genotype of an embryo with sickle cell disease can possibly change if carried by a surrogate mother with genotype AA.I couldn't believe the level of ignorance so  I deemed it fit to discuss genotype and genotype compatibility again on my page. I will make this as understandable as possible.

GENOTYPE  

  Genotype is the genetic constitution of every individual . Your genetic constitution are the genes you inherit from both of your biological parents, you get a part from your mother and a part from your father, the part becomes a whole that makes you.

Examples of genotypes include AA,AS,AC,SS,SC,Sβ-Thalassemia etc Your genotype is made up of different HAEMOGLOBIN GENES you inherit from both of your parents. A person with genotype AS can either donate the A haemoglobin gene or the S haemoglobin gene to his/her child , SC can donate the S or the C  while a person with AA genotype can only donate haemoglobin A , a person with SS can only donate the S haemoglobin gene to his/her child etc

TYPE OF HAEMOGLOBIN GENES

NORMAL HAEMOGLOBINS

1. Haemoglobin A which is actually the commonest

2. Haemoglobin A2 , seen in very few people,it is also referred to as normal haemoglobin

3. Haemoglobin F : This is the haemoglobin found in foetus and infants in the first few months of life before it declines. Note: The persistence of haemoglobin F can modify severity of sickle cell disease

ABNORMAL HAEMOGLOBINS are formed as a result of mutations and they include

Haemoglobin S (commonest), C,E, D-Punjab, O Arab etc

SICKLE CELL TRAIT /HAEMOGLOBIN C TRAIT    SICKLE CELL TRAIT: This is the inheritance of a normal haemoglobin A and an abnormal haemoglobin S from your parents giving the AS genotype. Anyone with AS genotype has sickle cell trait

HAEMOGLOBIN C TRAIT: This is the inheritance of a normal haemoglobin A and an abnormal haemoglobin C from your parents giving the AC genotype .

People living with sickle cell Trait or haemoglobin C Trait do not have sickle cell disease . They are asymptomatic most of the time except on some few occasions where they can be symptomatic.

Note: If you have sickle cell Trait (AS) or haemoglobin C Trait (AC)  and you marry/have kids with another partner with the trait or someone with sickle cell disease you can give birth to a child with sickle cell disease.  So anyone with the Trait is advised to have kids with or marry a partner of AA genotype

SICKLE CELL DISEASE

   This is a genetic blood disorder which is characterized by the inheritance of two abnormal haemoglobin genes (one from each parent) and at least one of them being haemoglobin S

Examples

The inheritance of Hamoglobin S  from each of your parents (S + S =SS )

or inheritance of HbS from one of your parents  with inheritance  of another abnormal haemoglobin like C , E , D etc from your other parent  ( S+C = SC , S + E = SE , S + D-Punjab=   SD-Punjab )etc

or the inheritance of hemoglobin S with beta thalessemia (another blood disorder  that is characterized by reduction in production of haemoglobin) S + Beta thalessemia = SBeta thalassemia

These all☝️ indicate you have sickle cell disease

GENOTYPE COMPATIBILITY   Two partners genotype are said to be compatible when they have no possibility of birthing a child with sickle cell disease. They are said to be incompatible when they can possibly have a child with sickle cell disease.   Genotype AA is the universally compatible genotype.

AA +AA= compatible

AA +AS= compatible

AA + SS = compatible

AA + AC= compatible

AS + AS = incompatible

AS+ AC= incompatible

AS + SS = incompatible

AS + SC = incompatible

SS + SS= Incompatible

AC+ SS= incompatible

SC+ SS= incompatible

AS+Sβ-Thal = incompatible

Anyone with any type of sickle cell disease or sickle cell Trait can only be compatible with marrying someone with genotype AA to avoid having a child sickle cell disease

LOVE OR GENOTYPE ?(Just for the Singles)

   This debate has been on forever , some think genotype compatibility should be the first priority in choosing a life partner while others think only love has the final say .

Instead  of answering this question , I prefer to challenge your mind with my own questions,  the answers you get might be what you need to make your decision.

Do you know anything about sickle cell disease?

Are you aware of the manifestations and complications of sickle cell disease?

Do you know the choice you make might be the difference between your child being born with a disease or not?

Do you know even if it's only one of your many children that ends up having the disease, that one child doesn't deserve to be subjected to a life of pain especially when it is your choice to make?

Do you know how much it costs to maintain just one child living with sickle cell disease not to talk of many? Do you know how expensive it is?

Do you know how many families have broken up because of the challenges of raising or losing children with sickle cell disease? Do you know how many  loves have fizzled out because of these challenges?

Is it right to play a gamble over the possible good health of your unborn child?

Are you aware your love and happiness isn't attached to only one person, you can find it somewhere else?

Are you aware your unborn child has a right to good health? Don't you think life has enough challenges already , why add another major challenge to it for your child?

To mention a few,do you know some warriors that do not have it mild have physical disabilities, depression, renal failure,stroke ,multiple organ failure , unfulfilled dreams and aspirations,untimely death because of the complications of sickle cell disease and that could be the fate of another unborn child if you do not take a stand now?

Are you aware the only approved cure for sickle cell disease is not affordable to majority of people living with the disease and for those  that can afford it , not all of them are able to find a match and for those that have had a transplant done, not all of them have gotten a cure, are you aware?

It is up to you to stop the cycle of this virulent disease,  will you?

PRECAUTIONS YOU CAN TAKE IF YOU WANT TO BE WITH A PARTNER OF INCOMPATIBLE GENOTYPE

1. Choosing not to have biological kids or opting for adoption

2.  Preimplantation genetic testing: This can be done if you want to get pregnant via invitro fertilization , before the embryo is implanted, it is investigated for genetic diseases or malformations.  If the embryo has sickle cell disease it won't be implanted . Note: IVF is expensive for an average African and the success rate for IVF is not as high as you might wish

GENOTYPE DETERMINATION TESTS

1.  Amniocentesis and chronic villous sampling : These tests can be used to determine genotype of a foetus early in pregnancy , yes you can determine the genotype of  your unborn child

2. High performance liquid chromatography , isoelectric focussing,  capillary electrophoresis etc can be used to determine genotype and diagnose sickle cell disease in newborns

3. Haemoglobin Electrophoresis: This is the most common way of diagnosing sickle cell disease and knowing your genotype especially in Africa

Note: 1.Do not check your genotype within 3months of blood transfusion , it might alter the result

2. Check your genotype at least twice , if possible thrice because of  cases of genotype misdiagnosis

Do you know your Genotype? Check your genotype today so that we can start making informed decisions. You have a role to play in breaking the sickle cycle. Thanks

           

Comments 10

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Tamarack Verrall
Feb 23
Feb 23

Dear Tosin,
What important and good information and advice you lay out here. Your words are a gift to us all for better understanding, especially to people trying to understand what sickle cell is and how to prevent passing it on. Your community is lucky to have you, as are we all.

Dr. Adesoye Tosin
Feb 23
Feb 23

Thank you ma'am

Anita Kiddu Muhanguzi

Dear Tosin,
Thank you so much for your very educative information on this matter. It is very important for people to always check. However we need to create the awareness. Many people didnt know that they can check.
Thank you for the reminder. Have a lovely day.

Anita Shrestha
Feb 25
Feb 25

Thank you for sharing

Hello, Tosin,

Thank you for sharing this comprehensive information about genotype and genotype compatilibity in relation to Sickle Cell.

I first learned about it from our Sickle Warrior Sister Arrey Echi. Thank you for raising questions to ponder on this condition. Very thought-provoking indeed.

Metiege Noel Eve
Feb 26
Feb 26

Thanks sis thanks for sharing such vital information.

Metiege Noel Eve
Feb 26
Feb 26

Thanks Dr for sharing such vital information on a health challenge that many have been so ignorant about especially in Africa where many deaths of children had been blamed on witchcraft where as some of these kids probably had sickle cell

Gratitude-Love
Mar 06
Mar 06

Dear Tosin,
Thank you for detailed information you shared with us. I truly see your passion and the wisdom you share with us.
Shirin

Doris Ogueri
Mar 12
Mar 12

Thank you Doc. This is a very detailed and important topic. I have witnessed many families wallowing in pains and anguish due to this common mistake of genotype incompatibility in marriage. More awareness need to be done to avoid this avoidable mistake.
God bless you for the work.

Chidimma
Mar 16
Mar 16

Well Taught. Thank you Doctor for sharing. I thought I was in my biology class those days.