Tuesday, 18 February, 2020

The Cool Reference Guide

IVF AND X-LINKED GENETIC DISEASES


In vitro fertilisation, or IVF, is one of the solutions introduced to many couples who are challenged in childbearing. It involves the natural process of fertilising a mature human ovum by a viable sperm, but in a test tube. It all seems fantastic until talks of IVF and X-linked genetic diseases arise in the picture. 

What remains in question

The intent behind IVF assistance, giving couples the chance to become parents, is noble. However, where should the line be drawn in intercepting the way of nature when considering the risks concerning sex-linked genetic diseases? 

The thing is, when these couples seek this kind of assistance, they pay a lot of money for success. This involves multiple series of in vitro fertilisation and mindful analysis of hereditary disease, ailments, conditions, and disorders. These processes are continuously questioned ethically. In order to avoid sex-linked genetic diseases, gender preference is often part of the procedure.

Then, these two issues remain in question. What will happen to the other fertilised eggs that were not chosen? What will happen to the gender ratio concerning gender specification? 

Baby gender selection is often only given as an option to couples who have an extremely high susceptibility to gender-specific diseases. In turn, the remaining eggs or the high-risk ones will be kept frozen for future use for a certain storage fee. It will not be thrown away or disregarded to any extent without the couple’s consent. 

How does one become susceptible to sex-linked diseases?

Female babies carry XX chromosomes, and male babies carry XY chromosomes. Besides being determinants of a baby’s gender, it also passes dominant and recessive traits, including certain sex-linked diseases. It means that not only normal genes are passed along but also abnormal ones in which the matching of both parents’ genes come to play.

The abnormal gene is passed along if it was inherited dominantly from one parent. All kids are just ‘susceptible’ if only one parent has the same dominant inheritance. 

This may also be applied in the same way concerning recessive traits. Offspring becomes less susceptible if either one is just a carrier. However, depending on matching genes, the effects of a disease may come out mild, or the offspring may just end up as a carrier.

What are the most common X-linked genetic diseases?

X-linked diseases are most often seen among males. Since they only have one X chromosome, this single recessive gene will cause the abnormality or the disease. While it has Y for the other half, it doesn’t need another chromosome to let the abnormality surface, making them unprotected from diseases. Examples of these X-chromosome recessive genes are:

Haemophilia – Haemophiliacs are susceptible to bleeding because it is a disease in which a certain blood-clotting factor is missing. This makes it hard for a wound to close up. It is not common among females since it holds 2 X chromosomes, one from the mum and one from the dad. By pattern, both parents should have this X-recessive trait for the disease to be passed to the female offspring, therefore reducing the chance of it happening. If the male offspring, being made up of XY chromosomes, receives the affected gene from the mum, they will have the disease since it is enough to cause it. Since this is X-linked, dads cannot pass this abnormal gene to their sons.

Muscular Dystrophy – Duchenne Muscular Dystrophy, to be exact, is an X-linked recessive trait that causes rapidly progressive muscular dystrophy. This occurs mostly among boys who hold one copy of an affected X chromosome from both parents. If the X-chromosome has the DMD gene mutation, affectation is assured. Since female offspring need both X chromosomes to have acquired the DMD gene mutation, they just end up as a carrier most of the time. Hence, this disease, which may weaken the heart and lungs since they are all muscles, relies greatly on family history. Male offspring that are born with a changed DMD gene copy will be affected since they hold a Y chromosome, not having that other X chromosome back-up. DMD condition affects one male in every 3500 births worldwide. If a male infected with DMD were to reproduce, none of his sons would be affected, but all of his daughters would become carriers of the disease.

Is it worth it?

In vitro fertilisation remains the beacon of hope to many reproductively-challenged parents. It is not exempted from having its risks and baby gender selection costs are high. Always make sure to do thorough research before participating in IVF. 

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