Prelims 2021

Q. In the context of hereditary diseases, consider the following statements:

1.Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of the egg.
2.A child inherits mitochondrial diseases entirely from mother and not from father.

Which of the statements given above is/are correct?
a) 1 only
b) 2 only
c) Both 1 and 2
d) Neither 1 nor 2
Correct Answer: c) Both 1 and 2

Question from UPSC Prelims 2021 GS Paper

Explanation : 

Mitochondrial Replacement Therapy and Prevention of Mitochondrial Diseases

Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy (MRT), also known as mitochondrial donation. This is a special form of in vitro fertilization in which the mitochondria from a donor egg are used to replace those of the mother. This technique involves transferring the nuclear DNA from the mother’s egg or embryo into a donor egg or embryo that has healthy mitochondria and whose own nuclear DNA has been removed. This can be done before fertilization (as in maternal spindle transfer or germinal vesicle transfer) or after fertilization (as in pronuclear transfer). The resulting embryo has the nuclear DNA of the intended parents but the mitochondrial DNA of the donor, thus preventing the transmission of mitochondrial diseases from the mother to the child.

Inheritance of Mitochondrial Diseases

A child inherits mitochondrial diseases entirely from the mother and not from the father. Mitochondria are unique organelles within cells that have their own DNA, known as mitochondrial DNA (mtDNA). Unlike nuclear DNA, which is inherited from both parents, mtDNA is typically inherited exclusively from the mother. This is because the mitochondria in the sperm are usually destroyed or degraded after fertilization, and thus do not contribute to the embryo’s mitochondrial pool. Consequently, if a mother has a mitochondrial disease (caused by mutations in her mtDNA), there is a risk that she can pass it on to her children, while fathers do not pass on mtDNA to their offspring, and thus do not transmit mitochondrial diseases.

Therefore, the correct answer is “Both 1 and 2“.

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