
In the context of hereditary diseases, consider the following statements:
- Passing on mitochondrial diseases from parent to child can be prevented by mitochondrial replacement therapy either before or after in vitro fertilization of egg.
- A child inherits mitochondrial diseases entirely from mother and not from father.
Which of the statements given above is/are correct?
- 1 only
- 2 only
- Both 1 and 2
- Neither 1 nor 2
Explanation
Statement 1 is correct
- Mitochondrial donation (sometimes called mitochondrial replacement therapy) is a group of techniques that allow women whose eggs contain unhealthy mitochondria to have healthy children. There are several ways to undertake mitochondrial donation, but, in all cases, the goal is to create an embryo with the nuclear genome of the mother and father, but the mitochondria (and therefore the mitochondrial DNA) of a donor.
- There are two different methods and both use In Vitro fertilisation (IVF). In the first, the nuclear genetic material from the mother’s egg is transferred into a donor egg which has had its own nuclear genetic material removed. This egg is then fertilised with the father’s sperm to create an embryo. The second technique is identical except it takes place after fertilisation, in a single-celled embryo rather than an egg. It cannot cure people with existing mitochondrial disease or prevent mitochondrial disease caused by a mutation in nuclear DNA.
Statement 2 is correct
- Mitochondria are inherited maternally, meaning they are passed from the mother to the child. The sperm provides almost no cytoplasm (and hence no mitochondria) to the fertilized egg.

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