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?
[UPSC Civil Services Exam – 2021 Prelims]
(a) 1 only
(b) 2 only
(c) Both 1 and 2
(d) Neither 1 nor 2
Answer: (c)
Explanation:
Mitochondrial replacement therapy (MRT)
- It is a type of in vitro fertilization (IVF) that involves the replacement of a woman’s unhealthy mitochondrial DNA (mtDNA) with healthy mtDNA from a donor. Various techniques are used for MRT, including spindle transfer (ST), pronuclear transfer (PNT), and polar body transfer (PBT).
- Pronuclear transfer is an MRT technique that involves fertilizing two zygotes in vitro.
- Maternal spindle transfer (MST) is an MRT technique that involves selective reproduction similar to prenatal diagnosis and pre-implantation genetic diagnosis (PGD) and is carried out before fertilization. Statement 1 is correct.
Mitochondria
- Mitochondria are the only organelles, besides the nucleus, that contain circular DNA and genes in animals. However, sperm contains a minimal amount of mitochondria and mitochondrial genes. As a result, mitochondrial genes are solely inherited from the mother by the offspring. This means that a father with a mitochondrial gene defect cannot pass the condition onto his children. Statement 2 is correct.
