Genetic Disorders

1. The X-chromosome linked colour blindness affects the ability to detect

The X-chromosome linked colour blindness affects the ability to detect the difference between which of the following lights ?

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Green light and red light
Yellow light and blue light
Blue light and violet light
Yellow light and red light
This question was previously asked in
UPSC CISF-AC-EXE – 2018
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X-chromosome linked colour blindness is most commonly red-green colour blindness. This condition affects the photoreceptor cells in the eye (cones) that are sensitive to red and green light, making it difficult to distinguish between these colours.
X-linked colour blindness primarily impairs the ability to distinguish between red and green colours.
Colour blindness is often inherited and is much more prevalent in males because the genes responsible for the most common forms are located on the X chromosome. Females have two X chromosomes, so a functional gene on one X chromosome can often compensate for a non-functional one on the other, whereas males only have one X chromosome.

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2. In the context of hereditary diseases, consider the following statemen

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

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  • 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
This question was previously asked in
UPSC IAS – 2021
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Statement 1 is correct, and statement 2 is correct.
– Statement 1: Mitochondrial Replacement Therapy (MRT), including Pronuclear Transfer or Maternal Spindle Transfer techniques, aims to prevent the transmission of mitochondrial diseases from mother to child. These procedures involve transferring the nucleus from the affected mother’s egg (or zygote) into a donor egg (or zygote) that has had its nucleus removed but retains healthy mitochondria. This can be performed either before or after fertilization (in vitro fertilization).
– Statement 2: Mitochondria, organelles responsible for energy production within cells, contain their own DNA (mtDNA). In humans, mtDNA is almost exclusively inherited from the mother because the egg contributes the vast majority of cytoplasm (containing mitochondria) to the zygote, while the sperm contributes primarily nuclear DNA. Therefore, mitochondrial diseases are maternally inherited.
Mitochondrial diseases are a group of chronic, genetic disorders that occur when mitochondria fail to produce enough energy for the body to function properly. MRT is a relatively new and complex technique with ethical and regulatory considerations, approved in some countries under specific conditions.

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3. Which one of the following examples of genetic-disorder or disease is

Which one of the following examples of genetic-disorder or disease is due to the numerical abnormalities in the sex chromosome ?

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Turner's syndrome
Down's syndrome
Haemophilia
Alkaptonuria
This question was previously asked in
UPSC Geoscientist – 2024
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A
Turner’s syndrome is a genetic disorder affecting females, caused by the complete or partial absence of one X chromosome (monosomy X, 45,XO). This is a numerical abnormality involving the sex chromosome.
Down’s syndrome is caused by trisomy of chromosome 21, an autosomal numerical abnormality. Haemophilia is an X-linked recessive disorder resulting from a mutation in a gene on the X chromosome, not a numerical abnormality of the chromosome itself. Alkaptonuria is an autosomal recessive metabolic disorder.

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