Question

(a) (i) Write the karyotype and the genetic disorder of an individual who has developed from a zygote formed from an ‘XX’ egg fertilized by a ‘Y’ sperm.
(ii) Mention any two symptoms of this genetic disorder.
(iii) Write the possible reason that leads to the formation of this ‘XX’ egg.
OR
(b) In case of any dispute, a very small sample of tissue or even a drop of blood can help us to determine the paternity of a child. Provide a scientific explanation to substantiate the statement.

Hint:

(a) (i) Klinefelter syndrome occurs when a male has an extra X chromosome. The typical karyotype is XXY instead of XY.
(ii) Klinefelter syndrome leads to infertility and distinctive physical features, such as tall stature and longer limbs, due to an extra X chromosome.
(iii) Non-disjunction during meiosis can result in gametes with an abnormal number of chromosomes, leading to genetic disorders like Klinefelter syndrome.
(b)

Answer 1

(a) (i) - Karyotype: The karyotype of this individual will be XY, as the egg provides the X chromosome and the sperm provides the Y chromosome.
- Genetic Disorder: The individual may have Klinefelter syndrome, a disorder caused by the presence of an extra X chromosome (XXY), leading to male infertility and other physical and developmental features.
(ii) Two common symptoms of Klinefelter syndrome are: 1. Infertility: Due to underdeveloped testes and reduced sperm production. 2. Tall stature and long limbs: Affected individuals are typically taller than average, with longer arms and legs.
(iii) The formation of an XX egg can occur due to a failure in meiosis, specifically during oogenesis. This error, known as non-disjunction, leads to an egg with two X chromosomes instead of just one.
OR
(b) The DNA in a small sample of tissue or blood contains unique genetic markers (alleles) inherited from both parents. By comparing the DNA of the child with the DNA of the alleged father, we can identify matching markers that confirm or rule out paternity. This process is called DNA fingerprinting.