concise verbal or mathematical statement of a relation that expresses a fundamental principle of science, like Newton's law of universal gravitation.
Derives from the fact that bacteria are exploited by humans in a number of beneficial ways
Answer:
At meiosis II in the mother
Explanation:
Both the parents have normal vision but both the sons are colorblind. Since colorblindness is X linked recessive disorder, the sons have obtained the allele for colorblindness from mother. This makes the mother carrier for colorblindness. The genotype of the mother is X^cX. The young man with Klinefelter syndrome is colorblind which means that he is homozygous recessive for the allele of colorblindness. His genotype is X^cX^cY. Since this man has obtained two copies of the allele of colorblindness, the mother must have experienced nondisjunction at meiosis II during gamete formation.
Anaphase-II of meiosis II separates and segregates the sister chromatids (now called daughter chromosomes) to opposite poles. Failure of segregation of two copies of X^c chromosome of mother to opposite poles and their distribution to the same egg cell resulted in the formation of an egg with two copies of X^c chromosome. Fertilization of this egg with a sperm carrying "Y" chromosome as sex chromosome resulted in a zygote with X^cX^cY that developed into the man with Klinefelter syndrome and colorblindness.
