Understanding Genetics: JAMB 2021 Solved Questions on Chromosome Probabilities and Sex-Linked Characteristics

Posted on 2025-01-01 by Admin

JAMB 2021 solved questions Chromosome probabilities Sex-linked characteristics Genetic explanations for JAMB

The probability of a woman producing an X-chromosome is

a. 100%

b. 0%

c. 50%

d. 75%

(JAMB 2021)

The answer is A

Explanation: Women have XX chromosomes while Men have XY chromosomes. The probability of a man producing an X-chromosome is 50% while that of a woman producing an X-chromosome is 100%.

The probability of a man producing a Y-chromosome is 50% while that of a woman producing it is 0%

2. A character expressed in a female only when it is homozygous but expresses itself in the male always is

a. sex-linked

b. dominant

c. continuous

d. discontinuous

( JAMB 2021)

The answer is A

Explanation: Sex-linked characteristics are carried by X-chromosomes and are usually recessive. Hence, a male whose X-chromosome is faulty or broken will suffer. A female with a faulty or broken X-chromosome do not have much effect as in males, such female is only a carrier. For a female to suffer from sex-linked character both XX chromosome must be faulty.