BIOLOGY

JAMB 2006 - Question 19

Biology 2006 JAMB Past Questions - Question 19: The two normal types of sex chromosomes are

Choose the most appropriate option for the gap .
The two normal types of sex chromosomes are
A:
B:
C:
D:
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Correct Answer

D

Explanation

D XX sex chromosomes are for the females while the XY sex chromosomesare for males. Option B shows a male suffering from Klinefelter's syndrome (XXY) because of thefailure of the two sex chromosomes XX to separate during gamete formation infemales. Thus, if an egg with the two XX sex chromosomesis fertilized by a sperm with Y chromosome, an individual with thischromosomes combination results. Three X- chromosomes (XXX) results In asterile female. This is caused by inability of chromosome number 21 to separatein the female during gamete formation and is fertilized by sperm with Xchromosome.