The sex chromosomes in humans are usually females XX and males XY - VCE - SSCE Biology - Question 27 - 2013 - Paper 1
Question 27
The sex chromosomes in humans are usually females XX and males XY.
In each of the somatic cells of a normal female, only one of the X chromosomes is active. The oth... show full transcript
Worked Solution & Example Answer:The sex chromosomes in humans are usually females XX and males XY - VCE - SSCE Biology - Question 27 - 2013 - Paper 1
Step 1
A. XX would have no Barr bodies in each of their somatic cells.
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Answer
This statement is incorrect. In a normal female (XX), there is one active X chromosome and one inactive X chromosome that forms a Barr body.
Step 2
B. XXX would have two Barr bodies in each of their somatic cells.
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Answer
This statement is correct. In a typical female with three X chromosomes (XXX), there are two inactive X chromosomes, resulting in two Barr bodies.
Step 3
C. XY would have one Barr body in each of their somatic cells.
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Answer
This statement is incorrect. In a typical male with XY chromosomes, there is only one X chromosome, which is active, and therefore there are no Barr bodies.
Step 4
D. XXY would have two Barr bodies in each of their somatic cells.
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Answer
This statement is correct. An individual with XXY chromosomes has one active X chromosome and one inactive X chromosome, resulting in one Barr body.
