The 47th chromosome has 21 extra genes and XY refers to gender There is an extra chromosome in the 21st pair and XY refers to gender The 21st chromosome has additional genetic material and XY refers to location of the gene The number 47 refers to the type of test and 21 refers to the number of abnormal cells identified. true/false

The question is incomplete but assuming that the person is suffering from Down syndrome and is not able to understand the meaning of 47, XY, +21.

2. There is an extra chromosome in the 21st pair and XY refers to gender

Explanation:

In humans, the normal number of pairs of a chromosome is 23 which means there are 46 chromosomes.  Sometimes, non-disjunction during gamete formation creates or subtracts an additional copy of chromosomes as a result of which the gametes possess an extra copy of the chromosome.

In the given question, the same condition has been observed that is the person has 47, XY, +21 which is known as the Down syndrome.

The 47, XY, +21 in simple terms can be understood in the following way:

1. 47: Shows that there is one extra copy of chromosome

2. +21: means that the extra copy is of 21st pair of chromosome

3. XY: is a chromosome pair that determines the gender.

Thus, the selected option is correct.

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