a) Give three reasons why a diploid individual will not produce a gamete with ex
ID: 273343 • Letter: A
Question
a) Give three reasons why a diploid individual will not produce a gamete with exactly the same DNA as either of the haploid gametes that fused to form that individual. Explain your answers [6 marks] b) What characteristic of the human X chromosome and Y chromosome allows them to pair up [2 marks] during meiosis in males? c) Non-disjunction of the X chromosome during meiosis in human females can create gametes containing two X chromosomes. Explain why females formed by fertilisation of such gametes [3 marks] are functionally normal.Explanation / Answer
a) Diploid individuals will not produce a gamete with exactly same DNA as either of the haploid gametes that fused to form parent DNA , because during meiosis both the gamet separate according to law of independent assortment and both of them don't affect one another.
b) Human X and Y chromosomes determine the biological sex of a person, with XX specifying female and XY specifying male.
Although the Y chromosome contains a small region of similarity to the X chromosome so that they can pair during meiosis, the Y chromosome is much shorter and contains many fewer genes.
C) females formed by fertilization of nondisjunction of x chromosomes are functionally normal is is called x- inactivation.
X-INACTIVATION :-
-Men have only one X chromosome. Women have the same dosage for a different reason, they shut down one of their two X chromosomes in a process called X-inactivation.
-In this process an X chromosome is compacted, to make a small, dense structure called a barr body. Most of the genes on the Barr body are inactive, meaning that they are not transcribed.
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