Question

An organism will be biologically male if the 23rd chromosome pair in the zygote is:

a) XX
b) X
c) XY
d) Y"

Answer 1

In mammals, including humans, a biologically male organism has one X and one Y chromosome (XY) in the 23rd chromosome pair, which is the correct answer to the student's question.

Step-by-step explanation:

The sex of an organism, specifically a mammal, is determined by the sex chromosomes present in the 23rd pair of chromosomes. In mammals such as humans, a biologically male individual has one X chromosome and one Y chromosome, represented as XY. Therefore, the correct answer to the question is 'c) XY'. Females, on the other hand, possess two X chromosomes, represented as XX. It's important to note that in birds, the system is different where ZZ represents male and ZW represents female.

Sex-linked inheritance explains that males have XY chromosomes, while females have XX chromosomes. Gametes formed in male mammals carry either an X or Y chromosome resulting in the possibility of either male or female offspring after fertilization with female gametes that always carry an X chromosome.

Some irregularities such as nondisjunction during meiosis can lead to different combinations like XXY, XYY, and XO, which are various forms of chromosomal intersex conditions.