Question

How is the sex of a newborn determined in humans?
a. The sex of the individual is genetically determined.
b. The sex of the individual is phenotypically determined.
c. The sex of the individual is physiologically determined.
d. None of the above.

Answer 1

Hint: Chromosomes play the main role in determining the sex of a baby. Males and females, each have a pair of sex chromosomes. Males have X and Y chromosomes and females have two X chromosomes. The way these chromosomes get inherited by the progeny determines its sex. There is always a 50-50 chance of having both genders.

Complete answer:
- The sex of a newborn is genetically determined in humans.
- Males have X and Y chromosomes. This means that they have two types of sperms, each possessing a particular chromosome.
- Females have X and X chromosomes. This means that their egg cell can only have an X chromosome.
- So, depending on which type of sperm fuses with the egg cell (having X chromosome), the sex of the baby can be determined.
- If the egg fuses with a sperm having an X chromosome, the sex of the offspring would be female (XX).
- If the egg fuses with a sperm having a Y chromosome, the sex of the offspring would be male (XY).

There are some disorders and abnormalities associated with the number of chromosomes.
- Turner syndrome is a genetic condition in which females are either partially or completely missing the second X chromosome (X0). People with this disorder have a short stature, webbed neck, swollen hands, and low hairline.
- Klinefelter syndrome arises when there is an extra X chromosome in males (XXY). This results in infertility, weak muscles, breast development, and less body hair.

Hence, the correct answer is option (A).

Note: There is always an equal chance for both genders. Also, gender analysis is an important method as it can help the parents to understand and prevent prospective birth defects related to gender.