Question

Which one is homogametic?
a. Human Child
b. Human embryo
c. Human male
d. Human female

Answer 1

Hint: Males usually have two different kinds of sex chromosomes (XY) and are known as heterogametic sex. Exceptions to this are cases of XX males or XY females, or other syndromes in case of other organisms. The sex of a species possessing similar sex chromosomes is known as Homogametic.

Complete answer:
The sex of an organism is decided by the sex chromosomes, also known to as allosomes. In humans, females generally have 2 X chromosomes while males have a pair of XY chromosomes. The female (in humans and most other mammals) is called the homogametic sex, while the male is called the heterogametic sex.

In humans, the homogametic sex is female. All-female gametes have the same type of sex chromosome: X-chromosome.

In some other animal species, like in some birds and reptiles, the homogametic sex is the male. They possess two Z sex chromosomes. It means all gametes that they produce will bear only a Z sex chromosome.

If we talk about mammals including humans, the female is the homogametic sex i.e. females possess two identical homologous chromosomes (XX) but in males, the heterogametic sex, possesses two homologous chromosomes of different sizes with different genes (XY).

Hence, the correct answer is option (D).

Note: Heterogamesis can lead to the reduced or absent meiotic recombination between the sex chromosomes. And in some species, this extended up to the autosomes, a phenomenon called achiasmy. Most lineages of the male Drosophila melanogaster flies are achiasmic, they are unaware of the recombination on all chromosomes while females show recombination process.