Sex Determination in Humans MCQ - NEET Practice Questions & Answers

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Sex Determination, Sex Determination: XX Female & XY Male Type is considered one of the most asked concept.
28 Questions around this concept.

Sex Determination

The initial clue about the genetic/chromosomal mechanism of sex determination can be traced back to some of the experiments carried out in insects.
The cytological observations made in a number of insects led to the development of the concept of genetic/chromosomal basis of sex-determination.
Henking (1891) could trace a specific nuclear structure all through spermatogenesis in a few insects, and it was also observed by him that 50% of the sperm received this structure after spermatogenesis, whereas the other 50% sperm did not receive it.
Henking gave a name to this structure as the X body but he could not explain its significance.
Further investigations by other scientists led to the conclusion that the ‘X body’ of Henking was in fact a chromosome and that is why it was given the name X-chromosome.
Due to the involvement of the X-chromosome in the determination of sex, it was designated to be the sex chromosome, and the rest of the chromosomes were named as autosomes.
When males carry different types of sex chromosomes, such that two different types of gametes are produced, the condition is said to be male heterogamety. For example, a human male has XY as sex-chromosomes. So, two types of sperm are produced, half carrying the X-chromosome and the other half carrying the Y-chromosome.
Similarly, when females carry different types of sex chromosomes and produce different types of gametes, it is called female heterogamety.

Sex Determination: XX Female & XY Male Type

In most insects (e.g., fruit fly) and mammals including humans, the female is homogametic (XX) and male is heterogametic (XY) consisting of two dissimilar chromosomes X and Y.
The females produce ova all of one type having X chromosome.
Males produce two types of sperm: -50% with X-chromosome and remaining 50% with Y-chromosome.
Thus, the sex chromosomes in female are homomorphic and those of male are heteromorphic.
In fertilisation, an ovum can only carry an X chromosome. It is therefore the sex chromosome found in the sperm – either X or Y – that determines whether a zygote will be female or male, respectively.