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Sex Determination in Humans - Practice Questions & MCQ
Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET
Quick Facts
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Sex Determination, Sex Determination: XX Female & XY Male Type is considered one of the most asked concept.
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24 Questions around this concept.
Solve by difficulty
Which one of the following conditions of the zygotic cell would lead to the birth of a normal human female child?
Concepts Covered - 2
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.
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