Sex determination in Humans Vs Birds

Mechanism of sex determination in humans

Sex determination refers to biologically determining the sex of the organism; where genetic composition indicate whether individual organisms are female or male which can result in sex differentiationLet’s throw some light on the mechanism of sex determination in humans and birds.

Mechanism of Sex Determination in Humans

Humans particularly have a sex determination of XY type. In this case, males produce two different types of gametes, 50% with X-chromosome and 50% with Y-chromosome i.e. males are heterozygous. Such a type of sex determination mechanism is an example of male heterogamety. This mechanism of sex determination is also seen in a few insects and mammals.

Mechanism of sex determination in humans

Image Source: NCERT

As we all know, humans have 23 pairs of chromosomes in each cell, out of which 22 pairs are the same in both males and females called autosomes. A pair of X-chromosomes are present in the female, whereas the X chromosome and Y chromosome are present in a male. Y chromosome which can be referred to as the counterpart of the X chromosome is comparatively smaller. It is interesting to note that during the process of sperm production (spermatogenesis) in males, two types of gametes are produced. Females particularly produce only one type of ovum with an X-chromosome.

There is an equal probability of fertilization of the ovum with the sperm carrying either the X or Y chromosome. In case the ovum fertilizes with a sperm carrying X-chromosome the zygote develops into a female (XX) and the fertilization of the ovum with the Y-chromosome carrying sperm results in male offspring. Thus, the genetic makeup of the sperm has a role in determining the sex of the child.

Mechanism of Sex Determination in Birds

In birds, both males and females have the same number of chromosomes. Females particularly produce two different types of gametes in terms of the sex chromosomes i.e. females are heterozygous. Such a mechanism of sex determination is an example of female heterogamety.

The two different sex chromosomes of a female bird are named Z and W chromosomes. Males have a pair of Z-chromosomes besides the autosomes.

What is the importance of sex determination?

Sex determination is useful in increasing the progeny of the desired sex which may be helpful for increased food supply as in the case of birds. It may help in avoiding sex-linked inheritable diseases. 

mechanism of sex determination Birds

Image Source: NCERT

Hope the article could explain to you the mechanism of sex determination in humans and birds.

Thank you for reading at MBD!

Team MBD

12th Biology students here is something more for you from chapter ‘Principles of Inheritance and variation’- Genetics Archives – My Biology Dictionary

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