Question

Differentiate between ‘ZZ’ and ‘XY’ type of sex-determination mechanisms.

Answer 1

In the above mechanisms, there is an interchange of homogametic and heterogametic types of gametes between males and females. Here, the XY type is opposite to the ZZ type of sex determination mechanism.

Complete answer:
Sex-determination mechanisms are the mechanisms through which the sex of offspring is determined. There are various types of sex determination mechanisms like ZZ, XY, etc.
ZZ type of sex-determination: In this sex chromosomes (sex chromosomes are the chromosomes which will determine the sex of offspring) are Z and W. In ZZ type of sex determination the females are heterogametic (gamete contains two different types of sex chromosomes) and males are homogametic (gametes contain same 2 chromosomes). The females here produce two types of gametes that are (A+Z) and (A+W) here A stands for autosomes and ZW stands for sex chromosomes. The males here produce only one type of gamete that is (A+Z). If the zygote gets a Z chromosome from mother and Z chromosome from father then the offspring is a male child (ZZ). If the zygote gets the W chromosome from the mother and Z chromosome from the father then the offspring is a female child (ZW). This type of sex determination mechanism is found in fish, birds, etc.

XY type of sex-determination: In this sex chromosomes are X and Y. In XY type of sex determination the males are heterogametic and females are homogametic. The males here produce two types of gametes. The gamete either contains the X chromosome or Y chromosome. The females here produce a single type of gamete containing only X chromosome. If the zygote receives an X chromosome from the father and X chromosome from the mother then the offspring is a female child (XX). If the zygote receives the Y chromosome from the father and X chromosome from the mother then the offspring is a male child (XY). This type of sex determination mechanism is found in humans and drosophila.

Note: ZZ type of mechanism also has a chromosome W in it. From the name, it is interpreted that there are only two chromosomes Z and Z.