Name: Sex linked Inheritance
Uploaded: 2019-07-19
Duration: 3 min 21 s
Description: Sex linkage describes the sex-specific patterns of inheritance and presentation when a gene mutation is present on a sex chromosome rather than a non-sex chr...

Question

Describe the chromosomal basis of sex determination in humans, honeybees and birds.

Accepted Answer

Sex determination is the establishment of sex through differential development in an organism or offspring. It determines whether it will be male or female. Sex of human being and insects like grasshopper, Firefly, Drosophila etc. is determined genetically. Some organisms like turtles rely entirely on environmental factors such as temperature for sex determination. It can be done by finding the number of chromosomes or type of chromosomes present in the organisms. The organisms which contain complete sets of chromosomes are diploid while the haploid organisms contain half the number of chromosomes.

Chromosomal basis of sex determination in humans:

In humans, the male-specific Y chromosome plays a pivotal role in sex determination, and also bears genes that are required for spermatogenesis. However, not all the genes that are needed to make a testis or to make germ cells need to be on the Y chromosome, and many are known to be located on the X chromosome or on the autosome. Human females have two X chromosomes (XX) and males have a single X and a single Y chromosome (XY).

Chromosomal basis of sex determination in Honeybees:

The sex determination in the honey bees is mainly understood by the fertilization and non-fertilization of eggs. An offspring formed of the union of a sperm and an egg develops as a female (queen or worker), and an unfertilized egg develops as a male (drone) by means of parthenogenesis. It is called Haplo-diploid system.

Chromosomal basis of sex determination in Birds:

The ZZ and ZW type of sex determination occurs in the birds in which females are heterozygous (ZW) and males are homozygous (ZZ). The sex chromosomes in birds are designated Z and W, and the male is the homomorphic sex (ZZ) while the female is heteromorphic (ZW).

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