Sex Chromosome – geeksforjobs


Hey all, Welcome to Geeksforjobs

Sex chromosome


A specific pair of chromosomes is used to determine the sex of individuals in diploid organisms such as humans. It is different for each sex. These chromosomes are called allosomes, heterosomes, or sex chromosomes. Other types of chromosomes are called autosomes or autosomal chromosomes. These carry genes that control somatic symptoms and have no effect on the sex of the child. The sex chromosomes may or may not be the same size. But, each pair of homologous autosomes is similar in size.

Dissimilar sex chosmos

There are four types


Y -> small chromosome

X -> big chromosome

The females have a pair of X chromosomes or can be expressed as XX.

Males have both X and Y chromosomes or can be expressed as XY.


Such disparity is found in mammals, including humans and insects, including fireflies. The same sex chromosomes as women are called homomorphic and the desmiller sex chromosome of males is described as heterorphic. The genes, which affect sex, are contained in the X chromosome. The Y chromosome usually contains heterochromatin and has few or no genes. Although different in shape and size, the Y and X chromosomes act as chromosomes in meiosis; They pair, separate, and pass into different gametes. When X determines female sex, another determines female sex and is called endosome.

Gender determination


Organisms with homomorphic sex chromosomes (XX) produce only one type of gametes and are called homologous organisms. Organisms with heteromorphic sex chromosome (XY) produce two types of gametes and are called heterometric organisms. When the former example is a human woman, the latter example is a human woman.

Case of humans:

During spermatogenesis in human males, two types of gametes – X and Y – are produced. However, during egg production, only X is produced. So, there is a similar possibility of fertilization of X with sperm carrying either X or Y chromosome. If X in the egg is fertilized with X in sperm, the zygote develops into a female (XX) and when X in the egg is fertilized with Y, a male is formed (XY).


Here in males, the Y chromosome is missing and only one sex chromosome is present. The position in male is XO (O-> absence) and in females it is XX.

It is present in some roundworms and some insects such as cockroaches.


Males have a pair of Z chromosomes or can be expressed as ZZ and are thus homomorphic. Females have both Z and W chromosomes or can be expressed as ZW and thus are heterorphic.

It is present in many reptiles such as reptiles, fishes and birds.


In women here, the Z chromosome is missing and only one sex chromosome is present. The condition in women is ZO (O-> Absence) and in women it is ZZ.

It is present in butterflies and moths.

The conclusion

In short, sex chromosomes are unevenly coupled chromosomes that help determine the sex of an organism. It can be homomorphic or heteromorphic. When homomorphic organisms produce only one type of gametes aka homogeneous, heteromorphic organisms produce heterosexuals.

Leave a Comment

Your email address will not be published. Required fields are marked *