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Sex chromosomes (also referred to as allosomes, heterotypical chromosome, gonosomes, heterochromosomes, [1][2] or idiochromosomes[1]) are chromosomes that carry the genes that determine the sex of an individual. The human sex chromosomes are a typical pair of mammal allosomes. They differ from autosomes in form, size, and behavior.
There are two kinds of sex chromosomes–X and Y. In humans and in almost all other mammals, females carry two X chromosomes, designated XX, and males carry one X and one Y, designated XY. [1] A human egg contains only one set of chromosomes (23) and is a haploid. Sperm also have only one set of 23 chromosomes and are therefore haploid.
The XY sex-determination system is a sex-determination system present in many mammals, including humans, some insects (Drosophila), some snakes, some fish (guppies), and some plants (Ginkgo tree). In this system, the sex of an individual usually is determined by a pair of sex chromosomes. Typically, females have two of the same kind of sex ...
In 2021, scientists reported sequencing a complete, female genome (i.e., without the Y chromosome). [4] [3] The human Y chromosome, consisting of 62,460,029 base pairs from a different cell line and found in all males, was sequenced completely in January 2022. [5] The current version of the standard reference genome is called GRCh38.p14 (July ...
However, when an extra DAX1 gene is placed on the X chromosome, the result is a female, despite the existence of SRY, since it overrides the effects of SRY. [11] Even when there are normal sex chromosomes in XX females, duplication or expression of SOX9 causes testes to develop.
Most mammals, including humans, have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development. In the absence of a Y chromosome, the fetus will undergo female development. This is because of the presence of the sex-determining region of the Y chromosome, also known as the SRY gene. [5]
Chromosomes in humans can be divided into two types: autosomes (body chromosome (s)) and allosome (sex chromosome (s)). Certain genetic traits are linked to a person's sex and are passed on through the sex chromosomes. The autosomes contain the rest of the genetic hereditary information. All act in the same way during cell division.
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. [1] [2] Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.