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In the XY sex-determination system, the female-provided ovum contributes an X chromosome and the male-provided sperm contributes either an X chromosome or a Y chromosome, resulting in female (XX) or male (XY) offspring, respectively. Hormone levels in the male parent affect the sex ratio of sperm in humans. [25]
[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 2023). It consists of 22 autosomes plus one copy of the X chromosome and one copy of the Y chromosome.
The human brain. Differences in male and female brain size are relative to body size. [83] Early research into the differences between male and female brains showed that male brains are, on average, larger than female brains. This research was frequently cited to support the assertion that women are less intelligent than men.
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] Thus, male mammals typically have an X and a Y chromosome (XY), while female mammals typically have two X chromosomes (XX).
It is caused by a change in a gene called FMR1. A small part of the gene code is repeated on a fragile area of the X chromosome. The more repeats, the more likely there is to be a problem. Males and females can both be affected, but because males have only one X chromosome, a single fragile X is likely to affect them more.
The human Y chromosome is composed of about 62 million base pairs of DNA, making it similar in size to chromosome 19 and represents almost 2% of the total DNA in a male cell. [ 54 ] [ 55 ] The human Y chromosome carries 693 genes , 107 of which are protein-coding . [ 56 ]
The ZW sex-determination system is reversed compared to the XY system: females have two different kinds of chromosomes (ZW), and males have two of the same kind of chromosomes (ZZ). In the chicken, this was found to be dependent on the expression of DMRT1. [ 24 ]
This is an accepted version of this page This is the latest accepted revision, reviewed on 23 December 2024. DNA molecule containing genetic material of a cell This article is about the DNA molecule. For the genetic algorithm, see Chromosome (genetic algorithm). Chromosome (10 7 - 10 10 bp) DNA Gene (10 3 - 10 6 bp) Function A chromosome and its packaged long strand of DNA unraveled. The DNA's ...