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Offspring have two sex chromosomes: an offspring with two X chromosomes (XX) will develop female characteristics, and an offspring with an X and a Y chromosome (XY) will develop male characteristics, except in various exceptions such as individuals with Swyer syndrome, that have XY chromosomes and a female phenotype, and de la Chapelle Syndrome ...
No genes are shared between the avian ZW and mammal XY chromosomes [26] and the chicken Z chromosome is similar to the human autosomal chromosome 9, rather than X or Y. This suggests not that the ZW and XY sex-determination systems share an origin but that the sex chromosomes are derived from autosomal chromosomes of the common ancestor of ...
Females therefore have 23 homologous chromosome pairs, while males have 22. The X and Y chromosomes have small regions of homology called pseudoautosomal regions. An X chromosome is always present as the 23rd chromosome in the ovum, while either an X or Y chromosome may be present in an individual sperm. [4]
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.
The Y chromosome is one of two sex chromosomes in therian mammals and other organisms.Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining chromosome because the presence of the Y chromosome causes offspring produced in sexual reproduction to be of male sex.
The ability for mammals to tolerate aneuploidies in the sex chromosomes arises from the ability to inactivate them, which is required in normal females to compensate for having two copies of the chromosome. Not all genes on the X chromosome are inactivated, which is why there is a phenotypic effect seen in individuals with extra X chromosomes.
Differences in basic number of chromosomes. These differences could have resulted from successive unequal translocations which removed all the essential genetic material from a chromosome, permitting its loss without penalty to the organism (the dislocation hypothesis) or through fusion. Humans have one pair fewer chromosomes than the great apes.
Phenotypic differences between sexes are evident even in cultured cells from tissues. [132] For example, female muscle-derived stem cells have a better muscle regeneration efficiency than male ones. [133] There are reports of several metabolic differences between male and female cells [134] and they also respond to stress differently. [135]