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What are sex chromosomes? Name the two types of sex chromosomes?

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Hint: A typical pair of mammalian allosomes, the human sex chromosomes, decide the sex of an individual produced through sexual reproduction. Each cell nucleus in human beings contains 23 chromosome sets, for a sum of 46 chromosomes.

Complete Answer:The first 22 pairs are known as autosomes. Autosomes are homologous chromosomes which are chromosomes that actually contain the same genes (DNA regions) along their chromosomal arms in the very same order. Allosomes composed of two X chromosomes in most females, and X and y chromosomes in most males, are considered the chromosomes of the $23^{rd}$ pair. The X chromosome is very often present in the ovum as the $23^{rd}$ chromosome, while in a sperm cell, maybe an X or a Y chromosome will be present. All diploid species with allosome - determined sex acquire from each one of their parents half of their allosomes. In mammalian species, females are XX, they can pass either one of their X's along, and they can pass either an X or a Y because the males are XY. In addition to a mammal to be female, both parents must receive an X chromosome, while the person must receive an X chromosome from their mother but a Y chromosome from their father to be male. However during meiosis, these two chromosomes pair with each other, there is generally very limited homology or conjugation between them, primarily due to a large variation in their genetic content and size. One chromosome is often smaller, only certain genes that are essential for sex determination seem to have been retained.

Additional Information:
Often in female embryonic development, one of the X chromosomes is spontaneously and permanently partly deactivated in cells apart from egg cells: in certain cells, the X chromosome comes from the mother is deactivated, while in others, the father's X chromosome is disabled. For everybody’s cell, this assures that both sexes really have essentially one functioning copy of the X chromosome. The X chromosome is usually longer and contains hundreds of more genes than that of the Y chromosome. The X genes are predominant because the extra genes in the X chromosome have no counterpart in the Y chromosome. This means that in males, mostly every gene on the X will be expressed, even if it is recessive in the female. These are recognized as genes that are X-linked. Genes present only on the Y chromosome are related to and expressed mainly in males as Y-linked genes. The Y chromosome includes only 26 genes, in comparison to the large X chromosome. For cell maintenance, sixteen of such genes are responsible. Nine are involved in the production of sperm, and low sperm counts or infertility may occur if some are missing or defective. Male sexual features are responsible for one gene, named the SRY gene.

Note: Sex chromosome combination disorders can result in a range of occasionally dangerous gender-specific conditions. With a rate of approximately 1:400–500, these disorders are considered very common. Sex chromosome disorder-related genetic traits are less intense than autosomal anomalies and it is mostly due to inactivation of the X chromosome, and also the low gene content of Y chromosomes.