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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]
In humans and many other species of animals, the father determines the sex of the child. 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.
The X and Y sex chromosomes are different in shape and size from each other, unlike the rest of the chromosomes , and are sometimes called allosomes. In some species, such as humans, organisms remain sex indifferent for a time during development ( embryogenesis ); in others, however, such as fruit flies, sexual differentiation occurs as soon as ...
The X-chromosome carries a larger number of genes in comparison to the Y-chromosome. In humans, X-chromosome inactivation enables males and females to have an equal expression of the genes on the X-chromosome since females have two X-chromosomes while males have a single X and a Y chromosome. X-chromosome inactivation is random in the somatic ...
Sex linked diseases are passed down through families through one of the X or Y chromosomes. Since usually men inherit Y chromosomes, they are the only ones to inherit Y-linked traits. Men and women can get the X-linked ones since both inherit X chromosomes. [22] An allele is either said to be dominant or recessive. Dominant inheritance occurs ...
XX male syndrome, also known as de la Chapelle syndrome, is a rare intersex condition in which an individual with a 46,XX karyotype develops a male phenotype. [2] Synonyms for XX male syndrome include 46,XX testicular difference of sex development (or 46,XX DSD) [3] [4] [5] [6]
The list of organisms by chromosome count describes ploidy or numbers of chromosomes in the cells of various plants, animals, protists, and other living organisms. This number, along with the visual appearance of the chromosome, is known as the karyotype , [ 1 ] [ 2 ] [ 3 ] and can be found by looking at the chromosomes through a microscope .
[14] [15] These genes contain an average of 10 introns and the average size of an intron is about 6 kb (6,000 bp). [16] This means that the average size of a protein-coding gene is about 62 kb and these genes take up about 40% of the genome. [17] Exon sequences consist of coding DNA and untranslated regions (UTRs) at either end of the mature mRNA.