Human Y chromosome | |
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Human Y chromosome (after G-banding)
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Y chromosome in human male karyogram
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Features | |
Length (bp) | 57,227,415 bp (GRCh38) |
No. of genes | 63 (CCDS) |
Type | Allosome |
Centromere position |
Acrocentric (10.4 Mbp) |
External map viewers | |
Ensembl | Chromosome Y |
Entrez | Chromosome Y |
NCBI | Chromosome Y |
UCSC | Chromosome Y |
Full DNA sequences | |
RefSeq | NC_000024 (FASTA) |
GenBank | CM000686 (FASTA) |
The Y chromosome is one of two sex chromosomes (allosomes) in mammals, including humans, and many other animals. The other is the X chromosome. Y is the sex-determining chromosome in many species, since it is the presence or absence of Y that determines the male or female sex of offspring produced in sexual reproduction. In mammals, the Y chromosome contains the gene SRY, which triggers testis development. The DNA in the human Y chromosome is composed of about 59 million base pairs. The Y chromosome is passed only from father to son. With a 30% difference between humans and chimpanzees, the Y chromosome is one of the fastest-evolving parts of the human genome. To date, over 200 Y-linked genes have been identified. All Y-linked genes are expressed and (apart from duplicated genes) hemizygous (present on only one chromosome) except in the cases of aneuploidy such as XYY syndrome or XXYY syndrome. (See Y linkage.)
The Y chromosome was identified as a sex-determining chromosome by Nettie Stevens at Bryn Mawr College in 1905 during a study of the mealworm Tenebrio molitor. Edmund Beecher Wilson independently discovered the same mechanisms the same year. Stevens proposed that chromosomes always existed in pairs and that the Y chromosome was the pair of the X chromosome discovered in 1890 by Hermann Henking. She realized that the previous idea of Clarence Erwin McClung, that the X chromosome determines sex, was wrong and that sex determination is, in fact, due to the presence or absence of the Y chromosome. Stevens named the chromosome "Y" simply to follow on from Henking's "X" alphabetically.