Y linkage, also known as holandric inheritance (from

Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

ὅλος ''hólos'', "whole" + ἀνδρός ''andrós'', "male"), describes traits that are produced by genes located on the

Y chromosome The Y chromosome is one of two sex chromosomes (allosomes) in therian mammals, including humans, and many other animals. The other is the X chromosome. Y is normally the sex-determining chromosome in many species, since it is the presence or abs ...

. It is a form of sex linkage. Y linkage can be difficult to detect. This is partly because the Y chromosome is small and contains fewer genes than the

autosomal chromosomes An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosomes ...

or the

X chromosome The X chromosome is one of the two sex-determining chromosomes (allosomes) in many organisms, including mammals (the other is the Y chromosome), and is found in both males and females. It is a part of the XY sex-determination system and XO sex ...

. It is estimated to contain about 200 genes. Earlier, the human Y chromosome was thought to have little importance;. Although the Y-chromosome is sex-determining in humans and some other species, not all genes that play a role in sex determination are Y-linked. The Y-chromosome, generally does not undergo

genetic recombination Genetic recombination (also known as genetic reshuffling) is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. In eukaryo ...

and only small regions called pseudoautosomal regions exhibit recombination. The majority of the Y-chromosome genes that do not recombine are located in the "non-recombining region". For a trait to be considered Y linkage, it must exhibit these characteristics: * occurs only in males * appears in all sons of males who exhibit that trait * is absent from daughters of trait carriers; instead the daughters that are

phenotypically In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...

normal and do not have affected offspring. These requirements were established by the pioneer of Y linkage, Curt Stern. Stern detailed in his paper genes he suspected to be Y-linked. His requirements at first made Y linkage hard to prove. In the 1950s using human pedigrees, many genes were incorrectly determined to be Y-linked. Later research adopted more advanced techniques and more sophisticated statistical analysis. Hairy ears are an example of a gene once thought to be Y-linked in humans; however, that hypothesis was discredited. Due to advancements in

DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. T ...

, Y linkage is getting easier to determine and prove. The Y-chromosome is almost entirely mapped, revealing many Y-linked traits. Y linkage is similar to, but different from X linkage; although, both are forms of sex linkage. X linkage can be genetically linked and sex-linked, while Y linkage can only be genetically linked. This is because males' cells have only one copy of the Y-chromosome. X-chromosomes have two copies, one from each parent permitting recombination. The

contains more genes and is substantially larger. Some ostensibly Y-linked traits have not been confirmed. One example is hearing impairment. Hearing impairment was tracked in one specific family and through seven generations all males were affected by this trait. However, this trait occurs rarely and has not been entirely resolved. Y-chromosome deletions are a frequent genetic cause of

male infertility Male infertility refers to a sexually mature male's inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen ...

Animals

Guppies

In guppies, Y-linked genes help determine sex selection. This is done indirectly by traits that allow the guppy to appear more attractive to a prospective mate. These traits were shown to be on the Y-chromosome and thus Y-linked. Also in guppies, it appears that the four measures of sexual activity is Y-linked.

Rats

Hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high b ...

, or high blood pressure, appears to be Y-linked in the hypertensive rat. One loci was autosomal. However, the second component appeared to be Y-linked. This held through the third generation of rats. Male offspring with a hypertensive father had significantly higher blood pressure than male offspring with a hypertensive mother indicating that a component of the trait was Y-linked. The results were not the same in females as in males, further hinting at a Y-component.

Hairy ears

Hairy ears were thought to be a Y-linked trait, but this was disproven.

Genes known to be contained on the human Y chromosome

In general, traits that exist on the Y chromosome are Y-linked because they only occur on that chromosome and do not change in recombination. As of 2000, a number of genes were known to be Y-linked, including:{{cite web, url=http://www.medterms.com/script/main/art.asp?articlekey=15745 , title=Y-linked gene definition - Medical Dictionary: Definitions of Popular Terms Defined on MedTerms , publisher=Medterms.com , date=2012-09-20 , access-date=2014-06-29 * ASMTY (acetylserotonin methyltransferase), * TSPY (testis-specific protein), * IL3RAY (interleukin-3 receptor), * SRY (sex-determining region), * ZFY (zinc finger protein), * PRKY (protein kinase, Y-linked), * AMGL (amelogenin), * ANT3Y (adenine nucleotide translocator-3 on the Y), * AZF2 (azoospermia factor 2), * BPY2 (basic protein on the Y chromosome), * AZF1 (azoospermia factor 1), * DAZ (Spermatogenes is deleted in azoospermia), * RBM1 (RNA binding motif protein, Y chromosome, family 1, member A1), * RBM2 (RNA binding motif protein 2), and * UTY (ubiquitously transcribed TPR gene on Y chromosome). *

USP9Y Ubiquitin specific peptidase 9, Y-linked (fat facets-like, Drosophila), also known as USP9Y, is an enzyme which in humans is encoded by the ''USP9Y'' gene. It is required for sperm production. This enzyme is a member of the peptidase C19 family an ...

AMELY Amely was an American rock band from Orlando, Florida, United States, formed in 2008. The band comprised four members; Petie Pizarro (Vocals/Guitar), Brandon Walden (Guitar), Patrick Ridgen (Bass) and Nate Parsell (Drums). The sound of the band ...

References

External links

Y-linked Genetic Diseases at wrongdiagnosis.com
* http://learn.genetics.utah.edu/content/pigeons/sexlinkage/ * http://www.livestrong.com/article/74388-y-linked-genetic-diseases/ * http://www.medicinenet.com/script/main/art.asp?articlekey=15729 * https://www.ncbi.nlm.nih.gov/books/NBK22266/#A296 * http://learn.genetics.utah.edu/content/pigeons/geneticlinkage/ ± Genetics Classical genetics