Y-chromosome

The two major types of genotypic sex determination, the mammalian and the avian types, can be referred to as XX/XY or ZZ/ZW, respectively. In animals expressing the XX/XY system, the male is the heterogametic sex (XY) while the female is homogametic (XX). The avian equivalent to the Y-chromosome of mammals is designated by the letter W, and the X-chromosome denoted by the... 

Tishler, P. V. Lamborot-Manzur, M. and Atkins, L. "Polymorphism of the Human Y Chromosome Fluorescence Microscopic Studies on the Sites of Morphological Variation". 

Chromosomal aberrations Gene mutation Dominant lethal mutation Micronucleus formation Micronucleus formation Micronucleus formation Chromosomal aberrations Sister chromatid exchange Micronucleus formation Chromosomal aberrations Sister chromatid exchange DNA-protein cross-links Nondisjunction of Y chromosome in sperm DNA damage (single-strand breaks)... 

On replication, insertion or deletion of bases may occur. Chain scission and chromosome breaks are also possible. Quinacrine is useful in human cytogenetics, since it intercalates significantly into the heterochromatin of the Y chromosome, making it fluoresce and rendering it identifiable cytologically. Detection of the Y chromosome is important in prenatal sex determination. Other dyes present in our environment are potentially mutagenic. For example, some hair dyes were shown to be mutagenic for E. coli. 

Hammer MF, Karapet T, Rasanayagam A, Wood ET, Althiede TK, Jenkins T et al. Out of Africa and back again Nested cladistic analysis of human Y chromosome variation. Mol Biol Evol 1998 15 427-441. 

Autosome A chromosome not involved in sex determination. The diploid human genome consists of 46 chromosomes, 22 pairs of autosomes, and one pair of sex chromosomes (X and Y chromosomes). 

Xia X, Rasmussen T, Alvarez X, et al. Fluorescence in situ hybridization using an old world monkey Y chromosome-specific probe combined with immunofluorescence staining on rhesus monkey tissues./. Histochem. Cytochem. 2007 55 1115-1121. 

Detection of chromosome fragments. Individuals with Turner s syndrome are, in some cases, mosaic for a portion of or for the entire Y chromosome (46,XY/45,X). Since such individuals may be at increased risk for gonadal tumors, Southern blot or PCR analysis has been used to detect the presence of Y chromosome segments in studies of DNA from peripheral blood samples. Similarly, the fetal sex as well as the presence of some aneuploid states (e.g., trisomy 18) can be determined by analysis of DNA from chorionic villi or amniotic fluid cells. 

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females. Females have two copies of the X chromosome, while males have one X and one Y chromosome. 

X-linked dominant inheritance The chance of passing on an X-linked dominant condition differs between men and women because men have one X chromosome and one Y chromosome, while women have two X chromosomes. A man passes on his Y chromosome to all of his sons and his X chromosome to all of his daughters. Therefore, the sons of a man with an X-linked dominant disorder will not be affected, but all of his daughters will inherit the condition. A woman passes on one or the other of her X chromosomes to each child. Therefore, a woman with an X-linked dominant disorder has a 50 percent chance of having an affected daughter or son with each pregnancy. 

In addition to the 22 pairs, a female cell contains two X chromosomes and a male cell contains an X and a Y chromosome. When a female egg (carrying an X chromosome) combines with male sperm having an X chromosome, a female offspring is born. When the egg combines with a sperm having a Y chromosome, a male offspring results. 

Normal males inherit an X chromosome from their mother and a Y chromosome from then-father, whereas normal females inherit an X chromosome from each parent. Because the Y chromosome carries only about 30 protein-coding genes and the X chromosome carries hundreds of protein-coding genes, a mechanism must exist to equalize the amount of protein encoded by X chromosomes in males and females. This mechanism, termed X inactivation, ocairs very early in the development of female embryos. When an X chromosome is inactivated, its DNA is not transcribed into mRNA, and it is visuahzed under the microscope as a highly condensed Barr body in the nuclei of interphase cells. X inactivation has several important characteristics It is random—in some cells of the female embryo, the X chromosome inherited from the father is inactivated, and in others the X chromosome inherited from the mother is inactivated. Like coin tossing, this is a random process. 

Klinefelter syndrome (47,XXY) is seen in approximately 1 in 1,000 males (all individuals with this condition have a male phenotype because they have a Y chromosome). Klinefelter males are nearly always sterile because of atrophy of the seminiferous tubules. They tend to be taller than average, with abnormally long arms and legs. Breast development (gynecomastia) is seen in about one third of cases, and the IQ is on average 10-15 points below that of unaffected siblings. Individuals have also been seen with 48.XXXY and 49,XXXXY karyotypes the additional X chromosomes produce a more severely affected phenotype. 

A. Normal crossover between the pseudoautosomal regions of X and Y produces a Y chromosome that retains the SRY gene. 

In the particular case of geographical spreading of single locus mutations on mitochondrial DNA or on Y chromosome [22, 23], we consider a growing population that diffuses slowly in time and assume that the net rate of growth is a linear function of population density, p(n) = — njrioo), where is... 

To further confirm the data, we performed Y chromosome PCR. The sensitivity of this method was 10 or 1000 cells detected in a total of 10 cells that were screened. Organs of female rats infused with male MSC were harvested at 24 hand at day 3 after infusion. Real-time quantitative PCR withY chromosome-specific primers showed amplification only in the lungs at 24 h after cell infusion (Figure 5), whereas kidney, liver, spleen, and bone marrow were negative, thereby further corroborating our results about a clearance of MSC from kidneys long-term. 

Figure 5. Detection of male MSC by Y-PCR. Y chromosome PCR at 24 h after MSC infusion from a male donor into female recipients with AKl. The only organ positive for Y chromosome DNA was the lung (lane 2). Kidney cortex and medulla as well as liver and spleen from 2 animals were negative (lanes 3-11). Lane designation A-female DNA B-male DNA 2 lung 3-kidney cortex 4-kidney medulla 5-liver 6-spleen 7-wound scar 8-lung 9-bone marrow 10-liver 11-spleen.

All nucleated cells except eggs and sperm (gametes) carry two sets of genetic material in their nuclei, one from the individual s mother and one from the father, hi human cells there are 22 pairs of homologous chromosomes plus an X chromosome and a Y chromosome. In the formation of gametes, this must be reduced to a single set, that is, the diploid number of chromosomes (46) must be reduced to the haploid number (23). 

The human genome contains approximately 100000 genes which are distributed with a total DNA sequence of 3 billion nucleotides. The DNA of the human genome is divided into 24 exceptionally large molecules each of which is a constituent of a particular chromosome, of which 22 are autosomes and two are sex chromosomes (X and Y chromosomes). 

Odor types distinctive of H2b and Hdh genotypes already appear in the urine of 1-day-old mouse pups (Yamazaki et ah, 1992a). At that age, the normal intestinal bacterial flora is not yet present and hence is not necessary for the odor (Yamazaki et ah, 1992b). In addition to MHC, gene(s) on the X and Y chromosomes and other autosomal genes contribute to individual odors (Yamazaki etal, 1986,1990). 

Yamazaki, K., Beauchamp, G. K., Matszaki, O., et al. (1986). Participation of the murine X and Y chromosomes in genetically determined chemosensory identity. Proceedings of the National Academy of Sciences, USA 83,4438-4440. 

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