Y chromosome, the smallest chromosome of the karyotpe, is one of the two sex chromosomes. In 1905, Nettie Stevens identified that Y chromosome is a sex-determining chromosome, while conducting one study of the mealworm Tenebrio molitor. He also proposed that chromosomes always existed in pairs. In 1890 Hermann Henking discovered that Y chromosome was the pair of the X chromosome. All chromosomes normally appear to take on a well defined shape during mitosis when seen under microscope. This shape is vaguely X-shaped for all chromosomes. Interestingly, the Y chromosome looks like the English alphabet Y during mitosis, due to merging of the two very short branches (Bainbridge, 2003). Every species organism consists of different set of chromosome with one set of sex determining chromosome.
The X and Y chromosomes are thought to have evolved from a pair of identical chromosomes, known as autosome. The mammalian males are heterogametic (produces X and Y chromosome bearing sperms in equal proportions), and the females are heterogametic (all female gametes are X bearing). It was found that Y chromosome has high repetitive DNA sequence content which consists of pseudogenes and does not have any function (Delbridge et al., 1999). In males, Y chromosome consists of SRY gene which triggers embryo development as male. Y chromosome is the smallest chromosome consists of 2-3% of haploid genome and contains between 70 and 200 genes (Quintana-Murci et al., 2001). Y chromosome consists of 2 arms- short arm (Yp) and long arm (Yq). These arms consist of 2 pseudoautosomal regions PAR1 and PAR2 which recombine with their homologous regions on X chromosome. The absence of recombination makes genetic mapping of the Y-specific region impossible, and the ...
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...requency in Human Y Chromosomal UTY Gene. OMICS A Journal of Integrative Biology Volume 15, Number 3, 2011
27. Greenfield, A., Carrel, L., Pennisi, D., Philippe, C., Quaderi, N., Siggers, P., et al.. (1998). The UTX gene escapes X inactivation in mice and humans. Hum Mol Genet 7, 737–742.
28. SATORU TOYOSAWA, COLM O’HUIGIN, FELIPE FIGUEROA, HERBERT TICHY, AND JAN KLEIN. Identification and characterization of amelogenin genes in monotremes, reptiles, and amphibians. Proc. Natl. Acad. Sci. USA Vol. 95, pp. 13056–13061, October 1998
29. Anette Mayer, Georgia Lahr, Dick F. Swaab, Christof Pilgrim, Ingrid Reisert. The Y-chromosomal genes SRY and ZFY are transcribed in adult human brain. Neurogenetics (1998) 1 :281–288
30. Koopman P, Gubbay J, Vivian N, Goodfellow P, Lovell-Badge R. Male development of chromosomally female mice transgenic for Sry. Nature. 1991;351:117–121
However, in a person with PWS, the 15th chromosome has been given 2 genes from the mother, and none from the father. This is called maternal UPD ( uni-parent disomy) in which 2 copies of the maternal chromosome are inherited with no paternal contribution. Despite the presence of 2 intact chromosomes, there is a functional abnormality in the imprinting that may lead to the absence of gene expression from the paternally donated chromosome, resulting in the PWS phenotype (physical trait) that is common in persons with PWS.
-Reilly Philip. Is It In Your Genes. Cold Spring Harbor Laboratory Press. 2004: 223-228. Print
The size of the terminal deletion may vary from a subtle 1.4Mb to a classic 30Mb [5]. Earlier genotype-phenotype correlation studies reveal that the main characteristic feature of WHS - the ‘Greek warrior helmet face’, is caused due to the hemizygosity of the WHSC1 gene located in the WHS critical region (WHSCR).[5] Various other genes are also located in the WHSCR which are responsible for most other phenotypic features. More precisely, the Wolf-Hirschhorn syndrome critical region (WHSCR) is located at 4p16.3 region. Approximately 25% of the patients with WHS deletion in this region are not detectable by cytogenetic karyotyping [6]. Hence, FISH has to be performed.
Turner’s syndrome is a genetic conditions that affects the female’s sex chromosome. In (http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001417/) Turner’s syndrome occurs when cells are missing all or part of an X chromosome. It’s common of the female patient to only have one X chromosome. Although, some individuals may have two X chromosomes but one is defective. It is thought that an estimated 1 out of 2000-2500 females suffer from this genetic condition worldwide but it’s usually females with this condition don’t survive their birth. Due to this abnormality, the genes that is defective “affect the growth and sexual development of the female” (http://learn.genetics.utah.edu/content/disorders/whataregd/turner/). However other disabilities and delays do occur even though these traits can vary case by case.
these are egg cells and sperms, each with a reduced or halved number of. chromosomes. The chromosomes are. The number of chromosomes is restored when two gametes fuse together to form a zygote. A cell with two copies of each. chromosome is called a diploid cell and a cell with one copy of each.
Jacob Syndrome is a rare condition where males contain an additional copy of the Y chromosome in their cells. According to the Genetic and Rare Diseases Information Center, (GARD, 2012), other names for Jacob Syndrome include: 47, XYY syndrome, XYY Karyotype, and YY syndrome. Statistics from Genetics Home Reference (2014) state that Jacob Syndrome appears in approximately 1 in 1,000 male newborns. In the United States, 5 to 10 male newborns have Jacob Syndrome.
The most common way of getting Angelman syndrome is through chromosome deletion. This is responsible for about 68% of all cases o...
Lewis, Ricki, (2014), Human Genetics, 11th Edition, Chapter 12. Gene Mutation. [VitalSource Bookshelf Online]. Retrieved from
By utilizing, and, if possible, modifying this special DNA structure, one may see a reduction of age related illness, diseases, and signs of aging. In this review of human telomeres, we will discuss the roles and functions of the telomere, its structure, and the relation of telomere length to aging and tumorigenesis. Role and Functions of The Telomeres Telomeres are special DNA structures that consist of repetitive nucleotide sequences, which serve as a “cap” to protect the ends of the chromosomes. These repetitive sequences can range from thousands of base pairs in Vertebrates to about a few hundreds of base pairs in yeast cells (Oeseburg, et al. 2009). The 'Secondary' of the 'Secondary' of the 'Secondary' of the 'Secondary' of the 'Secondary' of the 'Secondary' of the 'Secondary' of the 'Secondary' of the 'Secondary' of the 'S Located at the ends of the chromosomes, the telomeres serve as a biological life line for cells.
middle of paper ... ... World Book Inc, 2000. Davis, Lloyd S. and John T Darby. Penguin Biology. San Diego: Academic Press, Inc., 1990.
Gender is determined by the sex chromosomes, XX produces a female, and XY produces a male. Males are produced by the action of the SRY gene on the Y chromosome, which contains the code necessary to cause the indifferent gonads to develop as testes (1). In turn the testes secrete two kinds of hormones, the anti-Mullerian hormone and testosterone, which instruct the body to develop in a masculine fashion (1). The presence of androgens during the development of the embryo results in a male while their absence results by default in a female. Hence the dictum "Nature's impulse is to create a female" (1). The genetic sex (whether the individual is XX or XY) determines the gonadal sex (whether there are ovaries or testis), which through hormonal secretions determines the phenotypic sex. Sexual differentiation is not drive...
During prophase I, homologous chromosomes pair and form snynapses. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. The bivalent has two chromosomes and four chromatids, with one chromosome coming from each parent.
Typically males have XY chromosomes, and women have XX chromosomes; however, hermaphrodites are neither male nor female. One reason comes from Turner's Disease where the chromosomes are XO, and there is a sex chromosome missing. Another mutation is the XXY chromosomes, known as Klinefelter's Disease, which occurs in an average of one out of every 1000 births. There is also, Mosaicism, where different cells split into different parts, making up XY and XO chromosomes. Hormonal complications can change the gender...
Typically, XX chromosomes designate females and XY designate males, which both of these will develop into socially acceptable genders of the assigned chromosomes. Although this is mostly correct, there are some variations to the rule in which a person will differ from the assigned chromosomes and have physiological differences that will affect gender identity development. Eliza Dragowski, an assistant professor psychology, writes in a report titled Childhood Gender Identity… Disorder? Developmental, Cultural, and Diagnostic Concerns, "The second path points to anatomical brain differences. It is supported by postmortem examinations of brains of male-to-female transsexuals, which show a typical female-sized portion of the central subdivision of the bed nucleus of the stria terminal, a brain area vital in sexual behavior." This proves brain similarities between males and females, which can lead to them becoming transsexuals later in life. Their brain affects how they develop their own gender identity. Furthermore, genetic differences influence a developing identity, "review of the most recent research indicates the presence of various genetic variations that do not cause changes in reproductive anatomical structures but may produce gender-variant identities” (Dragowski). A variation of these genes will have a significant effect on gender since its part of their
The X-chromosome is one of the two sex chromosomes(the other being Y) that is responsible for a variety of factors in a child’s developmental growth, the most commonly known being their biological sex. Researchers at the National Center for Biotechnology Information have studied the X-chromosome and its relation to homosexuality in men. Preceding their studies, the researchers hypothesized, “If the X Chromosome contains a gene that increases the probability of an individual’s being homosexual, then genetically related gay men should share X chromosome markers close to that gene. If no such gene exists, then no statistically significant correlations between sexual orientation and X chromosome will be observed” (Bocklandt, Horvath, Vilain, Hamer).