The Y chromosome carries about 78 genes. However, these are rare events because the presence of dominant genetic anomalies severely reduces reproductive opportunities. The X chromosome is significantly longer than the Y chromosome and contains hundreds more genes. Thus, males are considered heterogametic — they can produce two different types of gametes, depending on whether the sperm carries an X or a Y chromosome. Genes that are carried by either sex chromosome are said to be sex linked. When any cell in the body divides, except… Individuals having two X chromosomes XX are female; individuals having one X chromosome and one Y chromosome XY are male.
She passed on the harmful allele to one of her four sons and at least two of her five daughters. In some animals where the males are XY, gene expression on one of the X chromosomes in females is silenced through the formation of heterochromatin. The father's sperm contains about half X and half Y chromosomes. The X chromosome, being larger, carries many more genes than does the Y. The SRY gene which is on the Y chromosome is misplaced in this disorder, almost always onto an X chromosome. The Y chromosome carries about 78 genes. Most of the Y chromosome genes are involved with essential cell house-keeping activities and sperm production. See also X trisomy ; XYY-trisomy. Clearly, there are not only females who are XX and males who are XY, but rather, there is a range of chromosome complements, hormone balances, and phenotypic variations that determine sex. This is in contrast to the case in humans where the mere presence of one Y chromosome confers maleness, irrespective of the number of X chromosomes or the ratio between sex chromosomes and autosomes. How are the sex chromosomes present in a male bird represented? Polyploidy — The presence of more than two complete sets of chromosomes in a cell. Unlike the paired autosomes, in which each member normally carries alleles forms of the same genes, the paired sex chromosomes do not carry an identical complement of genetic information. However, the presence of distinct male plants and female plants is relatively rare and only six percent of angiosperms show this characteristic, which is called dioecy. During meiosis the male XY sex-chromosome pair separates and passes on an X or a Y to separate gametes; the result is that one-half of the gametes sperm that are formed contains the X chromosome and the other half contains the Y chromosome. National Library of Medicine Chromosomes are thread-like molecules that carry hereditary information for everything from height to eye color. The female has two X chromosomes, and all female egg cells normally carry a single X. Sex chromosome abnormalities Abnormalities in the sex chromosome combination can result in a variety of gender-specific conditions that are rarely lethal. This means that almost any gene on the X, even if it is recessive in the female, will be expressed in males. National Library of Medicine. If the sperm carries an X chromosome, it will combine with the egg's X chromosome to form a female zygote. The effects of genes carried only on the Y chromosome are, of course, expressed only in males. Only one of the Y chromosome genes, the SRY gene, is responsible for male anatomical traits. As a result of marrying into other European royal families, the princesses Alice and Beatrice spread hemophilia to Russia, Germany, and Spain. People with this disorder have male external genitalia. The reason for this is that, in each somatic cell of a normal female, one of the X chromosomes is randomly deactivated.
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