
	Where results make sense

Topic: Sex chromosome

	Chromosome - MSN Encarta
		This process ensures that each chromosome moves to its proper place during mitosis, when a cell divides to give rise to two cells, and during meiosis, the process of cell division that gives rise to eggs or sperm.
		In the cells of most organisms that reproduce sexually, chromosomes occur in pairs: One chromosome is inherited from the female parent, and one is inherited from the male parent.
		Both males and females inherit one sex chromosome from the mother (always an X chromosome) and one sex chromosome from the father (an X in female offspring and a Y in male offspring).
	encarta.msn.com /encnet/refpages/RefArticle.aspx?refid=761566230 (971 words)

	Y chromosome - Genetics Home Reference
		The sex chromosomes are one of the 23 pairs of human chromosomes.
		Genes on the Y chromosome are among the estimated 20,000 to 25,000 total genes in the human genome.
		Chromosomal conditions involving the sex chromosomes often affect sex determination (whether a person has the sexual characteristics of a male or a female), sexual development, and the ability to have children (fertility).
	ghr.nlm.nih.gov /chromosome=Y (781 words)

	genome.gov \| Chromosome Abnormalities Fact Sheet
		To help identify chromosomes, the pairs have been numbered from 1 to 22, with the 23rd pair labeled "X" and "Y." In addition, each chromosome arm is defined further by numbering the bands that appear after staining; the higher the number, the further that area is from the centromere.
		The first 22 pairs of chromosomes are called "autosomes" and the final pair is called the "sex chromosomes." The sex chromosomes an individual has determines that person's gender; females have two X chromosomes (XX), and males have an X and a Y chromosome (XY).
		Chromosome abnormalities can be inherited from a parent (such as a translocation) or be "de novo" (new to the individual).
	www.genome.gov /11508982 (1121 words)

	Sex-determination system - Wikipedia, the free encyclopedia
		In many cases, sex determination is genetic: males and females have different alleles or even different genes that specify their sexual morphology.
		In other cases, sex is determined by environmental variables (such as temperature) or social variables (the size of an organism relative to other members of its population).
		Chromosomes in the ZW region in birds are autosomal in mammals, and vice-versa; therefore, it is theorized that the ZW and XY couples come from different chromosomes of the common ancestor.
	en.wikipedia.org /wiki/Sex_chromosome (725 words)

	X chromosome - Genetics Home Reference
		Early in embryonic development in females, one of the two X chromosomes is randomly and permanently inactivated in somatic cells (cells other than egg and sperm cells).
		Genes on the X chromosome are among the estimated 20,000 to 25,000 total genes in the human genome.
		Some cells have the usual two sex chromosomes (either two X chromosomes or one X chromosome and one Y chromosome), and other cells have only one copy of the X chromosome.
	ghr.nlm.nih.gov /chromosome=X (952 words)

	Sex chromosome clue to autism - 09 September 2003 - New Scientist (Site not responding. Last check: 2007-10-13)
		A small group of genes on the X chromosome regulate the brain's "threat-detector" and might explain the high prevalence of autism among males, researchers have discovered.
		The X chromosome carries many genes that are vital for a wide range of physiological functions.
		Women have two X chromosomes while men have an X and a Y. Because almost all women have two copies of X chromosome genes, their cells turn off, or inactivate, one copy.
	www.newscientist.com /article.ns?id=dn4145 (505 words)

	Sex Linked Genes
		Sex determination in mammals and some insects, is determined by the presence of a special pair of chromosomes called sex chromosomes.
		The early embryological differentiation of males and females is apparently based on the presence or absence of the Y chromosome.
		The Y chromosome contributes to determination of the sex of the child.
	www.pc.vccs.edu /tureman-intro/biology/MendelianGenetics/sexlinked.htm (1079 words)

	Sex Chromosome Abnormalities Found Among
		The present chromosome investigation is part of a larger prospective study of environmental factors on pregnancy, birth, and the fetus [1-3].
		Follow-up studies of 203 unselected children with sex chromosome abnormalities in the United States, Scotland, Canada, and Denmark [4-6] have shown that children with sex chromosome abnormalities are at increased risk for deviations in mental development compared to sibs and children with normal chromosomes.
		Chromosome examination was made of 88% (34,910) of all 39,618 live- born children at the Maternity Hospital in Århus during a 13-year period from 1969 to 1974 (4 years, 5 months) and from 1980 to 1988 (8 years, 7 months).
	www.aaa.dk /TURNER/ENGELSK/incidence.htm (4044 words)

	Y chromosome - Wikipedia, the free encyclopedia
		Other organisms have mirror image sex chromosomes: the female is "XY" and the male is "XX", but by convention biologists call a "female Y" a W chromosome and the other a Z chromosome.
		The human Y chromosome is unable to recombine with the X chromosome, except for small pieces of pseudoautosomal regions at the telomeres (which comprise about 5% of the chromosome's length).
		When chromosome surveys were first done in the 1960s, it was reported that a higher than expected number of men in prisons were found to have an extra Y chromosome, so that for a while it was thought to predispose a boy to antisocial behavior (and was dubbed the "criminal karyotype").
	en.wikipedia.org /wiki/Y_chromosome (1746 words)

	“Sex Linkage” — What does it mean
		As noted in an earlier article, the term “sex linkage” by itself simply means that a particular characteristic is linked to the sex chromosome, or more specifically, the gene for that particular characteristic lies on the sex chromosome.
		Her second chromosome is usually represented by a dot or nothing at all.
		Sons receive one of the cocks chromosomes and the active sex chromosome of the mother: + + + d The result is a blue cock, since the dilute gene must be present
	www.angelfire.com /oh/raraavis/sexlinkmating.html (1299 words)

	Sex Tutorial Weblog: Home Page (Site not responding. Last check: 2007-10-13)
		Meiotic drive is an interesting case of chromosomes exploiting meiosis to violate the normal Mendelian transmission ratios, and when it happens with a sex chromosome, it has interesting consequences for all sorts of things, from sex ratios to population extinction.
		The Graves and Shetty paper is a comprehensive overview of the cytological and phylogenetic data on the history of sex chromosomes in tetrapod (non-fish) vertebrates.
		But you should get an understanding of some of the processes that should be common to the evolution of sex chromosomes in all (or most) taxa, such as dosage compensation, the restriction of genetic exchange (recombination) surrounding a sex-determining locus, and the subsequent degeneration of the heteromorphic sex chromosome.
	blogs.law.harvard.edu /sextutorial (3104 words)

	News in Science - The origin of sex chromosomes - 29/10/1999
		"By fossil digging on the sex chromosomes, we were able to reconstruct the four events that drove sex chromosomes into their distinctive X and Y forms, and to date when these events occurred during evolution," says Lahn.
		The X chromosome was found to have four groups of genes physically arranged as four consecutive blocks, like the layers of rock in geological strata.
		Recombination, which is the process of swapping bits of genetic material between a pair of chromosomes during the formation of eggs or sperm, is essential to maintaining genetic identity between X and Y. Without it, the two chromosomes would diverge into completely distinct forms.
	www.abc.net.au /science/news/stories/s63100.htm (772 words)

	Papaya Sex-Chromosome Study Provides New Glimpse of Evolution / January 23, 2004 / News from the USDA Agricultural ... (Site not responding. Last check: 2007-10-13)
		The same process is thought to have occurred in the human genome during the millions of years of human sex chromosome evolution.
		In papaya, studies of sex chromosomes may help scientists understand inheritance of traits responsible for the size, shape and quality of this popular tropical fruit.
		This papaya chromosome resembles a primitive version of the human Y chromosome--perhaps as it existed 240 to 320 million years ago.
	www.ars.usda.gov /is/pr/2004/040123.2.htm (328 words)

	Stanford Psychiatry Neuroimaging Laboratory: Sex Chromosome Abnormalities
		Sex chromosome abnormalities (SCA) describe those conditions in which there is some variation among the normal euploidic sex chromosomes in male or female individuals.
		These variations are most often caused by non-disjunction of the 23rd sex chromosome pair during meiosis.
		While SCA can include a variety of abnormalities of the sex chromosomes, by far the most commonly occurring SCA involve the deletion (45,X or partial X monosomy) or addition (47,XXY, 47,XYY, 47,XXX) of an X or Y chromosome.
	spnl.stanford.edu /disorders/sca.htm (191 words)

	Sex chromosome conditions - WrongDiagnosis.com
		Chromosome diseases are genetic diseases where a large part of the genetic code has been disrupted.
		Chromosomes are long sequences of DNA that contain hundreds or thousands of genes.
		Every person has 2 copies of each of the 23 chromosomes, called chromosomes 1..22 (or "autosomes") and the 23rd is the sex chromosome, which is either X and Y. Men are XY and women are XX in the 23rd chromosome pair.
	www.wrongdiagnosis.com /s/sex_chromosome_conditions/intro.htm (520 words)

	MedlinePlus Medical Encyclopedia: Chromosome
		Chromosomes are long pieces of DNA contained in the nucleus of cells.
		Mitochondria have their own DNA strand, sometimes called "the 47th chromosome." All of your genes are contained within these 46 nuclear chromosomes and 1 mitochondrial chromosome.
		Two of the chromosomes (the X and the Y chromosome) determine your gender and are called sex chromosomes:
	www.nlm.nih.gov /medlineplus/ency/article/002327.htm (355 words)

	Human Chromosomal Abnormalities: Sex Chromosome Abnormalities
		The majority of known types of chromosomal abnormalities involve sex chromosomes.
		The high frequency of people with sex chromosome aberrations is partly due to the fact that they are rarely lethal conditions.
		A single Y chromosome is sufficient to produce maleness while its absence is necessary for femaleness.
	anthro.palomar.edu /abnormal/abnormal_5.htm (1047 words)

	Lesson Twelve : Sex Determination, Chromosomes and Mosaicism
		For example, the sex of a honeybee is determined by whether the egg is fertilized or not.
		Most animals have a pair of sex chromosomes and, together or individually (depending on the taxa) these determine the sex of the developing embryo and thus the sex of the fully-grown individual.
		Both sex determination and X inactivation are very important events that occur in the development of the early embryo but affect each individual for the rest of his or her life.
	www.synapses.co.uk /genetics/sexone.html (3485 words)

	Discovery Channel :: News :: Study: Platypus Retains Bird Sex Link
		The different fluorescent colors enabled the researchers to both identify and track the chromosomes and their involvement in meiosis, which is the process of cellular division that produces eggs in females and sperm in males.
		The overall system is described as XX/XY, with the resulting sex of the mating determined by a gene on the male Y chromosome.
		They embody a unified mixture of mammal, reptile, and bird physiology, with their sex chromosomes hearkening back to very early days of life when perhaps all sex chromosomes and sex determining genes evolved from a common ancestor.
	dsc.discovery.com /news/briefs/20041025/platypus.html (729 words)

	Sex Chromosome Variations - About 47XXY (Site not responding. Last check: 2007-10-13)
		Harry Klinefelter accurately described this condition in 1942, it was not until 1956 that other researchers reported that many boys with this description had 47 chromosomes in each cell of their bodies instead of the usual number of 46.
		All men have one X chromosome and one Y chromosome, but sometimes a variation will result in a male with an extra X. This is Klinefelter Syndrome and is often written as 47,XXY.
		The testes produce the major male sex hormone testosterone and the amount of this hormone may be decreased in boys with Klinefelter Syndrome.
	www.malattiemetaboliche.it /articoli/sex_chromosome.htm (833 words)

	Sex-determining genes of infectious fungus resemble human Y chromosome
		Regions of the genome that determine the sexual identity of the infectious fungus Cryptococcus neoformans bear striking similarities to the human Y chromosome -- the sex chromosome associated with male characteristics -- the team found.
		Sexual identity is governed by sex chromosomes in plants and animals.
		The human Y chromosome is also barred from recombination along most of its length, a necessary requirement to prevent genes that encode male traits from infiltrating the female X chromosome, Heitman noted.
	www.eurekalert.org /pub_releases/2004-11/dumc-sgo111004.php (751 words)

	Brain & Nervous System > Sex Chromosome Genes Influence Aggression and Maternal Behavior
		"Sex chromosome genes may not be the whole story that determines how aggressive or motherly we are, but they are a part of it."
		In their experiments, the researchers compared mice with or without the Sry gene (either males with testes or ovary-bearing females) to mice with the XX versus XY sex chromosomes.
		The researchers found that the sex chromosome complement, as well as gonadal sex differences, influences behavior.
	www.emaxhealth.com /85/4726.html (375 words)

	ScienceDaily: Sex Chromosome Genes Influence Aggression And Maternal Behavior, Say Researchers (Site not responding. Last check: 2007-10-13)
		“The differences in sex chromosomes, XX versus XY, are also responsible for differences in adult behavior,” explained Emilie Rissman, PhD, a professor of biochemistry and molecular genetics at UVa, who studied aggression and maternal behavior in genetically engineered mice.
		Sex linkage -- Sex linkage is the phenotypic expression of an allele that is dependent on the gender of the individual and is directly tied to the sex chromosomes.
		It is the principal male sex hormone and the "original" anabolic...
	www.sciencedaily.com /releases/2006/03/060306214707.htm (1799 words)

	HHMI News: Mutation Rate of Male Sex Chromosome Lower than Expected
		Genetic sequencing and analysis of regions of the X and Y chromosomes of humans, chimpanzees and gorillas, reveals a much smaller difference in mutation rates of the two sex-determining chromosomes, say researchers from the Howard Hughes Medical Institute at the Massachusetts Institute of Technology.
		The scientists then pinpointed the mutations in human sex chromosome by comparing each nucleotide variation with sequence data from the chimpanzee and gorilla X chromosome sequences.
		The higher incidence of Y chromosome mutations that produce some inherited diseases could be due to specific, highly mutable nucleotide positions—mutational "hotspots"—that represent departures from the normal rate of mutational.
	www.hhmi.org /news/page4.html (1020 words)

	Hens, cocks and avian sex determination
		The sex of an individual is generally determined genetically by genes on one of the two sex chromosomes.
		Critical to the question of sex determination in birds is the role of the two types of sex chromosomes.
		Like sex chromosomes in general, avian sex chromosomes are thought to have evolved from an ancestral pair of autosomes (Fridolfsson et al., 1998; Ellegren and Carmichael, 2001).
	www.nature.com /embor/journal/v2/n3/full/embor459.html (3559 words)

	SEX DETERMINATION
		The first 22 chromosome pairs are numerically labelled according to size, with 1 being the largest and 22 the smallest.
		The final pair consists of the sex chromosomes: ______ and ______.
		The sex of an offspring is determined by the ___________________________ that fertilizes the egg.
	www.soc.hawaii.edu /ws350/spr04/sexdeterm.htm (757 words)

	Sex Linkage (Site not responding. Last check: 2007-10-13)
		In many organisms, sex of the individual is determined genetically by the presence or absence of particular sex-chromosomes.
		a gene carried on the sex chromosome that is present in both sexes; one copy in one sex, two in the other.
		These predictions agree with the data, so tooth color is controlled by a gene on the X chromosome and the green mutant allele is dominant to the white wild-type allele.
	web.mit.edu /esgbio/www/mg/sexlinkage.html (667 words)

	Amazon.com: The X in Sex: How the X Chromosome Controls Our Lives: Books: David Bainbridge (Site not responding. Last check: 2007-10-13)
		First explaining how the sex chromosomes-which he calls the "seeds of sexiness"-turn undifferentiated embryonic tissue into testicles or allow the formation of ovaries, Bainbridge goes on to demonstrate how the X chromosome is actually in control of the process.
		It is the male Y chromosome, and specifically the "Sry" gene on that chromosome, that actively sets out to make any cell blob containing it to turn into a male.
		The X in Sex: How the X Chromosome Controls Our Lives, by David Bainbridge writes a compelling and enjoyable book that explains the X and Y Chromosomes having a profound impact on our lives, determining what sex we will be and also influencing how we live.
	www.amazon.com /Sex-How-Chromosome-Controls-Lives/dp/0674010280 (2366 words)

Try your search on: Qwika (all wikis)