Sex+Chromosomes

Michelle Salemi


=Sex Chromosomes= To understand what sex chromosomes are, it’s important to know what chromosomes themselves are. The definition of chromosomes is “A threadlike linear strand of DNA and associated proteins in the nucleus of eukaryotic cells that carries the genes and functions in the transmission of hereditary information” (thefreedictionary.com). Basically they hold the important information that makes people who they are, and determine everything from hair color to eye color to sex. More specifically, in the human genome, there are 2 sex chromosomes and there are 44 autosomes (carry other genes) making a total of 46 (about.com). The two sex chromosomes are represented as an X and a Y.
 * Overview **

 **The Beginning: Sexual Reproduction ** The female carry an egg or ovum, also known as a gamete and the male have sperm, a smaller type of gamete. During sexual intercourse, the male releases sperm which then searches to fertilize the egg. If this is accomplished, then there is what we call a zygote, which constitutes the first stage in the organism's development. Such zygotes contain DNA derived from both the mother and the father, and this provides all the genetic information necessary to form a new individual. Now more specifically, the sex chromosomes will determine the sex of the future child. As for humans, the egg can only carry an X chromosome, whereas a sperm may carry either an X or a Y. Therefore the male sperm determines the sex of the resulting zygote. If the zygote has two X chromosomes it will develop into a female, if it has an X and a Y chromosome, it will develop into a male. This is not the same for all animals on the planet. Some do not have the X and Y chromosomes, but rather another set.  **X Chromosome **  Both male and female have an X chromosome. Normal females carry two and normal males carry only one. The X chromosome carries hundreds of genes. Only a minority of the genes on the X have anything to do with sex determination (medterms.com). Since males have only a single X chromosome, the inheritance process of genes on the X follows special rules. Almost no gene on the X has a counterpart on the Y, and genes on the X are expressed in males Genes inherited in this manner are said to be sex-linked or, more precisely, X-linked (medterms.com). This term X-linked basically means the instead of just associated, this gene travels with the X chromosome and therefore is part of the X chromosome. Some examples of genes on the X chromosome include those for the episodic muscle weakness, ocular albinism, infantile spasm syndrome and red-green color blindness.  The X-chromosome is notably larger and has a more active euchromatin region than its Y-chromosome counterpart. Euchromatin refers to a lightly packed form of DNA that is rich in gene concentration, and is often (but not always) under active transcription (medterms.com).

**Y Chromosome ** Along with one X chromosome, the Y chromosome is the other half of the pair found in a normal male. At one time, the Y chromosome was thought to be obsolete, but it was proven otherwise. It is known to contain at least 20 genes, some of them unique to the Y including the male-determining gene and male fitness genes (medterms.com). The fitness gene is thought to be responsible for the development of sperm. It is true that some genes on the Y chromosome have counterparts on the X chromosome. Yet there are a number of genes that have been Y-linked, as in only specific to the Y chromosome. Some examples are TSPY (testis-specific protein), SRY (sex-determining region), and more (medterms.com). A useful concept of the Y chromosome is that it is passed unchanged from father to son. Therefore, it is key to tracking family with a DNA method. All men have essentially the same Y chromosome. It is also said that the Y chromosome has lost more than half of its original genes over the course of its existence. Some scientists predict it may potentially lose complete function within the next 10 million years (Wikipedia.com). The human Y-chromosome is particularly exposed to high mutation rates due to the environment in which it is stored. It is passed exclusively through sperm, which undergo multiple cell divisions therefore increasing its chances for mutation. This can prevent sperm production and thus causes male infertility (hhmi.org).  **<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">Chromosomal disease and disorders ** <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">With the sex chromosomes, many disorders are able to develop for different reasons. There is the existence of humans having more than two chromosomes. It is possible for some men to have two XX’s and a Y. This is known as Klinefelter’s syndrome, and it is the most common sex chromosome disorder in males. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;"> The principal effects are development of small testicle and reduced fertility. A variety of other physical and behavioral differences and problems are common, though severity varies and many boys and men with the condition have few detectable symptoms. (nichd.nih.gov). About one in every 50 males has an extra X chromosome. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">On the flip side, it is possible for women to have three X’s, which is referred to as “Triple X Syndrome.” There is usually no distinguishable difference to the naked eye between women with triple X and the rest of the female population. Another possibility in females is a single X instead of a double X ("X0"), which is referred to as Turner syndrome. Symptoms of Turner Syndrome in infant females include swollen hands and feet, and wide and webbed neck. In older females, symptoms include broad, flat chest shaped like a shield, absent menstruation, droopy eyelids, and short height (ncbi.nlm.nih.gov). <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;"> **<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">Social Implications ** <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">The XX chromosome pairing in comparison with the XY chromosome pairing clearly creates sex differences, as with female and male. With this, it has been considered that the roles of the human X and Y chromosomes in conferring such sex differences can also have effect on gender behavioral differences (Craig, 2004). This would be implying that sex determent genes affect outward behaviors between males and females. This theory overlooks societal influences on gender differences. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">Some people view sex chromosomes simply as the determiner of the sex of a child, but not the gender. It is argued that gender is a set of social, cultural, psychological traits that are associated with one sex or the other. It is learned. <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">Within the realm of sexual communication, the topic of sex chromosomes isn’t directly applicable, but more of a starting point for discussion. Studies continue to be conducted on how these chromosomes influence a person’s personality and therefore, how they interact with others. The nature of the mechanisms underlying observed sex differences in human behavior continues to be debated (Craig, 2004). <span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">

**<span style="font-family: "Times New Roman","serif"; font-size: 12pt; line-height: 200%;">References ** <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Bailey, R. (n.d.). Chromosomes and Sex. //Biology//. Retrieved April 6, 2011, from <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">[]

<span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Chromosome - definition of chromosome by the Free Online Dictionary, Thesaurus and Encyclopedia.. (n.d.). <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> //Dictionary, Encyclopedia and Thesaurus - The Free Dictionary//. Retrieved April 8, 2011, <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> from []

<span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Craig, Ian W. Harper, Emma. & Loat, Caroline S. (2004) “The Genetic Basis for Sex <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Differences in Human Behavior: Role of the Sex Chromosomes”. Retrieved 6 April 2011. <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">[|http://web.ebscohost.com.proxy2.library.illinois.edu/ehost/pdfviewer/pdfviewer?sid=3b15] <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">[|ce46-a130-4aa3-80ba-f16af0f43110%40sessionmgr4&vid=4&hid=7] <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Klinefelter Syndrome. (2007, May 24). //NICHD - The Eunice Kennedy Shriver National Institute// //<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">of Child Health and Human Development Official Home Page //<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">. Retrieved April 8, 2011, from <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> [] <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Y chromosome - Wikipedia, the free encyclopedia. (2011, April 7). //Wikipedia, the free// //<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">encyclopedia //<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">. Retrieved April 8, 2011, from [] <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Page, D. (1999, December 1). Mutation on Y Chromosome Stops Sperm Production. //Howard// //<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Huges Medical Institute //<span style="font-family: "Times New Roman","serif"; font-size: 12pt;">. Retrieved April 6, 2011, from [|www.hhmi.org/news/page3.html] <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">PubMed Health. (2009, November 14). //Turner Sydrome//. Retrieved April 6, 2011, from <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">[|www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001417/] <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Sex Chromosomes. (2003, May 27). //MedicineNet.com//. Retrieved April 6, 2011, from <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">[|www.medterms.com/script/main/art.asp?articlekey=6049] <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;"> <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">Latest News - Softpedia. (n.d.). //Latest News - Softpedia//. Retrieved April 8, 2011, from <span style="font-family: "Times New Roman","serif"; font-size: 12pt;">[]
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