2What are monosomies?The term "monosomy" is used to describe the absence of one member of a pair of chromosomes. Therefore, there is a total of 45 chromosomes in each cell of the body, rather than 46. For example, if a baby is born with only one X sex chromosome, rather than the usual pair (either two X's or one X and one Y sex chromosome), the baby would be said to have "monosomy X." Monosomy X is also known as Turner syndrome.
3Turner syndromeTurner syndrome is typically caused by what is called nondisjunction. If a pair of sex chromosomes fails to separate during the formation of an egg (or sperm), this is referred to as nondisjunction. When an abnormal egg unites with a normal sperm to form an embryo, that embryo may end up missing one of the sex chromosomes (X rather than XX). As the embryo grows and the cells divide, every cell of the baby's body will be missing one of the X chromosomes.
5symptoms of Turner syndrome: affects growth and sexual development.Girls with this disorder are shorter than normal, and may fail to start puberty when they should. This is because the ovaries (which produce eggs, as well as the sex hormones estrogen and progesterone) fail to develop properly.Women with Turner syndrome appear to have a stocky appearance, arms that turn out slightly at the elbow, a receding lower jaw, a short webbed neck, and low hairline at the back of the neck.Other medical symptoms include: lymphedema (swelling of hands and feet), heart and/or kidney defects, high blood pressure, and infertility (inability to have children).
6How is Turner syndrome treated? Hormone replacement therapy is the best way to treat this disorder. Teenagers are treated with growth hormone to help them reach a normal height. They may also be given low doses of androgens (male hormones which females also produce in small quantities) to increase height and encourage normal hair and muscle growth. Some patients may take the female hormone estrogen to promote normal sexual development.
7Klinefelter syndromeKlinefelter syndrome is typically caused by what is called nondisjunction. If a pair of sex chromosomes fails to separate during the formation of an egg (or sperm), this is referred to as nondisjunction. When that egg unites with a normal sperm to form an embryo, that embryo may end up with three copies of the sex chromosomes (XXY) instead of the normal two (XY). The extra chromosome is then copied in every cell of the baby's body.
10symptoms of Klinefelter syndrome: Many people with this disorder have no idea they have it until they hit puberty or try to have children. At puberty, men with this syndrome often develop more breast tissue than normal, have a less muscular body, and grow very little facial or body hair. When men with Klinefelter syndrome try to have children, most discover that they are sterile because they cannot produce sperm. Learning disabilities (not categorized as mental retardation) are also a common problem for them.
12What are syndromes?the term “syndrome” is used to describe the phenotype abnormalities. Some irregular numbers are associated with a complex of abnormalities that may include morphological, physiological, and psychological deviations from normal. Such a complex of symptoms is called a syndrome.
13Some of the more common and well-known syndromes associated with chromosomal abnormalities are listed in the table 1:Phenotype or syndromeTotal No. of chromosomesSex chromosomes complementNo. of Barr bodies per nucleusNormal femaleNormal male46XXXY1Sterile male with klinefelte syndrome47, 48, 49XXY, XXXY, XXXXY1, 2, 3Sterile female with Turner syndrome45XMale with XYY karyotype47XYYFemale with trisomy XXXX2Down syndrome (trisomy21)XX or XY1 f, 0 mEdwards syndrome (trisomy18)Patau syndrome (trisomy13)