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Pregnancy and Chromosomal AbnormalitiesBY: Amna Adnan | Category: Genetics | Submitted: 2010-06-25 04:51:29
Article Summary: "Women possess chromosomal abnormalities when they exceed the age of 30. These abnormalities result in causing many syndromes like Down's syndrome, turner's syndrome and Klinefelter syndrome..."
Science has revealed a long time ago that when the age of the mother exceeds thirty years, she gets the chances of giving birth to an abnormal child. The child might have chromosomal abnormalities.
Pregnancy and chromosomal abnormalities:-
Pregnancy is a natural process in which a woman keeps her child inside her womb for nine months or 280 days and then gives birth to a child. As described earlier, if a mother is 35 years of age or above, she might have chances of chromosomal abnormalities. These chromosomes when start the process of crossing over during meiosis of the sex chromosomes, they might cross in an abnormal way. For example, when chromosomes start dividing, they either exchange their parts or the whole chromosome. Sometimes it happens that instead of crossing over of some part of the chromosome whole chromosome comes in the sex cells. Now due to abnormal division of chromosomes, one sex cell will have 24 chromosomes and the other will have 22. It should be kept in mind that among 23 chromosomes in each cell, there are 22 cells which are autosomal while one chromosome is the sex chromosome. Sex cells are haploids when they are alone but when the egg is fertilized with the sperm then they will become diploid.
Chromosomal abnormalities might occur due to the mutations in the genes. Some chromosomal abnormalities are genetic that is they run in the family and some are non-genetic. Either the mother or the father transfers these abnormalities into their children. Some chromosomal abnormalities are also due to the age of the mother. As the woman gets old, her chromosomes also start aging and might develop some abnormalities. These abnormalities usually result in the occurrence of different kinds of syndromes. Sometimes the chromosomal abnormality is so severe that it is impossible for the mother to give birth to that child and miscarriage occurs as a result.
Chromosomal abnormalities and syndromes:-
Down's syndrome is the most common abnormality which occurs in the children when the age of the mother is above 30 or 40.
Translocation trisomy 21 is the major cause of this syndrome. During the cell division, a part of chromosome 21 attaches to the chromosome 14. If the sperm or the ovum receives the chromosome 14 with a part of chromosome 21 or if the chromosome 21 with a missing part due to translocation comes during fertilization, then the cell division will be normal and there will be no chances of Down's syndrome but the mother or the father will be carriers of this syndrome. It is the mother in most of the cases whose chromosomes divide abnormally during cell division. There are less chances that father will transmit Down's syndrome in his child.
Turner's syndrome usually occurs in the girls. The girls born with this syndrome contain broad shoulders and they become sexually mature very late.
As it occurs mostly in girls that is why the girl born with turner's syndrome will have one normal X chromosome while the other X chromosome is either completely missing or some parts of it are missing. Due to this abnormality, girls ovaries develop abnormally and the girl faces problems in sexual maturity.
Unlike Turner's syndrome which affects girls, Klinefelter syndrome affects mostly boys. Features which appear in the boys as a result of this syndrome are tallness, less hair on face, masculine behavior is low and they have usually large breast than normal.
There are two X chromosomes in women while one X and one Y chromosome in men. Men inherit one X chromosome from the mother and one Y chromosome form father. But during Klinefelter syndrome a boy receives an extra X chromosome that is he has two X chromosomes and one Y chromosome.
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