Notes from 3/9-3/14
Notes from 3/9-3/14 Bios 2250
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This 3 page Class Notes was uploaded by hw767714 on Saturday April 9, 2016. The Class Notes belongs to Bios 2250 at Ohio University taught by Dr. Sugiyama in Winter 2016. Since its upload, it has received 9 views. For similar materials see Genetics in Human Society in Biology at Ohio University.
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Date Created: 04/09/16
BIOS 2250 notes 3/9 – 3/14 Amniocentesis – a medical procedure used in prenatal diagnosis of chromosomal abnormalities, fetal infections, sex determination, etc. This procedure is performed by taking a small sample of amniotic fluid from the amniotic sac that surrounds the fetus. This is the most common way to collect fetal cells. However, you cannot th perform this procedure until at least the 16 week of pregnancy to ensure that there is enough amniotic fluid. This procedure can test for more than 100 different disorders. Conditions that suggest the use of amniocentesis include: ▬ A maternal age that is over 35 ▬ A previous child with a chromosomal aberration ▬ One or both of the parents has a chromosomal rearrangement ▬ If the mother is a carrier of an X-linked disorder A new method under development is to try and obtain fetal cells from the mother’s bloodstream. This method is still being researched There is a very small number of fetal cells that end up in the mother’s blood stream and it is difficult to isolate them. There is less than 1 in 100,000 fetal cells in the mother’s blood stream. This method will end up being much safer than other methods Chromosome disorders are classified by the different variations in chromosome numbers Polyploidy – a chromosome disorder where there are more than 2 haploid sets of each chromosome. ▬ Triploidy – a polyploidy chromosome disorder where there are 3 haploid sets of each chromosome. ▬ Occur in 1/10000 live births and usually only survive a few hours after birth ▬ Caused by errors in meiosis, dispermy (multiple sperm fertilization), and errors in mitosis ▬ Around 15%-18% of all cases result in spontaneous abortion Aneuploidy – a chromosome disorder where chromosomal number varies by less than 1 haploid set. ▬ Monosomy – lacking 1 haploid chromosome set ▬ Trisomy – having 1 extra haploid chromosome set Monosomy – when one of the chromosomal sets are not complete. ▬ Autosomal monosomy is pretty rare and is lethal. ▬ A majority of the cases are lost in early development ▬ X monosomy is not lethal. Turner syndrome 45x is the only monosomy child that can make a live birth. 97%-99% of 45x individuals die before birth. This occurs in about 1 of 2,000-10,000 births. BIOS 2250 notes 3/9 – 3/14 Females with this condition are short, have wide chests, rudimentary ovaries, and abnormal sexual development. Autosomal trisomy – A chromosomal disorder where the individual has 47 total chromosomes. A large number of autosomal trisomies are found in miscarriage embryos. The lethality of the disorder depends on the affected chromosome Autosomal trisomies that allow live births include trisomy 13, trisomy 18, and trisomy 21. Trisomy 13 – Patau syndrome Occur in 1 in 15,000 births Lethal, the average survival time is about 6 months after birth Facial malformations, eye defects, extra fingers and toes, etc. Severe malformations of the brain, nervous system, and heart. Parental age is a risk factor for trisomy 13 (Mothers aged over 36) Trisomy 18 – Edwards Syndrome Occur in 1 in 11,000 births The average survival time is 2-4 months Usually very small at birth, mentally retarded, and grows very slowly Malformation of heart, hands, and feet For unknown reasons, 80% of all trisomy 18 babies are girls Maternal age is a risk factor Trisomy 21 – Downs Syndrome First chromosomal abnormality discovered in humans (1959) Occur in 1 in 900 live births Wide flat skulls, skin folds in corner of eyelids, spots on irises, and thick furrowed tongues Heart defects (Around 40% of people with Down Syndrome have heart defects) Higher risk of leukemia and ear infections Life expectancy is around 60 years old now Sex chromosome aneuploidies are more common than autosomal aneuploidies. About 1 in 1500 live births Klinefelter Syndrome – 47 chromosomes, XXY ▬ Symptoms usually don’t kick in until puberty and usually can be fixed with testosterone injections. ▬ Many have language and learning difficulties. XYY Syndrome appears in about 1 in 1000 male births. Usually end up being above average in height. BIOS 2250 notes 3/9 – 3/14