[BIO380H5] - Final Exam Guide - Everything you need to know! (72 pages long)

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29 Nov 2016
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Bio 380 human development lecture 2. Of all potential conceptions, about 1/3 of them abort spontaneously; this is probably due to the. About of these abortions occur before pregnancy is detected. As a woman gets older, the higher the chance of chromosomal abnormality during pregnancy, this is probably due to their extended arrest at prophase i. Chromosomal abnormalities are caused by the improper separation of the chromosomes during either the first or second stage of meiosis. Trisomy occurs when there are 47 chromosomes within the karyotype as opposed to 46 (normal: ex. Monosomy occurs when there are 45 chromosomes (one of the sex chromosomes are missing: ex. Turner"s syndrome is caused by monosomy in the 23rd chromosome: embryo"s with monosomy usually aren"t viable, they have short stature, cognitive defects, a webbed neck, childish characteristics and sterile gonads. Spermatogenesis occurs within the seminiferous tubules of the testis.