Homework 1 - Unit1.Chromosome Homework 1 .WhyistheY

Homework 1 - Unit1.Chromosome Homework 1 .WhyistheY

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Unit 1. Chromosome Homework  1.Y chromosome haplotypes and haplogroups are useful in population genetics in humans and are a powerful tool in looking at origins of humans.  Why is the Y chromosome a better marker than another autosome? The Y chromosome is a better marker than another autosome for simplicity reasons.  It is easy to follow because we know that only males will have it and will have received it from their father.  This knowledge allows us to follow the Y chromosome when studying the origins of humans rather than trying to sort out the X chromosome and where it came from.  2.Consider Metaphase in Mitosis and compare to Meiotic Metaphase 1 and 2 for a cell that has a 1N number=four.  Draw this out for each of these 3 stages.  Which of these has eight chromosomes aligned on the equator in homologous pairs?  Neither, Mitotic Metaphase has 4 chromosomes (8 chromatids each forming a homologous pair) aligned on the equatorWhich of these has eight chromosomes aligned on the equator in a straight line, one beneath the other? Neither 3.What does Walter Sutton’s work in Grasshoppers have to do with the establishment of the chromosome theory of inheritance?  What did his work showrelative to this? Sutton used his grasshopper studies to show that sperm cells contained half of the amount of chromosomes as grasshopper zygotes. These findings lead to the chromosome theory of inheritance where he determined that the gametes produced by grasshoppers made up half of theoffspring zygote. He then determined that two gametes must merge duringfertilization to create the chromosome pairs that we see in non-gametic cells. 
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4.How many autosomes does a human sperm carry? A human sperm carries 22 autosomes.  Each sex cell holds 23 single chromosomes, but one of them is the defining sex chromosome (X or Y chromosome). 5.In oogenesis, starting with one germ cell, the result is one egg.  In spermatogenesis, the result is four sperm.  Explain the process and how this occurs.  Use your text, there are great figures. In spermatogenesis the primary spermatocyte goes through meiosis I and produces two secondary spermatocytes.  Each of these spermatocytes then goes through meiosis II and produces two spermatids.  Each spermatid matures into spermatozoa.  In oogenesis the primary oocyte goes through meiosis I and produces one secondary oocyte and one polar body (A polar body has no function and will typically degenerate).  The secondary oocyte goes through meiosis II and produces an ootid and a second polar body.  This ootid is the resulting single egg.
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