BIOL239 Chapter Notes - Chapter 4: Chromosome, Gamete, Down Syndrome
6 Mar 2017
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1854 studies with frogs and sea urchins showing union of male and female gametes. 1879 observation of threadlike structures in the nuclei of salamander cells during cell division. 1880 advances in microscopic techniques use of dyes for di erential staining of cytoplasm, nucleus and nuclear structures, including chromosomes. Early 1900s linking of chromosomes to the mendelian principles of segregation and independent assortment proposed that each egg or sperm contains only one of each chromosome of a pair. chromosomal theory of inheritance. 1901 - the x and y chromosomes determine sex in grasshoppers. Soon others con rmed presence of separate sex chromosomes in other species one sex carries 2 of the same sex chromosome, the other carries one of each. States that hereditary information is on genes and that genes are located on chromosomes and that egg and sperm contribute equally to the genetic endowment (inheritance) of o spring through their nuclei. Birds, butter ies, some reptiles: males zz females zw.
