BIOL239 Lecture 4: BIOL239set4 chromosomes (1)
17 Feb 2016
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Document Summary
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. Use of dyes for differential staining of cytoplasm, nucleus and nuclear structures, including chromosomes. 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. States that hereditary information is on genes and that genes are located on chromosomes. Also that egg and sperm contribute equally to the genetic endowment of offspring through their nuclei. 1901 - the x and y chromosomes determine sex in grasshoppers. Soon others confirmed presence of separate sex chromosomes in other species. One sex carries 2 of the same sex chromosome, the other carries one of each (not true in all species) Platypus: studies in pnas and nature; females are (xxxxx)x2, males are xxxxxyyyyy.
