BIOL 111 Lecture Notes - Lecture 15: Thomas Hunt Morgan, Gel Electrophoresis, Barr Body
Document Summary
Thomas hunt morgan- studied genes linked to sex chromosomes using flies. Y chromosome- 78 genes coding 25 proteins, mainly sex determinate. Dax 1 gene- located on the x gene. On the y chromosome crossing over does not occur. Short tandum repeats- repeated sequences of dna, mostly noncoding. Gel electrophoresis- short fragments travel further while longer stay near the top. Most sex linked traits are x linked traits because the x is bigger and contains more genes. Gene= sex linked trait while a trait = a x or y linked trait. Males are hemizygous for all sex linked genes (phenotype= genotype) X inactivation- in female mammals, one x chromosome in each cell becomes inactive to maintain balance. Xic center as xist gene- encodes rna which coats the chromosome and condenses inactive barr bodies. Linked genes- on same chromosome and inherited as a packaged deal . Crossing over can occur between homologous chromosomes as long as they are far apart.
