D. How do cells count chromosomes? 1. transcription factors on autosomes and X chromosome 2. XX has two copies of gene for protein in X, XO or XY has one copy of gene for protein on X E. human and other mammals 1. gender determined by male promoting gene on Y X:A chrom. gender 0.5 XY male 1.0 XX female 0.5 X female 1.0 XXY male 2. sex determined at level of individual, not at level of cell a. chromosomal complement determines if primordial gonad cells are testis or ovary - if testis, secrete testosterone male - if ovary, no testosterone female b. gender determined by sry gene, on Y chromosome - identified using sex reversal in mice and human - XX + small piece of Y translocated to X
D. How do cells count chromosomes? 1. transcription factors on autosomes and X chromosome 2. XX has two copies of gene for protein in X, XO or XY has one copy of gene for protein on X E. human and other mammals 1. gender determined by male promoting gene on Y X:A chrom. gender 0.5 XY male 1.0 XX female 0.5 X female 1.0 XXY male 2. sex determined at level of individual, not at level of cell a. chromosomal complement determines if primordial gonad cells are testis or ovary - if testis, secrete testosterone male - if ovary, no testosterone female b. gender determined by sry gene, on Y chromosome - identified using sex reversal in mice and human - XX + small piece of Y translocated to X