BSC 315 Lecture Notes - Lecture 7: Sister Chromatids, Ploidy, Centromere
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28 Jan 2017
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Post-mendel evidence that chromosomes contain genes: fertilization: sperm contains a nucleus and little else. Therefore, genes must be in nucleus: chromosomes: chromosome behavior parallels mendelian allele behavior, specific genes located on specific chromosomes (sex-linked inheritance in fruit flies) Diploid cell: 2 copies of each chromosome (except sex chromosomes). Diploid chromosome number = 2n: members of the pair are homologous chromosomes, or homologs. Haploid cell: 1 copy of each chromosome. Chromosomes are visible only during mitosis and meiosis, but not interphase. Germline = egg or sperm and precursor cells. Beginning of mitosis: each chromosome has 2 chromatids. End of mitosis: each chromosome has 1 chromatid. Sister chromatids: 2 parts of the same chromosome. Centromere position: metacentric - ~middle, acrocentric near one end. Chromosomes identified by: length, banding pattern with certain dyes, centromere position. Chromosomes and dna: each chromatid is a single dna molecule (average human chromosome: 10^8 base pairs and about 1000 genes)
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