上海交通大学遗传学lecture1精选.ppt

Genetics Yueping CAO Plant Science Differences between prokaryotic and eukaryotic cells.真核细胞和原核细胞的区别 Examples of the number of chromosome in various species  -Most animal somatic cells are _Diploid____. Diploid cells have _2_ sets of chromosomes. Most animal gametic cells are _Haploid_. Haploid cells have _1_ set of chromosomes. -Plant species vary in the number of sets of chromosomes. For example, wheat is a _Hexaploid__ with _6_ sets of chromsomes. Homologous chromosome（同源染色体） Chromosomes -During mitosis and meiosis, stained chromosomes are visible with a light microscope.在有丝分裂列和减数分裂过程中在光学显微镜下可以看到染色体。 -What are chromosomes composed of? 染色体的组成是: DNA, protein and RNA Homologous chromosomes ——- a pair (in diploids) of essentially identical chromosomes that join and recombine DNA in meiosis. 同源染色体是是在减数分裂中可以重新结合在一起的大小形态相同的染色体（体条来自父本，一条来自母本）。 -Humans have 23 pairs of homologous chromosomes. -Chromosomes can be classified based on size and position of centromere. -Homologous chromosomes are the same size with the exception of the sex chromosomes. Homologous chromosomes -Chromosomes can be classified based on size and position of centromere. -Homologous chromosomes are the same size with the exception of the sex chromosomes. Below are 2 homologous chromosomes. One of these chromosomes would be from this individual’s mother and the other from the father. Each homologous chromosome consists of two chromatids. The two chromatid on a chromosome contain identical genetic information. This information was recently replicated during the S phase of the cell cycle. The two homologous chromosomes would carry alternative alleles for genes. For example, if the individual is heterozygous Aa, one homologous chromosome would carry the A allele and the other chromosome would carry the a allele. Because two chromatids on the same chromosome carry identical genetic information, both chromatid 1 and 2 would carry the A allele and chromatids 3 and 4 would