Chapter 2 Chromosome Action 第二章 遗传的染色体基础 2.1 Sexual Reproduction 2.2 Chromosome Morphology and Number Configuration and structure 形态与结构 Number and Size 数目和大小 Karyotype Analysis 组型分析

2.3 Mitosis 2.4 Meiosis 2.5 Life history of propagation

Terms – p63-64, 72, , Prokaryote Heterochromatin Eukaryote Euchromatin DNA replication Secondary constriction Cell division Telomere Synthesis Chromosomal satellite Mitosis Histone Interphase Nucleosome Prophase

Metaphase Asexual reproduction Anaphase Zygote Telophase Meiosis Centromere Bivalents Chromatid Tetrad Cytokinesis Synapsis Gamete Ovary Germ cell Testis Polar bodies Ovum/spermatozoa

2.1 Sexual Reproduction 2.2 Chromosome Morphology and Number Chromosome morphology satellite secondary constriction short arm primary constriction Centromere long arm telomere

Telomere( 端粒 ): Telomeres are not simply the ends of chromosomes and DNA molecules, but are specialized structures. They contain multiple repeates of simple, short DNA sequences. In humans the repeat sequence is TTAGGG. Telomere length is maintained by the enzyme telomerade, a protein that contains RNA complementary to the telomere repeat DNA sequence, that acts as a template for extension of the telomere. Telomerase is absent from somatic cells but reappears in tumor cell. Telomere is the mark to the aging process.

Chromosome morophology ( 染色体的形态 ): Eukaryote chromosomes are visible by light microscopy only during cell division, after they have replicated. 染色体的几个形态组：中间着丝粒、亚中央着丝 粒、亚端部着丝粒和端部着丝粒 ( 长臂 q, 短臂 p)

Chromosome structure 组蛋白八聚体 (2H2A 、 2H2B 、 2H3 、 2H4 ） DNA (200nts,70nm ， 1.75 圈 ) DNA nucleosome solenoid ( 螺线管） 一级 二级 supersolenoid ( 超螺线管） chromatin ( 染色单体 ) 三级 四级 p69 Nucleosome 核小体

2.2.2 Chromosome number and size Table Karyotype analysis p18

Cell division in eukaryotes occurs as series of phases known as the cell cycle. Replication from multiple origins. Replication bubbles form and these eventually meet and merge. Transcriptionally active regions are replicated first. Telomerase adds noncoding sequence that allow replication of chromosome ends. 真核生物细胞分裂所经历的各阶段称细胞周期。真核生物 染色体为多起点复制，复制泡形成，最后交汇合并。转录 活跃区域先复制。端粒酶加入到非编码序列区使染色体复 制终止。 2.3 Mitosis

Cell cycle: The cell cycle is the period between two divisions. It consists of four stages ： G1 （ gap1) S (synthesis) G2 (gap2) M （ mitosis 分裂期 ) p19

Mitosis ( 有丝分裂 ): Mitosis is divided into four phases: Prophase ( 前期 ) - Chromosomes condense Metaphase ( 中期 ) - Chromosomes are aligned on the equator of the cell Anaphase ( 后期 ) - The centromeres split, the two chromatids separate Telophase ( 末期 ) - Chromatids near the poles and then nuclear membranes form, chromosomes begin to decondense p21-22

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Meaning p21

2.4 Meiosis ( 减数分裂 ) : Meiosis involves two successive divisions resulting in the production of four cells each of which has half the number of chromosomes of the mother cell. There is no replication of DNA between the two divisions, which are known as meiosis Ⅰ and meiosis Ⅱ. Prophase of meiosis Ⅰ is subdivided into five stages: leptotene, zygotene, pachytene, diplotene and diakinesis ( 细线期、偶线期、粗线期、双线期和终变期 )

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Meaning of meiosis p25

2.5 Life history of propagation p27,28

MITOSIS OOGENESIS SPERMEOGENESIS Primary oocyte MEIOSIS I Primary spermatocyte Secondary oocyte Secondary spermatocyte first polar body MEIOSIS II Ovum Secondary Secondary Spermatids polar polar body body Differentiation Spermatozoa

Questions p29 Meiosis – problem 4