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

2.2.1 Configuration and structure 形态与结构

2.2.2 Number and Size 数目和大小

2.2.3 Karyotype Analysis 组型分析

2.3 Mitosis

2.4 Meiosis

2.5 Life history of propagation

Terms – p63-64, 72, 134-136, 139-140

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

2.2.1 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 con

tain multiple repeates of simple, short DNA sequences. I

n humans the repeat sequence is TTAGGG. Telomere le

ngth is maintained by the enzyme telomerade, a protein

that contains RNA complementary to the telomere repea

t DNA sequence, that acts as a template for extension of

the telomere. Telomerase is absent from somatic cells bu

t reappears in tumor cell. Telomere is the mark to the ag

ing 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 2-2

2.2.3 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 ) p

19

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

See film

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 and meiosis .Ⅰ Ⅱ

Prophase of meiosis is subdivided into five stages: Ⅰ

leptotene, zygotene, pachytene, diplotene and diakinesis

(细线期、偶线期、粗线期、双线期和终变期 )

See film

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