1

Genes are in Nucleus of Eukaryotic Cells

1930s

2

Concluded: Genes are on Chromosomes

Prokaryotes: Circular chromosomes, Binary Fission

Eukaryotes: Linear chromosomes, Mitosis and Meiosis

3

Chromosome Number

Field Horsetail

4

Drosophila melanogaster Chromosomes

Diploid (2n = 8), 4 distinct chromosomes

3 autosomes, one pair of sex chromosomes (X & Y)

female male

polytene chromosomes

5

Rice Chromosomes

Oryza sativa 2n = 24; 12 pairs of chromosomes

6

Human Chromosomes22 pairs of autosomes, one pair of sex chromosomes (X & Y)

7

Descriptions of Eukaryotic Chromosomes

Unreplicated (G1) and Replicated (G2)

one chromatid two sister chromatids per chromosome per chromosome

8

Descriptions of Eukaryotic Chromosomes

All unreplicated chromosomes pictured

9

Descriptions of Eukaryotic Chromosomes

10

Eukaryotic Cell Cycle

Eukaryotes: Linear Chromosomes, Mitosis and Meiosis

Replicated Unreplicated

11

Mitosis - growth and healing

Interphase

Prophase - Chromosomes condense

Metaphase Chromosomes align independently

Anaphase Sister chromatids segregate

TelophaseCytokinesis

12

Mitosis - Prophase

A A

a ab b

BB

13

Mitosis - Metaphase & Anaphase

A A

a a

b b

BB

A A

a a

b b

B B

14

Mitosis - Telophase

A A

a a

b b

B B

15

Highlights of Mitosis

Diploid cellReplicated chromosomes

Diploid cellsUnreplicated chromosomes

A A a a b bBB

A

ab

B

16

Cytokinesis

Cell furrow Cell plate

17

Meiosis - Formation of Haploid Gametes

Diploid cell (one)Replicated chromosomes

Haploid cells (four)Unreplicated chromosomes

A A a a b bBB

A

a

b

B

A

b a B

18

Highlights of Meiosis

1. Chromosomes replicate once, cell divides twice

2. Homologous chromosomes pair then segregate

3. Chromosome number is reduced - diploid to haploid

4. Each gamete receives one of each type of chromosomewith one copy of each type of gene

OR

A

a b

B

a

A b

B

19

Stages of Meiosis I - Prophase

Leptonema - chromosomes condense

Zygonema - homologous chromosomes pair

Pachynema - Tetrads easily seen, crossing over occurs

Diplonema - Chiasma easily seen

Diakinesis - Terminalization, chiasmata resolved

20

Stages of Meiosis I - Prophase

Leptonema -chromosomes condense

Zygonema - homologous chromosomes pair

21

Stages of Meiosis I - Prophase

Pachynema - tetrads easily seen, crossing over occurs

Diplonema - chiasma easily seen

Diakinesis - terminalization, chiasmata resolved

22

Meiosis I

Diploid to Haploid

Reductional Division

23

Meiosis II

Haploid cell with replicated chromosomesto

Haploid cells with unreplicated chromosomes

24

Meiosis I & II

Figure 12.9

25

Compare and Contrast: Mitosis & Meiosis

Griffith et al. Introduction to Genetic Analysis.

26

Mitosis vs. Meiosis

Figure 12.11

27

Spermatogenesis vs. Oogenesis

Figure 12.13

In testis

continuousproduction

In ovaries

In 3 monthsfetus, allin Meiosis Iprophase

28

Gametogenesis in Plants

Figure 12.15.