Cellular Reproduction

Question 1

Organization of Chromosomes

Answer 1

Chromatin is bound by histones into 10nm fiber (nucleosome beads), 30 nm fiber, 700 nm fiber (metaphase chromosome)

Question 2

Euchromatin vs heterochromatin

Answer 2

euchromatin: loosely packed
hetero: during interphase, tightly condensed

Question 3

Cell Cycle

Answer 3

G1: cell growth
G1/S checkpoint: if passed, cell commits to dividing
S: DNA replication
G2: prepare for mitosis
G2/M checkpoint: if passed, cell can divide
Mitosis
spindle assembly checkpoint

Question 4

Control of Cell cycle

Answer 4

CDKs must bind to cyclin to progress through cycle

Question 5

Cyclins

Answer 5

Mitotic Cyclins: G2/M checkpoint, bind mitotic CDKs using MPF
G1 Cyclins
S1 cyclins

Question 6

Regulation of Cdk-Cyclin

Answer 6

1. availability of cyclin: builds up during phases

2. phosphorylation of CDKs

Question 7

Chromosomes and DNA through cell cycle

Answer 7

Chromosomes: G1, S, G2, prophase, metaphase, telophase: 4
anaphase: 8

DNA molecules: 4 to 8 in S, back to 4 in telophase

chromosomes = number of centromeres
DNA = number of chromatids

Question 8

Meiosis I

Answer 8

separation of homologous chromosome pairs, reduction of chromosome number by 1/2

Prophase I: synapsis, crossing over
Anaphase I: random distribution of chromosomes (more genetic variation)

Question 9

Meiosis II

Answer 9

separation of sister chromatids, equational division

Question 10

Cohesin

Answer 10

protein that holds chromatids together
breakdown of cohesin allows sister chromatids to separate in mitosis

cohesin broken down between homologs in meiosis, but maintained by shugoshin at centromere