The cell cycle, stem cells, cancer

Question 1

Name the four phases of the cell cycle

Answer 1

G1, S, G2, M

Question 2

What are the 5 sections the M phase of mitosis is split into?

Answer 2

Prophase, prometaphase, metaphase, anaphase, telophase

Question 3

What happens in prophase of mitosis?

Answer 3

The nuclear envelope has dissolved in G2
The chromosomes fully condense
The early mitotic spindle forms

Question 4

What happens in prometaphase?

Answer 4

The kinetochore microtubules begin connecting to the kinetochores

Question 5

Describe metaphase

Answer 5

Chromosomes align at equator along the metaphase plate
Centrosomes at spindle poles

Question 6

Describe anaphase

Answer 6

Sister chromatids separate
Spindles contract

Question 7

Describe briefly telophase and cytokinesis

Answer 7

Chromosomes reach poles of cells
Nucleus reforms
Spindles degrade

Question 8

What holds the chromatids together? Describe the structure

Answer 8

Cohesin
A multi subunit protein, which forms a dimer loop trapping 2 strands of DNA inside

Question 9

What are the stages of chromosome packaging?

Answer 9

1. Beads on a string chromatin
2. Chromatin fibre of nucleosomes
3. Chromosome coils to create condensed form - using condensin and cohesin

Question 10

What are chromosomes condensed by? Describe the process

Answer 10

Condensin creates dimer loops
Coordination with cohesin allows chromosomes to condense into 300nm fibres

Question 11

What are the SMC complexes?

Answer 11

Structural maintenance of chromosomes complexes
Cohesin and condensin

Question 12

How many centrioles in a centrosome

Answer 12

2

Question 13

What are the mitotic spindles made of?

Answer 13

Microtubules

Question 14

How many microtubules in a spindle?

Answer 14

3

Question 15

What attaches astral microtubules to the cell membrane?

Answer 15

Dynein

Question 16

What tightens the mitotic spindle?

Answer 16

Kinesin-14

Question 17

What expands the mitotic spindle?

Answer 17

Kinesin-5

Question 18

What proteins move the chromosomes to the poles of the cell?

Answer 18

Kinesin 4 and Kinesin 10

Question 19

What is the centromere?

Answer 19

Where the chromosomes are joined at a single point along their length
Dense, tightly structured DNA

Question 20

How does the centromere attach to the spindles?

Answer 20

The centromere has a kinetochore region, which has several proteins
DNA has low affinity for microtubules, and the centromere has no genes

Question 21

What are the 3 layers of the kinetochore? What are their function?

Answer 21

1. Checkpoint - collar - attaches to spindles
2. Outer - structural
3. Inner - binds to DNA

Question 22

What orients chromosomes so one chromatid faces each side?

Answer 22

The kinetochore and kinesins 4, 10 enable the chromosome to walk to the ends of the spindle fibre

Question 23

What pulls the chromatids apart?

Answer 23

Separase enzyme, which is part of the anaphase promoting complex

Question 24

How do spindles shorten?

Answer 24

The + end is attached to the kinetochore, and tubulin begins to leave - depolymerisation of the plus end.
Then, the force pulls the kinetochore closer to the poles.

Question 25

Is mitosis or meiosis the source of genetic diversity?

Answer 25

Meiosis

Question 26

What are the names of the 5 phases that prophase of meiosis 1 is split into?

Answer 26

Leptotene Zygotene Pachytene Diplotene Diakinesis

Question 27

What kind of gametes does meiosis produce?

Answer 27

Haploid

Question 28

When does bivalent formation occur?

Answer 28

Meiosis 1

Question 29

What are the points where homologous chromosomes join called?

Answer 29

Chiasmata

Question 30

What happens in leptotene?

Answer 30

Duplicated chromosomes start to condense

Question 31

What happens in zygotene?

Answer 31

Synaptonemal complexes form, synapsis begins, joining chromosomes

Question 32

What happens in pachytene?

Answer 32

Synapsis ends, crossing over begins - breakage of DNA and refusion with chromatids

Question 33

How can you tell a cell has entered diplotene?

Answer 33

Chiasmata are visible Bivalents/tetrads visible under microscope

Question 34

What happens in diakinesis?

Answer 34

The nuclear envelope fragments Homologous chromosomes ready for metaphase Bivalents associate with meiotic spindle

Question 35

What is the synaptonemal complex?

Answer 35

A collection of proteins and chromosomal structures Zip the chromatids together

Question 36

What is pulled apart in mitosis and meiosis?

Answer 36

Mitosis = chromatids Meiosis = chromosomes, then chromatids

Question 37

Describe the mitosis daughter cells in terms of n and C

Answer 37

2n 2C

Question 38

Describe the meiosis daughter cells in terms of n and C

Answer 38

n C

Question 39

What does n mean?

Answer 39

Ploidy number. Number of complete sets of chromosomes in a cell - haploid = n, diploid = 2n

Question 40

What does C mean?

Answer 40

DNA content in the cell - 2C = diploid

Question 41

What forms the cleavage furrow in cytokinesis?

Answer 41

Actin and myosin contractile ring

Question 42

How does cytokinesis occur in plants?

Answer 42

Construction of the phragmoplast/cell plate

Question 43

What is a holliday junction?

Answer 43

Crosswise structure between 2 duplexes of DNA