Cell Bicycle

Question 1

What are the four phases of the cell cycle?

Answer 1

M cycle, G1 phase, S Phase, and G2 Phase

Question 2

Are yeast cells haploid or diploid?

Answer 2

Haploid

Question 3

What is purifying selection?

Answer 3

A very important sequence that stays in nearly all organisms

Question 4

What do cdc2 mutant yeast do? What is it caused by?

Answer 4

cdc2 mutant yeast replicate way too much and it is caused by losing the gene altogether

Question 5

What happens when the cdc2 gene is restored in the mutants?

Answer 5

Restores the genotype

Question 6

What happens when human cdc2 is put into mutant cdc2 yeast?

Answer 6

Genome is STILL restored (cus amino acids are basically the same)

Question 7

At what rate is cyclin synthesized in the cell?

Answer 7

Constant, always being made

Question 8

What regulates Cdk activity?

Answer 8

Cyclin

Question 9

What triggers M-phase?

Answer 9

Cyclic protein synthesis

Question 10

What triggers G1?

Answer 10

Cyclin degradation

Question 11

How does ubiquitin mediated protein degradation work?

Answer 11

Ubiquitin grabs on to cyclin -> puts it in a proteasome -> leaves proteasome -> cyclin is degraded

Question 12

What catalyzes ubiquitin?

Answer 12

Ubiquitin ligase

Question 13

What triggers the end of M-phase/cause entry into G1?

Answer 13

Ubiquitylation and degradation of cyclin

Question 14

What does Wee1 do to Cdk?

Answer 14

Phosphorylates it to inactivate it

Question 15

What does cdc25 do to Cdk?

Answer 15

Removes inhibitory phosphates from Cdk to activate it

Question 16

What happens when Cdk is active and attached to a cyclin?

Answer 16

Cell division

Question 17

If a cell is not ready to continue to the next stage of the cell cycle, what is activated?

Answer 17

Wee1

Question 18

If a cell IS ready to move onto the next step of the cell cycle what does it activate?

Answer 18

Cdc2

Question 19

What holds two chromosomes together during pre S phase?

Answer 19

Cohesion proteins

Question 20

What are the stages of mitosis in order?

Answer 20

1. Prophase
2. Prometaphase
3. Metaphase
4. Anaphase
5. Telophase
6. Cytokinesis

Question 21

What is the G2-M transition influenced by?

Answer 21

Cell size, DNA damage, and DNA replication

Question 22

What influences the Metaphase-Anaphase transition?

Answer 22

Chromosome attachments to spindle

Question 23

What influences the restriction point of the start? (Right before S phase)

Answer 23

Growth factors, nutrients, cell size, and DNA damage

Question 24

What happens in prophase?

Answer 24

Replicated chromosomes condense and the mitotic spindles begin to form along with the two centrosomes beginning to move towards the poles of the cell

Question 25

How do microtubules attach to chromosomes?

Answer 25

The kinetochores which are bounded to the chromosome on the centromere

Question 26

How do the centrosomes push away from each other?

Answer 26

Motors push the spindles in an anti parallel fashion

Question 27

What happens during prometaphase?

Answer 27

The nuclear envelope is broken down (in humans at least) and the chromosomes begin to attach to spindles

Question 28

What happens during metaphase?

Answer 28

Chromosomes are aligned in the middle of the cell

Question 29

What happens during anaphase?

Answer 29

Cohesions are removed from the chromosomes and finally begin to be pulled apart

Question 30

How do microtubules pull chromosomes apart?

Answer 30

The microtubules shrink

Question 31

What happens during telophase?

Answer 31

The two sets of daughter chromosomes reach the poles and the cell begins to pinch off from the contractile ring also the nuclear envelope starts reforming

Question 32

What pinches the contractile ring?

Answer 32

Actin

Question 33

During prometaphase, what does search and capture refer to?

Answer 33

The kinetochore of the chromosomes

Question 34

Where does the energy to pull the chromosome come from?

Answer 34

The energy released from the depolymerization of the microtubules

Question 35

What breaks down cohesions?

Answer 35

Separase (a protease)

Question 36

What inhibits separase?

Answer 36

Securin

Question 37

What frees separase from securin?

Answer 37

APC

Question 38

What is APC?

Answer 38

Anaphase promoting complex (a ubiquitin ligase that targets mitotic cyclin ands securin for degredation)

Question 39

For the metaphase-anaphase transition, what must happen before APC can activate?

Answer 39

Spindles must be attached to spindle

Question 40

What are the main differences between meiosis and mitosis?

Answer 40

- in meiosis, the duplicates homologous are paired - meiosis results in 4 haploid daughter cells, mitosis results in two diploid daughters

Question 41

What holds sister chromatids together? (Same chromosome just duplicated)

Answer 41

Cohesions

Question 42

What holds homologous chromosomes together?

Answer 42

Chiasmata (during meiosis 1)

Question 43

When does recombination happen?

Answer 43

Before the chromosomes line up (metaphase 1)

Question 44

When do homologous chromosomes segregate?

Answer 44

Anaphase 1

Question 45

When do alleles separate?

Answer 45

Meiosis 2

Question 46

What are the 3 stages of meiosis?

Answer 46

Meotic S phase -> Meiosis 1 -> Meiosis 2

Question 47

What happens during anaphase 1 in meiosis?

Answer 47

Cohesions are removes from the chromosome arms and homologous pairs are pulled apart Cohesions are centromeres are SAFE, sisters stick together

Question 48

What happens during anaphase 2 in meiosis?

Answer 48

Cohesions are removes at centromeres, sisters are pulled apart