Lecture 8 Flashcards Preview

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Flashcards in Lecture 8 Deck (44)
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1

What is the name of the complex that marks cyclins for degradation and how is this achieved

The E3-ubiquitin ligase, anaphase promoting complex (APC) marks cyclins for degradation by ubiquitination

2

Explain the enzymes involved in the regulation of Cdk activity

Wee1 kinases is responsible for the phosphorylation and inactivation of Cdk. Whereas Cdc25 phosphatase removes a phosphate group from the inactive Cdk hence activating it. The interplay between Wee1 kinase and Cdc25 phosphatase determines that activity of Cdks.

3

Cyclins are a class of protein involved in the regulation of the cell cycle, explain how they interacts with their targets

Cyclins bind to cyclin-dependant kinases (Cdks) to activate them

4

What is the main difference between meiosis and mitosis

Meiosis resembles mitosis except there are extra steps that segregate homologous chromosomes

5

How are the cells that arise from gametes that contain an extra chromosome or missing homologue referred to

Aneuploid

6

Explain how pairing of chromosomes is facilitated in meiotic prophase I

Pairing is facilitated by the synaptonemal complex as well as DNA base pairing between homologues

7

What is the name of the protein inhibits the activity of the cyclin-cdk complex

p27

8

During which phase of mitosis do the sister chromatids condense

Prophase

9

What happens during anaphase

Sister chromatids are separated

10

Telophase corresponds to cytokinesis, T or F

T

11

How often to mammalian cells divide on average

Every 24 hours

12

What are the advantages of using yeast to study the cell cycle

Rapid division rate <1hr, cell cycle control genes almost identical to human, can be grown as haploids or diploids

13

What is the restriction or start point

A point in the cell cycle after G1 phase that determines the commitment of the cell to S phase and the completion of the rest of the cycle to G1 again

14

During which stage of mitosis do the chromosomes attach to the mitotic spindle via their kinetochores and the microtubules

Metaphase

15

What is the purpose of the G2/M checkpoint

Checks to see is all DNA has replicated and if the environment is favourable before assembling the mitotic machinery

16

What are Cdks and how do they act

Cyclin dependant kinases (Cdks) are kinases that phosphorylate proteins involved in specific stages of the cell cycle

17

What are the advantages using Xenopus laevis as a biochemical model when looking at the cell cycle

Easy to collects its eggs, rapid division rate, large sized eggs makes protein purification easier and they can be manipulated by injection of RNA or chemicals into the oocytes

18

What is G0 phase

A quiescent, non-dividing phase

19

Pairing of homologues before segregation allows for crossing-over via homologous recombination, T or F

T

20

What are the stage of mitosis

Prophase, prometaphase, metaphase, anaphase and telophase

21

In meiosis I sister chromatids aren’t separated, what does happen during this stage

Homologous chromosomes pair up and crossing over takes place. These cells will be haploid with each homologue represented by two sister chromatids

22

What is cell-free mitosis

Technique that allows you to observe mitosis/nuclear division in a test tube outside of the cell membrane. This can be used to study changes i.e. in protein phosphorylation over time after cytoplasmic depletion using antibodies

23

What is meant by G­1 phase and what is going on the cell during this phase

G1 or gap 1 phase is the phase in which most cells are in. The cell is growing and constantly checking its environment. This growth is required to maintain cell size with subsequent divisions.

24

Levels of Cdk remain constant throughout the cell cycle, T or F

T

25

What happens during G2 phase of the cell cycle

More growth of the cell and environmental checking. It has a shorter duration than G1 phase

26

How can the ability of yeast to be haploid or diploid be harnessed to study the cell cycle

If you want to study a gene involved in cell cycle, manipulation will have a very deleterious effect on that organism. If you have carriers of the deleterious gene in diploid state and then switch the yeast to haploid when you want. Thus, diploids can be used to maintain lethal mutations that are then studied as haploids

27

During DNA duplication, each chromosome pair (maternal and paternal) is duplicated to give rise to sister chromatids, T or F

T

28

Sex chromosomes don’t cross over, T or F

F – they behave like homologues during sperm formation due to small regions of homology

29

What are the two purposes of homologous recombination between non-sister chromatids

Aligns the chromosomes ready for anaphase and facilitates formation of the synaptonemal complex as well as allowing for genetic recombination between paternal and maternal DNA on the same chromosome

30

Mistakes during meiosis I result in gametes with an extra chromosome or lacking a homologue, what is the name given to this event

Nondisjunction