L2 Mitosis

Question 1

How does DNA normally exist in cells

Answer 1

decondensed, spread out

Question 2

What are the two forms of decondensed DNA

Answer 2

heterochromatin and euchromatin

Question 3

What is a chromosome

Answer 3

linear DNA molecule

Question 4

What is the centromere

Answer 4

region where the spindle attaches

Question 5

What are homologous chromosomes

Answer 5

same genes arranged in same order

Question 6

How are homologous chromosomes inherited

Answer 6

one from mother, one from father

Question 7

What are chromatids

Answer 7

newly copied DNA strands joined to each other by a centromere

Question 8

What is pulled apart

Answer 8

chromatids

Question 9

Describe prophase

Answer 9

condensation of sister chromatids

Question 10

Describe metaphase

Answer 10

attachment of mitotic spindle to kinetochore by microtubules

Question 11

Describe anaphase

Answer 11

separation of sister chromatids to opposite poles

Question 12

Describe telophase

Answer 12

nuclear envelope reassembly, start of cytokinesis

Question 13

Why is prophase important

Answer 13

gets chromosomes into the right form for mitosis

Question 14

During what phase can chromosomes get tangled

Answer 14

anaphase

Question 15

What checks chromosome tangling

Answer 15

decatenation check point

Question 16

What can chromosome tangling lead to

Answer 16

aneuploidy and chromosome rearrangements in daughter cells

Question 17

What is a genetic model for the cell cycle

Answer 17

yeast

Question 18

What are the advantages of yeast as a genetic model

Answer 18

rapid division, cell cycle control genes highly conserved, haploid or diploid

Question 19

What is a use of haploid and diploid yeast

Answer 19

diploids are used to maintain lethal mutations - then studied in haploids

Question 20

Why is yeast more flexible than mammalian cells

Answer 20

temperature sensitive mutations - allows growth at permissive temperature

Question 21

What is used as a biochemical model for the cell cycle

Answer 21

xenopus

Question 22

What are the advantages of xenopus as a biochemical model

Answer 22

easy to collect eggs, large size, rapid division, manipulated by injection

Question 23

What complex is degraded quickly part way through M phase

Answer 23

Cyclin B complex

Question 24

What drives the cell through M phase

Answer 24

M-Cdk

Question 25

What must M-Cdk trigger

Answer 25

mitotic spindle assembly, chromosome condensation, breakdown of nuclear envelope

Question 26

What is the effect of the inhibitory phosphate on the M-Cdk complex

Answer 26

keeps the protein complex inactive

Question 27

What removes the inhibitory phosphate from the M-Cdk complex

Answer 27

phosphatase Cdc25

Question 28

What activates phosphatase Cdc25

Answer 28

S-Cdk complexes

Question 29

What is the effect of removing the inhibitory phosphate from M-Cdk complex

Answer 29

activates the M-Cdk

Question 30

What is the effect of an active M-Cdk complex

Answer 30

positive feedback - build up of active M-Cdk complexes

Question 31

What is the effect of active M-Cdk complexes

Answer 31

rapid activation of mitosis

Question 32

What does APC stand for

Answer 32

anaphase promoting complex

Question 33

What is progression through metaphase/anaphase transition driven by

Answer 33

protein destruction

Question 34

What is loss of heterozygosity

Answer 34

cross chromosomal event that results in loss of the entire gene

Question 35

Name the three ways that loss of heterozygosity can be induced

Answer 35

non-disjunction, mitotic recombination, gene conversion

Question 36

Describe non-disjunction

Answer 36

wrong number of chromosomes

Question 37

What can cause non-disjunction

Answer 37

lagging chromosomes

Question 38

When can non-disjunction occur

Answer 38

anaphase

Question 39

What is central to separation of chromosomes

Answer 39

spindle

Question 40

What is the function of kinetochore microtubules

Answer 40

attach to chromosomes at the kinetochore

Question 41

What is the function of astral microtubules

Answer 41

position the spindle

Question 42

How does the cell detect incorrectly lined up kinetochores

Answer 42

low tension

Question 43

True or false - properly lined up kinetochores are unstable

Answer 43

false - stable - therefore higher tension

Question 44

What is the function of separase

Answer 44

destroy bridges between chromatids

Question 45

What is a problem if a cell is hemizygous

Answer 45

if the allele is mutant there is no normal copy of the gene

Question 46

What are the downstream consequences of no normal gene copy

Answer 46

no active proteins are made

Question 47

Describe mitotic recombination

Answer 47

DNA swaps between chromatin arms

Question 48

What can some mitotic recombinations cause

Answer 48

two mutant alleles on one set of chromatids

Question 49

What enzyme causes gene conversion

Answer 49

DNA polymerase

Question 50

Describe gene conversion

Answer 50

DNA polymerase jumps between 2 DNA molecules, replicates another allele