1.6 S Phase and Mitosis

Question 1

Before mitosis can proceed, DNA must be [ ].

Answer 1

replicated

Question 2

It is important that the genome be replicated only [ ] per cell cycle.

Answer 2

once

Question 3

In eukaryotes, DNA replication begins at multiple [ ], which are distributed throughout the genome.

Answer 3

origins of replication

Question 4

For DNA replication to begin, the DNA must first be [ ] at the OR by [ ].

Answer 4

1. unwound
2. helicase enzymes

Question 5

• Either late in mitosis or in early G1, DNA is bound by [ ] at each OR.
• This is called [ ] of ORs.
• DNA replicaion is only permitted at ORs preloaded with [ ].

Answer 5

1. two inactive Mcm helicases
2. “licensing”
3. Mcm helicase

Question 6

In S Phase, [ ] activates Mcm helicases.

Answer 6

S-cdk

Question 7

Mcm will only occur when [ ].

Answer 7

new inactive Mcm helicases are loaded in late mitosis or G1.

Question 8

The OR is bound by the [ ].

Answer 8

origin recognition complex (ORC)

Question 9

In late mitosis or early G1, [ ] and [ ] work together to recruit Mcm helicase to the ORC.

Answer 9

1. Cdc6
2. Ctd1

Question 10

With the help of [ ], S-Cdk activates Mcm helicase, leading to [ ] and binding of [ ].

Answer 10

1. accessory proteins
2. unwinding of DNA
3. replication machinery

Question 11

In late mitosis, [ ] promotes inactivation of Cdks.

Answer 11

APC/C

Question 12

Following APC/C, [ ] and [ ] are inactivated (dephosphorylated). This allows for McM helicase to [ ].

Answer 12

1. ORC
2. Cdc6
3. reload

Question 13

Genome replication requires [ ].

Answer 13

chromatin replication

Question 14

The production of chromatin proteins also increases during [ ].

Answer 14

S phase

Question 15

S-Cdks promote the synthesis of [ ] which ultimately become a histone octamer known as the [ ].

Answer 15

1. the four histone subunits
2. nucleosome

Question 16

Chromatin structure around the newly synthesized DNA must [ ].

Answer 16

match that of the original chromosome

Question 17

Newly replicated “chromosomes” remain [ ] to the original chromosome, known as [ ].

Answer 17

sister chromatids

Question 18

What are cohesins?

Answer 18

a large protein that forms a ring around the sister chromatids, and is reponsible for linking them together

Question 19

[ ] is a complex of 4 subunits. Two subunits from from the [ ] family of proteins. The other two subunits ([ ] and [ ]) complete the tetramer.

Answer 19

1. Cohesin
2. SMC
3. Scc1
4. Scc3

Question 20

M phase of the cell cycle begins with [ ]. In this process, sister chromatids will be divided into [ ], becoming separate chromosomes in the process.

Answer 20

1. mitosis
2. two daughter nuclei

Question 21

What are the five stages of mitosis?

Answer 21

prophase, prometaphase, metaphase, anaphase, and telophase

Question 22

In prohphase, sister chromatids [ ] inside the nucleus. Outside of the nucleus, the [ ] forms between two centrosomes.

Answer 22

1. condense
2. mitotic spindles

Question 23

In prometaphase, the [ ] breaks down. This allows [ ] to attach to the [ ].

Answer 23

1. nuclear envelope
2. chromatids
3. mitotic spindle, and initiate movement

Question 24

During metaphase, sister chromatids haev now aligned at the [ ].

Answer 24

spindle equator

Question 25

In anaphase, the chromatids are pulled towards their [ ], becoming [ ]. Both the microtubules get [ ], and [ ] move apart.

Answer 25

1. spindle poles 2. daughter chromosomes 3. shorter 4. spindle poles

Question 26

In telophase, [ ] reach the spindle poles and [ ]. A new [ ] assembles around each set of daughter chromosomes. This is the end of [ ], and the beginning of [ ].

Answer 26

1. daughter chromosomes 2. decondense 3. nuclear envelope 4. mitosis 5. cytokinesis

Question 27

What are the two distinct regulatory periods in mitosis?

Answer 27

G2M transition and metaphase to anaphase transition

Question 28

G2/M transition is associated with an increase in [ ] activity.

Answer 28

M-Cdk

Question 29

When does M-Cdk activity activates?

Answer 29

early in mitotic events: prophase, prometaphase, and metaphase

Question 30

M-Cdk initiates [ ] associated with prophase. This prevents chromatids from becoming [ ].

Answer 30

1. the chromosome condensation 2. entangled during the stages that follow

Question 31

Chromosome condensation is in part facilitated by the protein complex [ ].

Answer 31

condensin

Question 32

Condensin also facilitates [ ]. This results in the chromatids becoming distinct, separable units.

Answer 32

sister chromatid resolution

Question 33

What is the structure of condensin?

Answer 33

a five-subunit complex that resembles the four-subunit cohesin complex

Question 34

How are condensin and the cohesin complex similar?

Answer 34

includes two coiled-coil subunits of the SMC family of proteins

Question 35

During G2/M transition, M-Cdk initiates the [ ] in prometaphase.

Answer 35

breakdown of the nuclear envelope

Question 36

M-Cdk phosphorylates proteins that lead to the [ ], and facilitate ites binding to sister chromatids.

Answer 36

formation of the mitotic spindle

Question 37

In mitotic spindle, [ ] reach out away from the pole of which they originate. [ ] are oriented towards their respective role.

Answer 37

1. plus-ends 2. minus-ends

Question 38

The plus ends of [ ] attach themselves to chromatids.

Answer 38

kinetochore microtubules

Question 39

The kinetochore microtubules attach to chromatids via [ ] proteins at the [ ] of the chromatids.

Answer 39

1. kinetochore 2. centrosome

Question 40

At each pole exists a complex called the [ ].

Answer 40

centrosome

Question 41

The centrosome surrounds a pair of [ ].

Answer 41

centrioles

Question 42

What are centrioles?

Answer 42

a cylindrical organelle composed primarily of tubulin. They are important for spindle organization and cytokinesis

Question 43

Each kinetochore binds many [ ] which crosslink with each other, forming bundles known as [ ].

Answer 43

1. microtubules 2. K-fibers

Question 44

Kinetochores are structured in a [ ] orientation. This decreases the likelihood that they will [ ].

Answer 44

1. back-to-back 2. attach to microtubules of the same spindle pole

Question 45

How does the cell detect a correct attachment?

Answer 45

tension, associated with bi-orientation. When properly attached, kinetochores are pulled in [ ].