Module 1 Checkpoints and Mitosis

Question 1

___ occurs Before S phase

Primary point at which a cell must choose whether or not to divide.

Checks for ___, ___, ___, or ___

Is environment favorable? yes, enter S phase

Answer 1

G1 Checkpoint

Cell size
Availability of nutrients
DNA Damage
Replication errors

Question 2

___ checks that cells have all requirements for division

Checks again for DNA damage and if replication has been completed

Should there be damages or errors, it remains in the stage for repair or death.

All good? Enter mitosis

Answer 2

G2 checkpoint

Question 3

____ occurs in metaphase

Checks if chromosomes are properly attached to the ___

If yes, pull duplicated chromosomes apart

Answer 3

M checkpoint/spindle checkpoint

mitotic spindle

Question 4

Mitosis starts at the culmination point of ___(___)

It is a short period of ___, ___, and ___.

Answer 4

interphase (G2 phase)

Chromosome condensation
segregation
cytoplasmic division

Question 4

Mitosis is also importabnt for replacement of cells lost to ___(___), wear and tear and for wound healing in soem organisms, regeneration of body parts.

Answer 4

natural friction (attrition)

Question 5

Stages of mitosis (5)

Answer 5

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

Question 6

In ___ the appearance of ___ marks the first phase of mitosis. The cell becomes spheroid, more refractile and viscous

Answer 6

Prophase

thin-thread like condensing chromosome

Question 7

Each prophase chromosome is composed of ___, the chromatids, which are the result of the replication of DNA during ___ phase.

Answer 7

two coiled filaments

S

Question 8

Each prophase chromosome is composed of ___, the chromatids, which are the result of the replication of DNA during ___ phase.

Answer 8

two coiled filaments

S

Question 9

During prophase, chromatids become ___ and ___. Two sister chromatids of each chromosome are held together by the special DNA-containing region, called the ___ or ___. This is from the ___ proteins - the binding sites of microtubules.

Answer 9

shorter and thicker

centromere/primary constriction

kinetochore

Question 10

During prophase, chromosomes approach the ___ leaving the ___ empty.

The spindle or mitotic apparatus forms in the ___.

Two pairs of ___, surrounded by ___ which are microtubules migrate to opposite poles of the cell, and between it is the spindle.

Answer 10

nuclear envelope
central space of the nucleus

cytoplasm

centrioles
aster

Question 11

Types of fibers in the Mitotic spindle (3)

Answer 11

Polar fibers - extend from two poles of the spindle to the equator

Kinetochore fibers - attach to the kinetochores of centromeres and extend toward the poles

Astral fibers - radiate outward from the poles to the periphery or cortex of cell

Question 12

At the last part of prophase the ___ gradually disintegrates. And the disappearance of the __ marks the end of it.

This is with the exception of some primitive plants and animals

Answer 12

Nucleolus

Nuclear envelope

Question 13

The ___ is characterized by a period of frantic activity where the spindple appears to be trying to ___ and ___ the chromosomes.

A form of “tug-of-war”

The sister chromatids become attached to opposite poles through their kinetochores.

Bipolar forces hold chromosomes on the metaphase plate

Answer 13

Prometaphase

contain
align

Question 14

During ___, the chromosomes are ___ and ___.
The centromeres occupy the plane of the equator of the mitotic apparatus (equatorial/metaphase plate)

The sister chromatids are held together by the ___ and the ___ of the two sister chromatids face opposite poles. This would permit proper ___ in the next phase.

The cells pause until all chromosomes are lined up appropriately.

Answer 14

Metaphase

Shortest
Thickest

centromere
kinetochores

separation

Question 15

At metaphase, subunits (___) are added to the plus end of a microtubule at the kinetochore and are removed from the minus end at the spindle pole.

This is what causes the poleward flux of tubulin subunits and microtubules remain under tension.

Answer 15

tubulin dimers

Question 16

____ begins abruptly with the synchronous ___ of each chromosome into its sister chromatids called ___. Each with one ___.

This is due to increase in ___ accumulating at spindle poles. Membrane vesicles release ___ ions to initiate the phase.

Answer 16

Anaphase
Splitting
Daughter chromosomes

CA2+
calcium

Question 17

Steps of Anaphase (2)

Answer 17

Anaphase A
poleward movement of chromatids due to shortening of kinetochore microtubules. Centromeres and kinetochores remain foremost

Anaphase B
Separation of poles themselves and elongation of polar microtubules
Astral microtubules can also help with attractive interaction with cell cortex

Question 18

The ___ starts with the reorganization of two new ____ and their entry into the ___ of interphase. A ___ reassembles around each group of chromosomes to form two ___.

The mitotic apparatus, except the centrioles disappear.

RNA synthesis restarts causing nucleolus to reappear.

Answer 18

Telophase

nuclei
G1

Nuclear envelope
daughter nuclei