Notes 18

Question 1

The cell cycle

Answer 1

Is an ordered set of events that divides a cell into 2 daughter cells

Question 2

Cell cycle 2 main phases

Answer 2

Interphase & Mphase

Question 3

Interphase

Answer 3

the stage in development of 2 divisions

Question 4

G1

Answer 4

First intermediate gap stage in which the cell grows and prepares for DNA replication

Question 5

S phase

Answer 5

Synthesis stage in which DNA is replicated

Question 6

G2

Answer 6

Second intermediate gap stage in which the cell finishes growing and prepares for cell division

Question 7

M phase

Answer 7

The period of the cell cycle in which the cell and contents divide to create two genetically identical daughter cells

Question 8

Mitosis

Answer 8

nuclear division, where DNA (as condensed chromosomes) is separated into two identical nuclei

Question 9

Cytokinesis

Answer 9

Cytoplasmic division, whereby cellular contents are segregated and the cell splits into two

Question 10

Processes of Interphase

Answer 10

DNA replication – DNA is copied during the S phase of interphase

Organelle duplication – Organelles must be duplicated for twin daughter cells

Cell growth – Cytoplasmic volume must increase prior to division

Transcription / translation – Key proteins and enzymes must be synthesised

Obtain nutrients – Vital cellular materials must be present before division

Respiration (cellular) – ATP production is needed to drive the division process
(DOCTOR)

Question 11

how do chromosomes condense

Answer 11

By supercoiling during mitosis

Question 12

Chromosome

Answer 12

DNA is temporarily packaged into a tightly wound and condensed chromosome prior to division and is inaccessible to transcriptional machinery (during mitosis)

Question 13

Chromatin

Answer 13

DNA is usually loosely packed within the nucleus as unravelled chromatin and is DNA is accessible to transcriptional machinery (during interphse)

Question 14

Centromere

Answer 14

Hold together genetically identical strands called sister chromatids

Question 15

Mitosis

Answer 15

the process of nuclear division, whereby duplicated DNA molecules are arranged into two separate nuclei

Question 16

Before mitosis

Answer 16

Interphase- DNA is present as uncondensed chromatin, a clearly defined nucleus
Centrosomes and other organelles have been duplicated, Cell is enlarged in preparation for division

Question 17

stages of mitosis

Answer 17

Prophase
Metaphase
Anaphase
Telophase

Question 18

Prophase

Answer 18

-DNA supercoils and chromosomes condense
-Chromosomes are made of genetically identical sister chromatids (joined at a centromere)
-Paired centrosomes move to the opposite poles of the cell and form microtubule spindle fibres

Question 19

Metaphase

Answer 19

-Microtubule spindle fibres from both centrosomes connect to the centromere of each chromosome
-Microtubule depolymerisation causes spindle fibres to shorten in length and contract
-This causes chromosomes to align along the centre of the cell (equatorial plane or metaphase plate)

Question 20

anaphase

Answer 20

-Continued contraction of the spindle fibres causes genetically identical sister chromatids to separate
-Once the chromatids separate, they are each considered an individual chromosome in their own right
-The genetically identical chromosomes move to the opposite poles of the cell

Question 21

telophase

Answer 21

-Once the two chromosome sets arrive at the poles, spindle fibres dissolve
-Chromosomes decondense (no longer visible under light microscope)
-Nuclear membranes reform around each chromosome set
-Cytokinesis occurs concurrently, splitting the cell into two

Question 22

Prometaphase

Answer 22

-The nuclear membrane breaks down and the nucleus dissolves
-Chromosomes captured

Question 23

Cytokinesis

Answer 23

final stage of mitosis, the process of cytoplasmic division, where the cell splits into two identical daughter cells

Question 24

cytokinesis overview

Answer 24

reformation of interphase microtubules array contractile ring forms and forms a cleavage furrow

Question 25

what controls the progression of the cell cycle

Answer 25

cyclin (regulatory proteins)

Question 26

cyclin dependent kinases (CDKs)

Answer 26

control cell cycle processes through phosphorylation

Question 27

regulation of proteins in cell division

Answer 27

phosphorylation: adding Pi=active, remove Pi=inactive
gene expression: genes in nucleus match in protein that orders division
degradation of proteins: Ubiquitin labeled will destroy

Question 28

CDK are made of

Answer 28

A catalytic subunit and regulatory subunit

Question 29

when are cdks active

Answer 29

when bound to regulatory subunit

Question 30

Anaphase-promoting complex

Answer 30

adds ubiquitin tag to proteins to destroy once destroyed, protein is active and can chop up cohesion (holding sisters together)

Question 31

transcriptional cyclin regulation

Answer 31

ensure proper temporal expression of cyclins

Question 32

protein degradation cyclin regulation

Answer 32

restricts cyclin to appropriate cell cycle stage by proteosomes

Question 33

astral microtubules

Answer 33

interacts with cortex and orders spindals to axis of cell division

Question 34

kinetochore microtubules

Answer 34

attaches to kinetochore on sister pair and transports chromosomes to poles

Question 35

polar microtubules

Answer 35

attach each spindle pole to opposite side and maintain structure

Question 36

kinetochore

Answer 36

multilayer protein structures on centromere
function: mediates attachment of chromosomes to kinetochore microtubules during metaphase

Question 37

Surveillance mechanism

Answer 37

(checkpoint pathways) motoring cell cycle to ensure the previous one is properly completed

Question 38

how do nuclear envelope reform

Answer 38

segments of ER associate with chromosomes and merge to produce envolope