Cell Divison, Diveristy, Differentiation

Question 1

What’s in interphase

Answer 1

G1
S
G2

Question 2

G0

Answer 2

Cell has left cell cycle:
To differentiate
Apoptosis
Senescence

Question 3

Senescence

Answer 3

Cells no longer divide

Question 4

Check points in cell cycle

Answer 4

At G1

At G2

Question 5

Why are there

checkpoints

Answer 5

To prevent
uncontrolled division
that would lead to
tumours
To detect and repair
damage to DNA

Question 6

M phase

Answer 6

Checkpoint chemical
triggers condensation
of chromatin
Cell growth stops
4 stages of mitosis
Cytokinesis
then occurs

Question 7

G1

Answer 7

Cells grow
Transcription of genes
to make RNA occurs
Synthesis of biological
molecules occur e.g.
protein synthesis

Question 8

S phase

Answer 8

DNA replicates
(doubles)
Each chromosome
has two sister
chromatids
Once the cell has
entered this phase, it
is committed to
completing the cell
cycle

Question 9

Why does S phase

happen very rapidly

Answer 9

Exposed DNA base
pairs are more
susceptible to
mutagens so this
phase happens
quickly to reduce the
chances of mutations

Question 10

G2

Answer 10

Cells grow
Chemicals stimulate
histones and
formation of the
spindle
Organelles duplicate

Question 11

Prophase

Answer 11

Chromosomes
condense- chromatids shorten, thicken and DNA supercoils
Centrioles duplicate and move to opposite
poles
Cytoskeleton protein (tubulin)threads form a spindle between centrioles.
Nuclear envelope
breaks down
Nucleolus no
longer visible

Question 12

Metaphase

Answer 12

Chromosomes align at
equator and attach by
their centromeres
Two sister chromatids
of each chromosome
are attached to
spindle fibres

Question 13

Anaphase

Answer 13

Centromere splits
Sister chromatids of a pair are pulled
towards opposite poles and directions of the cell by motor proteins walking along tubulin threads to spindle fibres
shortening (now
chromosomes)

Question 14

Telophase

Answer 14

Chromosomes
decondense
Spindle disappears
Nuclear envelope
reforms and a
nucleolus reappears
cells contain two nuclei each genetically identical to one an other

Question 15

Cytokinesis in an

animal cell

Answer 15

plasma membrane folds inwards
the middle of the cell
pinches inwards,
creating an
indentation called the
cleavage furrow

Question 16

Cytokinesis in a

plant cell

Answer 16

The cell plate forms
down the middle of
the cell, creating a
new wall that
partitions it in two

Question 17

Where does mitosis

occur in plants

Answer 17

Roots

Shoots

Question 18

Haploid

Answer 18

Having only one set of

chromosomes

Question 19

Homologous

Answer 19

Matching
chromosomes,
containing the same
genes at the same
places (loci)
May contain different
alleles for some of the
genes

Question 20

Diploid

Answer 20

Having two complete
sets of chromosomes
(found as pairs)

Question 22

Maternal homologues

Answer 22

These chromosomes
will have the same
genes as the maternal
homologue in the
chromosome pair

Question 23

Paternal homologues

Answer 23

These chromosomes
will have the same
genes as the paternal
homologue in the
chromosome pair

Question 24

Metaphase I

Answer 24

Homologue pairs line
up at the metaphase
plate
The orientation of
pairs is random

Question 25

Anaphase I

Answer 25

Homologues separate
to the opposite ends
of the cell
Sister chromatids
stay together

Question 26

Telophase

Answer 26

``` Newly forming cells at haploid Each chromosome has 2 non-identical sister chromatids ```

Question 27

Prophase Il

Answer 27

Chromosomes condense Spindle fires begin to capture.

Question 28

Metaphase Il

Answer 28

Chromosomes line up individually along the equator

Question 29

Anaphase Il

Answer 29

``` Independent segregation of sister chromatids to opposite ends of the cell ```

Question 30

Telophase Il

Answer 30

``` New forming gametes are haploid Each chromosome has just one chromatid ```

Question 33

Prophase I

Answer 33

``` Starting cell is diploid Homologous chromosomes pair up and exchange fragments (crossing over of non-sister chromatids) ```