Cell division

Question 1

Human cells are diverse….

Answer 1

Sperm cell, SMooth muscle cell, Red blood cell, Nerve cell, epthelial cell

Question 2

A cell has three possible destinies:

Answer 2

Live and function without dividing
* grow and divide
* die

Various signals tell a cell which path to take
Homeostasis is maintained when there is balance
between cell proliferation and cell death

Question 3

The cell theory states that..

Answer 3

all organisms are made of cells and all cells come from pre-existing cells

Question 4

Somatic cell division

Answer 4

Mitosis –diploid (2n) to diploid (2n)

Question 5

Reproductive cell division

Answer 5

Meiosis -diploid (2n) to haploid (1n)

Question 6

Why do somatic cells divide?

Answer 6

Growth and development, tissue renewal.
Results in two daughter cells that are genetically and
functionally identical to the parent cell.

Question 7

Do all somatic cells divide?

Answer 7

Many, but not all, some a lot more than others!

Question 8

What are somatic cells doing most of the time?

Answer 8

Going about their functions, within interphase

Question 9

The eukaryotic cell cycle - Interphase

Answer 9

G1: Growth or Gap Phase 1
most cellular activities are occurring here
Duration variable – cell type specific

S: Synthesis of DNA
DNA replication occurs strands are separated at the
hydrogen bonds holding the nucleotides together new
strand of DNA is synthesized opposite each of the old
strands.

G2 : Growth or Gap Phase 2
checks for correct DNA synthesis prepares for the Mitotic
Phase (synthesis of the proteins and enzymes required,
gathering of reactants), replication of centrosomes is
completed
The eukaryotic cell cycle - Interphase
Objective
One

Question 10

Most nerve cells are in..

Answer 10

G0

Question 11

Mitotic phase =

Answer 11

mitosis + cytokinesis

Prophase Early Late

Metaphase

Anaphase Early Late

Telophase and
cytokinesis

In some textbooks you will see prometaphase (it is shown here as late prophase)

Question 12

Interphase mitosis

Answer 12

Uncondensed chromosomes

Question 13

Prophase mitosis

Answer 13

Early; two sister chromatids
Late- condensed chromoseoms + spindle tracks- fragments of nuclear enevlope

Question 14

Metaphase mitosis

Answer 14

condensed chromosomes align at equator

Question 15

anaphase mitosis

Answer 15

seprated chromosomes

Question 16

telophase mitosis

Answer 16

nuclear enevlope forming
cleavage furrow

Question 17

What is a sister chromatid?

Answer 17

Human diploid cells have 46 chromosomes, 23 from each parent

During interphase, DNA replicates
Two identical chromatids per chromosome
These are called sister chromatids
During anaphase, sister chromatids separate
before the nuclear envelope reforms in
telophase
Daughter cells are “identical” to parent cell
During prophase, DNA condenses
During metaphase, chromosomes “line” up

Question 18

mitosis result

Answer 18

Result:
two daughter cells that are genetically identical to the parent cell

Question 19

mitotic cell cycle checkpoints

Answer 19

G1 check
M check
G2 check

Question 20

multiple signals are required to pass…

Answer 20

G1 & M checkpoint

Question 21

G1 checkpoints:

Answer 21

• Is the DNA undamaged?
• Is cell size and nutrition OK?
• Appropriate signals present?
  If not - may exit to G0

Question 22

M checkpoint

Answer 22

are all chromosomes
attached to spindles?

if not stop singal is received

Question 23

Meosis occurs in the..

Answer 23

gonads (ovaries and testes)

Question 24

Meosis produces gametes which are

Answer 24

haploid (a single set of 23 chromosomes

fertilisation then restores the diploid number of chromosomes (2n)
produces cells genetically different from the parent cell

Question 25

There are two stages of Meiosis

Answer 25

Mesosis I
Meosis II

Question 26

Meosis I

Answer 26

Prophase I (synapsis and crossing over, tetrads form)
Metaphase I (pairs of homologous chromosomes)
Anaphase I (sister chromatids remain attached)
Telophase I

Question 27

Meiosis I – separates homologous chromosomes

Answer 27

Synapsis: two sister chromatids
of each pair of homologous
chromosomes pair up

The 4 chromatids are called a
tetrad

Non-sister chromatids within
these tetrads may then cross
over: recombination

Question 28

Meiosis II – separates sister chromatid

Answer 28

very similar to
mitosis,
except not
preceded by DNA
replication

Question 29

Mitosis versus Meiosis

Answer 29

Mitosis- occurs in both haploid and diploid cells
Meosis- occurs only in diploid cells

Mitosis; DNA repication occurs in interpahse before mitosis begind

Meosis; Ocurrs during interphase before Meosis I but not meosis II

Number of divsions
Meosis: 2
Mitosis- 1

Synapsis of homologus chromosomes
Meosis- occurs in prophase I along with crossing over between non sister chromatids ; resulting chiasmata hold pairs together due to sister chromatid coehession
Mitosis; no

Number of daughter cells & genetic composition
Meosis- 4 haploid genetically diff from parent cells and eachother
Mitosis- 2 genetically identical to parent cells with same umber of chromsomes

Question 30

Sources of variation

Answer 30

Sources of genetic variation as a result of meiosis:
* independent assortment at metaphase I (223 >8 million possible combinations)
* crossing over at prophase 1 (~1-3 crossover events per pair)
* Fusion between two gametes (> 223 times 2 23 combinations!!