Module 2 Section: 6 - Cell division

Question 1

What are the 3 phases of interphase?
2 phases of mitosis and explain what happens?

Answer 1

Interphase:
- growth phase 1
- synthesis
- growth phase 2
Mitotic phase:
- mitosis= nucleus divides
- cytokinesis= cytoplasm divides & 2 daughter cells produced

Question 2

What is G0? Why might a cell enter G0?

Answer 2

The resting phase, in which the cell leaves the cycle temporarily or permanently
When a cell is specialized it no longer needs to divide, hence entering G0

Question 3

Which cells DON’T divide?

Answer 3

DNA damaged cells and senescent cells

Question 4

What happens at each checkpoint of the cell cycle? (3)

Answer 4

G1 checkpoint checks for:
cell size, nutrients, growth factors, DNA damage

G2 checkpoint checks for:
cell size, DNA replication, DNA error

Spindle assembly checkpoint checks for:
all chromosomes attached to spindles and being aligned

Question 5

What happens at G1 phase?

Answer 5

• proteins synthesised
• organelles replicated
• cell enlarges

Question 6

What happens at synthesis phase?

Answer 6

• DNA replicated

Question 7

What happens at G2 phase?

Answer 7

• energy stores are increased
• DNA checked for errors
• cell enlarges

Question 8

what are the uses of mitosis

Answer 8

-growth
-repair
-asexual reproduction
-Production of new stem cells

Question 9

what are the 4 division stages of mitosis in order

Answer 9

-prophase
-metaphase
-anaphase
-telophase

Question 10

what happens in prophase

Answer 10

-chromosomes condense and become visible
-nuclear envelope breaks down
-nucleolus disappears
-centrioles move to opposite poles and release spindle fibres

Question 11

what are the parts of the chromosomes called and where are they in the chromosome

Answer 11

• the separate strands are called chromatids
  -the middle part that joins the strands together is called the centromere

Question 12

what happens in metaphase

Answer 12

-chromosomes line up on the metaphase plate (equator)
-spindle fibres attach to centromere

Question 13

what happens during the anaphase

Answer 13

-centromeres divide separating each pair of sister chromatids
-spindle fibres contract pulling the chromatids to opposite poles

Question 14

what happens during telophase

Answer 14

-chromosomes begin to grow and become longer and thinner
-spindle fibres begin to disintegrate
-nucleus reforms
-cytoplasm splits(cytokinesis)

Question 15

what does meiosis produce

Answer 15

gametes

Question 16

what are all the stages of meiosis and in order

Answer 16

-prophase I
-Metaphase I
-Anaphase I
-Telophase I
-Prophase II
-Metaphase II
-Anaphase II
-Telophase II

Question 17

what happens in Prophase I

Answer 17

-Chromosomes condense and become visible as sister chromatids
-nuclear envelope breaks down
-nucleolus disintegrates
-Homologous Chromosomes pair up and crossing over occurs
-Centrioles migrate to opposite poles and start to make spindle fibres

Question 18

what are homologous chromosomes

Answer 18

are pairs of chromosomes that have the same genes but possibly different versions (called alleles) of those genes.

Question 19

what is crossing over

Answer 19

where homologous chromosomes (the ones from your mother and father) swap some of their genetic material. This creates new combinations of genes.

Question 20

What happens during crossing over in meiosis?

Answer 20

During crossing over, homologous chromosomes (chromosomes from both parents) line up next to each other in prophase I of meiosis. They exchange genetic material by swapping sections of their chromatids. This creates new combinations of genes, leading to genetic variation in offspring.

Question 21

what happens in meta phase I

Answer 21

-Homologous Chromosomes align at the metaphase plate
-Independent assortment occurs
-spindle fibres attach to sister chromatid centromere

Question 22

what is independent assortment

Answer 22

how chromosomes are randomly distributed to gametes

Question 23

what is the process of independent assortment (answer from marksheet)

Answer 23

-(homologous
chromosomes) line up,
across the centre of the cell
on the equator / on the
metaphase plate
- maternal or paternal
chromosomes / either one
of the homologous pair,
can end up, facing either
pole / in either (daughter) cell

Question 24

what is a sister chromatid

Answer 24

two identical copies of a single chromosome formed during DNA replication

Question 25

what is the Chiasmata

Answer 25

point where crossing over occurs

Question 26

what occurs in anaphase I

Answer 26

Spindle fibre contract and Homologous Chromosomes separate and move to opposite sides of the cell

Question 27

What happens in Telophase I

Answer 27

-nuclear envelope reforms -spindle fibres breakdown -cytokinesis

Question 28

What happens in Prophase II

Answer 28

-nuclear envelope breaks down -Chromosomes condense and become visible -Centrioles move to opposite poles and release spindle fibres

Question 29

what happens in metaphase II

Answer 29

-Chromosomes line up on the metaphase plate -Spindle fibres attach to the centromeres

Question 30

what happens in anaphase II

Answer 30

-Spindle fibres attach back to centromere causing the centromere to divide and chromatids to go to each pole

Question 31

what happens in telophase II

Answer 31

-Chromosomes start to grow and become longer and thinner -spindle fibres begin to disintegrate -Cytoplasm reforms

Question 32

what 2 events in meiosis lead to genetic variation

Answer 32

-crossing over and Independent assortment

Question 33

what are senescent cells

Answer 33

cells that have stopped dividing and have reached a stage of permanent growth but don't die

Question 34

what is a stem cell

Answer 34

undifferentiated cells which have the potential to differentiate into a range of specialised cell types

Question 35

what do stem cells in bone marrow differentiate into

Answer 35

blood cells

Question 36

What do stem cells in the meristem differentiate into

Answer 36

xylem and phloem

Question 37

How could stem cells cure Alzheimer's

Answer 37

as with Alzheimer's nerve cells in the brain die causing memory loss, researchers are hoping to use stem cells to regrow healthy nerves

Question 38

How could stem cells cure Parkinson's

Answer 38

as people with Parkinson's suffer from tremors they cannot control and the disease causes the loss of a particular type of nerve cell that releases dopamine and stem cells could help regenerate dopamine-producing cells

Question 39

what is the structure and function of neutrophils

Answer 39

f: a type of white blood cell that defends the body against disease s: flexible shape to engulf foreign particles, many lysosomes to break down engulfed particles

Question 40

what is the structure and function of erythrocytes

Answer 40

f: red blood cells that carry oxygen in the blood s: biconcave disc provides large surface area, no nucleus so more space for haemoglobin,

Question 41

what is the structure and function of epithelial cells

Answer 41

f: cover the surfaces of organs s:cilated epithelia have Cilia to beat particles away, squamous epithelia are thin for short diffusion pathway

Question 42

what is the structure and function of sperm cells

Answer 42

f: to fertilise the egg s: have flagellum to swim to the egg, lots of mitochondria to provide it with energy, acrosome has digestive enzymes to allow it to penetrate the surface of the egg

Question 43

what is the structure and function of palisade mesophyll cells

Answer 43

f: carry out most of photosynthesis s: many chloroplasts , thin walls for short diffusion pathway of co2

Question 44

what is the structure and function of root hair cells

Answer 44

f: absorb water and mineral ions from the soil s: large surface area for absorption, thin cell wall for entry of water and ions, cytoplasm has extra mitochondria for energy for active transport

Question 45

where are embryonic stem cells found and what do they differentiate into

Answer 45

in the inner embryo, any type of cells

Question 46

what is totipotent cells

Answer 46

totipotent cells can develop into any cell type, including extra-embryonic tissues;

Question 47

what is Pluripotent cells

Answer 47

Pluripotent cells can form almost all cell types but cannot form extra-embryonic tissues;

Question 48

what is Multipotent cells

Answer 48

Multipotent cells can give rise to a limited range of related cell types.

Question 49

Suggest three ways in which the use of embryonic stem cells in research has practical benefits to biological knowledge.

Answer 49

(can be grown into different tissues to) test how effective new medicinal drugs are (1) (can be grown into different tissues to) test for side effects / toxicity of new drugs (1) (can be grown and) studied to see how they develop into different cell types (developmental research) (1) cell function can be studied to find out what can make it fail to work properly in certain (named) diseases