Cell division, diversity and organisation

Question 1

What is the order of the different sections (Gaps) of interphase in the cell cycle?

Answer 1

Gap 0 (waiting/resting), Gap 1, Synthesis (DNA replication and cell growth), Gap 2 (preparation for mitosis)

Question 2

What are checkpoints in the cell cycle?

Answer 2

Processes that prevent the next stage of the cell cycle from being started unless the processes of the previous stage have occurred correctly.

Question 3

What are the 3 checkpoints in the cell cycle?

Answer 3

G1 checkpoint, G2 checkpoint and Metaphase checkpoint.

Question 4

Where is the G1 checkpoint and what does it do?

Answer 4

After Gap 1, before Synthesis, arrests cell if there is DNA damage.

Question 5

Where is the G2 checkpoint and what does it do?

Answer 5

After Synthesis, before Gap 2, arrests cell if DNA replication did not occur properly.

Question 6

Where is the Metaphase checkpoint and what does it do?

Answer 6

during Metaphase, arrests cells if chromosomes have not aligned at the mitotic plate and are under bipolar tension.

Question 7

What is the purpose of mitosis?

Answer 7

For growth, tissue repair and asexual reproduction.

Also: (clonal expansion of lymphocytes, production of new stem cells)

Question 8

What happens in prophase of mitosis?

Answer 8

The nuclear envelope breaks down and disappears.
DNA condenses and supercoils forming short, fat chromosomes.
Centrioles move to opposite poles.
Spindle fibres begin to form from the centrioles.

Question 9

What happens in metaphase of mitosis?

Answer 9

Centrioles arrive at opposite poles.
Spindle fibres attach to the centromere of chromosomes.
Chromosomes line up on the mitotic plate.
Metaphase checkpoint.

Question 10

What happens in anaphase of mitosis?

Answer 10

Spindle fibres begin to shorten, causing the two chromatids of each chromosome to separate at the centromere.
Sister chromatids are pulled towards opposite poles of the cell.

Question 11

What happens in telophase of mitosis?

Answer 11

Chromatids reach opposite poles.
Nuclear envelopes are reformed.
The cell begins cytokinesis, the cell membrane begins to pinch at the equator forming a cleavage furrow.

Question 12

What is the order of the different phases of mitosis?

Answer 12

PMAT

Question 13

What does mitosis produce?

Answer 13

2 genetically identical diploid daughter cells.

Question 14

What is the purpose of meiosis?

Answer 14

Produce 4 haploid gametes for sexual reproduction.

Meiosis is a reductive process.

Question 15

What does meiosis produce?

Answer 15

4 genetically different haploid daughter gametes.

Question 16

How is P1 of meiosis different from prophase in mitosis?

Answer 16

Homologous chromosomes form bivalents.

Crossing over occurs.

Question 17

How is M1 different in meiosis different from metaphase in mitosis?

Answer 17

Bivalents become aligned along the equator of the cell in independent assortment.

Question 18

How is A1 in meiosis different from anaphase in mitosis?

Answer 18

Homologous chromosomes move to opposite poles of the cell.

Chromosomes are NOT split at the centromere.

Question 19

How is T1 in meiosis different from telophase in mitosis?

Answer 19

The centrioles duplicate.

Question 20

How is genetic variation produced in sexual reproduction?

Answer 20

Crossing over and independent assortment during meiosis.

Reduction and fusion of gametes.

Question 21

What is crossing over and when does it happen?

Answer 21

Happens during P1 of meiosis.
Non-sister chromatids (but homologous) cross over forming a chiasma (where they cross over). This results in recombinant DNA.

Question 22

What is independent assortment and when does it occur?

Answer 22

Happens during M1 and M2 of meiosis.

The arrangement of each bivalent is random, so each of the daughter nuclei get a mix of paternal and maternal alleles.

Question 23

What is the reduction and fusion of gametes?

Answer 23

One haploid gamete will fuse with another haploid gamete to form a diploid zygote with 50% different alleles from any one of the original parents.

Question 24

How are squamous epithelial cells specialised?

Answer 24

Very thin (squamous) => allows rapid diffusion.
Secretes basement membrane => attaches squamous epithelial cells to connective tissue.

Question 25

How are ciliated epithelial cells specialised?

Answer 25

Cilia on surface => beat in unison to sweep mucus away from the lungs/move ovum in the oviduct.

Question 26

How are erythrocytes specialised?

Answer 26

Biconcave shape => increases SA:V ratio.
No nuclei and few organelles => more haemoglobin can be carried.
Flexible => squeeze through narrow capillaries.

Question 27

How are neutrophils specialised?

Answer 27

Multi-lobed nucleus => squeeze through small gaps to get to the site of infection.
Granular cytoplasm with many lysosomes => contains enzymes used when attacking pathogens.

Question 28

How are sperm cells specialised?

Answer 28

Flagellum => capable of movement towards the ovum.
Many mitochondria => supply the energy required by the flagella.
Haploid => form a diploid cell at fertilisation.
Acrosome => contains digestive enzymes to get through the protective layers around the ovum.

Question 29

How are palisade cells specialised?

Answer 29

Chloroplasts => can move to absorb more light and produce more glucose.
Rectangular shape => can be closely packed forming a continuous layer.

Question 30

How are root hair cells specialised?

Answer 30

Long extension => increases the SA of the cell to maximise water and mineral uptake.

Question 31

How are guard cells specialised?

Answer 31

Thicker on one side => change shape when they lose water, closing the stomata.

Question 32

Describe the levels of cellular organisation.

Answer 32

Cell - Tissue - Organ - Organ system.

Question 33

What is a tissue?

Answer 33

A collection of similar cells performing a common function.

Question 34

What is an organ?

Answer 34

A collection of tissues working together to perform a specialised function.

Question 35

What is an organ system?

Answer 35

A collection of organs working together to perform an overall life function.

Question 36

What are stem cells?

Answer 36

Undifferentiated cells, capable of mitosis, able to differentiate and become specialised.

Question 37

Where are some examples of where stem cells are found?

Answer 37

Bone marrow, meristem of plants.

Question 38

What is the difference between embryonic and adult stem cells?

Answer 38

Embryonic stem cells are totipotent (can become any other type of cell).
Adult stem cells are pluripotent/multipotent.

Question 39

What is cell differentiation?

Answer 39

Changes that occur in cells of a multicellular organism so that each different type of cell becomes specialised to perform a specific function.

Question 40

What changes during cell differentiation?

Answer 40

The amount of different organelles.
The shape of the cell.
The contents of the cell.

Question 41

What are merismatic cells?

Answer 41

Simple, undifferentiated cells within merismatic tissue (cambium) in plants. They can divide and differentiate into the cells required for the xylem and phloem.

Question 42

What are the potential uses of stem cells in research and medicine?

Answer 42

Research into developmental biology.

Repair of damaged tissues, treatment of neurological conditions such as Alzheimer’s and Parkinson’s.