3.2.2 - Mitosis and Cell Cycle

Question 1

What are the 4 stages of mitosis?

Answer 1

Prophase

Metaphase

Anaphase

Telophase (cytokinesis)

Question 2

What does the diagram show?

Answer 2

Anaphase

Question 3

Cancer is caused by uncontrolled mitosis. How do most cancer drugs work?

Answer 3

1. Preventing DNA replication/
2. Inhibiting metaphase stage of mitosis by interfering with spindle formation.

Question 4

What happens during prophase?

Answer 4

• chromosomes condense (get short and fat)
• nuclear membrane breaks down
• centrioles move to opposite poles

Question 5

What does the diagram show?

Answer 5

Telophase (leading to cytokinesis)

Question 6

Describe the process of bacterial binary fission

Answer 6

• circular loop of dna replicates
• move to opposite ends of cell
• plasmids replicate
• cytoplams divides to = 2 identical daughter cells
• each has single copy of circular dna

Question 7

What does the diagram show?

Answer 7

Metaphase

Question 8

When would mitosis not result in 2 identical daughter cells?

Answer 8

If there was a mutation (very rare)

Question 9

Gametes (eggs and sperm) are haploid cells. What is meant by this?

Answer 9

They contain only 1 set of unparied chromosomes.

Question 10

What is mitosis important for?

Answer 10

• Growth
• Repair of damaged cells.
• Reproduction (single celled organisms)

Question 11

Describe what happens when a virus replicates.

Answer 11

• attachment protein binds to complementary receptor protein on host
• attachment protein specific to host receptor protein
• viruses inject genetic material
• hijacks host cells - uses host cells machinery/organelles
• to reproduce new viruses

Question 12

What happens during metaphase?

Answer 12

• double chromosomes line up on equator
• spindle forms
• spindle attaches to centromere

Question 13

What is the product of mitosis?

Answer 13

2 daughter cells that have the same number of chromosomes as the parent cell and each other.

Question 14

What does the diagram show?

Answer 14

Prophase

Question 15

The regular cycle of division separated by periods of cell growth is called…

Answer 15

the cell cycle

Question 16

How much of a single cell cycle is spent in interphase?

Answer 16

approximately 90%

Question 17

Bacterial cells replicate in a similar way to mitosis. What do we call their method of replication?

Answer 17

Binary Fission

Question 18

The rate of mitosis is controlled by…

Answer 18

1. The environment of the cell
2. ‘Growth factors’.
3. Two genes.

Question 19

What happens during telophase?

Answer 19

• nuclear membrane reforms
• cytokinesis (cytoplams divides)

Question 20

What are the 3 stages of the cell cycle?

Answer 20

Interphase

Nuclear division

Division of cyctoplasm (cytokinesis)

Question 21

How can we remember the order of the stages of mitosis?

Answer 21

• Prophase - (Preparation - condensing and spindle formation)
• Metaphase - (Middle - chromosomes lined up along middle of cell)
• Anaphase - (Action - chromatids pulled apart)
• Telophase - (Two - two new cells after division)

Question 22

How long does a mammalian cell to undergo 1 complete cell cycle?

Answer 22

24 hours

Question 23

What happens during anaphase?

Answer 23

• centromeres split
• chromatids pulled to opposite poles

Question 24

When a chromosome (DNA) replicates, the new stand is initially joined to the old at a place called the…

Answer 24

centromere.

Question 25

What are the advantages of reproducing via mitosis?

Answer 25

Only 1 parent required. Beneficial qualities are more likely to be passed on to offspring.

Question 26

A zygote is a **_diploid_** cell. What is meant by this?

Answer 26

A cell containing 2 complete sets of chromosomes (one from each parent)

Question 27

What are the disadvantages of reproducing by mitosis?

Answer 27

Less variation in offspring. Reduced ability to adapt to changing environment.

Question 28

What does the diagram show?

Answer 28

Interphase

Question 29

Describe a cell that is in **_interphase_**

Answer 29

Cell is actively synthesising proteins DNA replication Chromosomes are invisible

Question 30

why do you take cells from the root tip when studying mitosis?

Answer 30

Region where mitosis/cell division occurs;

Question 31

When when studying mitosis do you firmly squash the root tip?

Answer 31

To allow light through / make tissue layer thin;

Question 32

A cell under goes mitosis, the first division takes 24 hours and each subsequent one takes 8hours, how many cells are there after 3 days?

Answer 32

128

Question 33

How can you tell a cell has just under gone DNA replication?

Answer 33

Chromosomes are visiable as X shaped structures - 2 sister chromatids joined by a centromere

Question 34

During a root tip experiment why do we use the first 5mm of the root tip?

Answer 34

where the cells are under going mitosis

Question 35

during a root tip experiment why do we press firmly down on the cover slip?

Answer 35

make it single layer of cells SO light can pass through

Question 36

when counting cells during a root tip experiment - how can we be sure the mitotic index we calculate is accurate?

Answer 36

Look at many cells to ensure it is representative

Question 37

when growing bacteria, equipment must be sterile before use - suggest a way of sterilising equipment and why this is important?

Answer 37

boil in water/autoclave/wash in disinfectant to kill bateria thay may contaminate

Question 38

give two pieces of evidence of a cell that is undergoing mitosis? EXPLAIN your answer

Answer 38

- formation of sister chromatids BECAUSE DNA has replicated - individual chromosomes visible BECAUSE condensed

Question 39

a dark stain is used on chromosomes and binds more to some areas of the chromosomes than others, giving the chromosomes a striped appearance. suggest ways in which the structure of the chromosome could differ along its length to result in the stain binding more in some areas?

Answer 39

- difference in base sequence - difference in histones - difference in condensation

Question 40

how would you calculate the percentage of cells in which chromosomes are visible and would consist of a pair of chromatids together?

Answer 40

- find no. of cells in prophase and metaphase & ADD together - divide by total - x by 100

Question 41

in an investigation, a different set of results were obtained when the count was repeated on another occasion with a different garlic root tip. give 2 reasons for the difference in results?

Answer 41

- genetic differences - different day