Cell Cycle and Cell Division

Question 1

What is a haploid cell in humans?

Answer 1

n
23 chromosomes
Gametes

Question 2

What is a diploid cell in humans?

Answer 2

2n
23 Chromosome pairs
Somatic (body) cell

Question 3

What are the stages in the cell cycle?

Answer 3

Interphase- a period of synthesis and growth
Mitosis- Formation of two genetically identical nuclei
Cytokineses- Division of cytoplasm to form two daughter cells

Question 4

What are the stages in interphase?

Answer 4

G1 phase - growth and normal metabolic roles
S phase - DNA replication
G2 phase - growth and preparation for mitosis by organelle replication

Question 5

What is the order of the stages in mitosis?

Answer 5

Prophase
Metaphase
Anaphase
Telophase

Question 6

What’s the structure of a chromosome in prophase?

Answer 6

Two chromosomes joined at centromere with sister chromatids opposite each other

Question 7

What occurs in interphase?

Answer 7

• high metabolic activity
• requires ATP
• cell increases in size
• DNA and organelles replicate

Question 8

What occurs in prophase?

Answer 8

• chromosomes condense
• centrioles divide and move to opposite poles
• nuclear envelope disappears
• spindle forms

Question 9

What occurs in metaphase?

Answer 9

• chromosomes line up on equator

- spindle fibres attach to centromere

Question 10

What occurs in anaphase?

Answer 10

• spindle fibres shorten
• centromeres divide
• sister chromatids separate
• each is pulled to opposite side of the cell

Question 11

What occurs in telophase?

Answer 11

• chromosomes uncoil and lengthen
• spindle breaks down
• nuclear envelope reforms
• nuclear division is complete

Question 12

How does the spindle differ in plant and animal cells?

Answer 12

In animal cells the spindle degenerates at telophase

In plant cells the spindle remains throughout new cell wall formation

Question 13

Where does mitosis occur in plant and animal cells?

Answer 13

Animal cells:
Epithelia, bone marrow, gut lining

Plant cells:
Meristems

Question 14

How does cytokineses occur in animal cells?

Answer 14

The construction of the parent cell creates a cleavage furrow dividing the cell from the outside inwards

Question 15

How does cytokineses occur in plant cells?

Answer 15

Droplets of cell wall material form a cell plate across the equator from the inside outwards to extend and join to create a new cell wall

Question 16

Where are centrioles found?

Answer 16

In animal cells but not plants

Question 17

Why does mitosis give genetic stability?

Answer 17

It maintains the chromosome number by producing genetically identical daughter cells

Question 18

How is mitosis used for growth?

Answer 18

It increases cell number and can also be used to repair tissue and replace dead cells

Question 19

What is asexual reproduction?

Answer 19

Produces genetically identical offspring

Takes place in unicellular organisms (yeast, bacteria) and some plants and tubers (strawberries)

Question 20

How can the cell cycle be affected?

Answer 20

By damage to the genes which control it

Through radiation, chemicals and viruses which may stop division or cause uncontrollable division

Question 21

What happens when cells divide uncontrollably?

Answer 21

Tumors such as cancers are formed

Question 22

How are tumours controlled?

Answer 22

Tumour suppressing genes

Question 23

What are proto-oncogenes and what do they become?

Answer 23

They are genes that have the potential to cause cancer and when they mutate they become oncogenes