Cell Division: Meiosis and Mitosis

Question 1

What is the cell cycle?

Answer 1

The cell cycle refers to a sequence of events that duplicates cells contents and divides the cell into two

Question 2

What are the cell cycle phases?

Answer 2

Interphase

M phase

Question 3

Describe the interphase

Answer 3

The interphase is split into 3 phases;
G1: growth
S: DNA synthesis
G2: Growth and preparation

Question 4

Describe the M phase

Answer 4

The M phase is where mitosis and cytokinesis occur

Question 5

Why is there a checkpoint between G1 and S

Answer 5

A signal is needed for the cell cycle to continue

Question 6

Describe cytokinesis

Answer 6

cytoplasmic division - it marks the end of mitosis as it ‘cuts’ the cell in two. The cytoplasm is divided in two by a contractile ring of actin and myosin filaments,

Question 7

When is the DNA packed loosely?

Answer 7

During interphase to allow DNA replication and RNA translation

Question 8

When is the DNA packed tightly?

Answer 8

During mitosis

Question 9

Describe mitosis

Answer 9

Only occurs in somatic cells
Produces two daughter cells
Daughter cells are genetically identical
Enables increase in cell number for tissue growth or repair

Question 10

What are the four stages or mitosis

Answer 10

Prophase: replicated chromosomes condense.The nuclear envelop begins to breakdown.
Metaphase: kinetochores microtubules attach sister chromatids to opposite poles of spindle.
Anaphase: Two daughter chromosomes form
Telophase: New nuclear envelope reassembles around each set, completing the formation of two nuclei and marking the end of mitosis.

Question 11

Describe Meiosis

Answer 11

Meiosis is split into: meiosis I and II. Meiosis is required for sexual reproduction 
Reduces ploidy (number of sets of chromosomes) -> from diploid to haploid
For production of gametes (eggs and sperm) from germ cells and it produced 4 haploid cells.

Question 12

Describe prophase 1:

Answer 12

In prophase 1, ‘cross over’ occurs where the DNA is shared. Increases genetic variation among daughter cells

Question 13

Describe Meiosis 1

Answer 13

Reduces ploidy
Homologous chromosomes exchange genetic info
Homologous chromosomes are separated

Question 14

Describe Meiosis 2

Answer 14

Seperation of sister chromatids

4 haploid cells (different) are produced

Question 15

Explain some key differences between meiosis and mitosis

Answer 15

Mitosis = 2 identical daughter cells
Cell number of for tissue repair
Only occurs in somatic
Meiosis = produces gametes, occurs in germ cells of gonads
Diploid to haploid
Fusion of egg and sperm at fertilization restores number of chromosome sets to 2