Book 11- Cell division

Question 1

What is mitosis?

Answer 1

a cell divides to produce two genetically identical cells

Question 2

What is meiosis?

Answer 2

the production of sex cells/ gametes

Question 3

What is the difference between mitosis and meiosis?

Answer 3

1. ) mitosis produces 2 daughter cells whereas meiosis produces 4
2. ) meiosis produces haploid genetically different cells, mitosis produces diploid genetically identical cells
3. ) meiosis- 2 nuclear divisions, mitosis- 1 division

Question 4

What are the 3 parts of interphase?

Answer 4

G1- growth phase 1, increased protein and organelle synthesis
S phase- DNA replication occurs
G2- growth phase 2

Question 5

what are cancer cells?

Answer 5

cells that undergo repeated cell division

Question 6

What is a benign tumour and malignant?

Answer 6

benign doesn’t spread, malignant does

Question 7

What happens in interphase?

Answer 7

1. ) DNA replication occurs
2. ) Organelles are synthesised
3. ) increased protein synthesis occurs
4. ) increased rate of respiration to provide energy for other processes

Question 8

What happens in prophase?

Answer 8

1. ) chromosomes condense so they become shorter and thicker

2. ) nuclear envelope breaks down

Question 9

What happens in metaphase?

Answer 9

1. ) spindle fibres form
2. ) centromeres attach to spindle fibres
3. ) chromosomes move along the spindle fibres to the middle of the cell

Question 10

What happens in anaphase?

Answer 10

1. ) centromere splits
2. ) sister chromatids separate
3. ) sister chromatids pulled along spindle fibres to opposite poles of the cell

Question 11

What happens in telophase?

Answer 11

1. ) nuclei reform
2. ) DNA become chromatin
3. ) spindle fibres begin to break down
4. ) two genetically identical cells are formed

Question 12

Why is meiosis important?

Answer 12

1. ) produces sex cells which are haploid
2. ) during fertilisation the diploid number is restored
3. ) This ensures that the diploid number remains the same after every generation
4. )meiosis produces genetic variation in offspring which increases the chance of species survival if the environment changes adversely

Question 13

Explain crossing over

Answer 13

• bivalents form
• homologous chromosomes twist round each other
• the point of cross over is the chiasma
• a section of DNA with a block of alleles breaks off, swaps position and reattaches
• this creates new combinations