Mitosis and Meiosis

Question 1

What are the different stages in the cell cycle?

Answer 1

Mitosis, G1, S, G2

Question 2

What occurs during G1?

Answer 2

Grows and organelles replicate

Question 3

What happens during S phase?

Answer 3

Replication of DNA. Synthesise

Question 4

Why do some cells exit the cell cycle?

Answer 4

Differentiate and become specialised

Question 5

Where are the different checkpoints during the cell cycle?

Answer 5

• G1/2, makes sure cells are at a certain size, DNA is undamaged before replication
• G2/M, chromosomes aligh, engage to spindle fibres

Question 6

What two organelles change during cell division?

Answer 6

Centriole - get 2. Nucleus.

Question 7

What charge do the DNA and histone proteins have?

Answer 7

DNA - negative. Histone Proteins - positive

Question 8

How many base pairs are there per nucleosome?

Answer 8

140

Question 9

What are the different folds of DNA>

Answer 9

• 3 fold to organise
• Then fold to 6 known as a solenoid
• Compacted into looped domains
• Forms chromatin
• Folds to form chromatid

Question 10

What is a chromosome?

Answer 10

Two chromatids held by a centromere

Question 11

What is Giemsa staining?

Answer 11

Binds to region of DNA. Shows each chromosome has a distinctive banding pattern

Question 12

What are Karyotypes?

Answer 12

Number and appearance of chromosomes in the nucleus of a cell

Question 13

What can Karyotypes help determine?

Answer 13

Anomalies. eg down syndrome, fragile X and turner syndrome

Question 14

What is meant by Metacentric?

Answer 14

Centromere location is the middle

Question 15

What is meant by Subametacentric?

Answer 15

Centromere location is between the middle and the end

Question 16

What is meant by Acrocentric?

Answer 16

Centromere location is close to the end

Question 17

What is meant by Telocentric?

Answer 17

Centromere location is at the end

Question 18

What happens during Prophase?

Answer 18

Chromosomes coil and condense. Centrioles divide - start to move towards to poles.

Question 19

What happens during Prometaphase?

Answer 19

See the chromosomes. Centrioles reach the poles. Spindle fibres form.

Question 20

What happens during Metaphase?

Answer 20

Centromeres align on metaphase plate. Engaged to spindle fibres. Kinetochore - pull apart the two sister chromatids

Question 21

What happens during Anaphase?

Answer 21

Centromeres splits. Chromosomes migrate to oppositie poles.

Question 22

What happens during Telophase?

Answer 22

Chromosomes at poles. Cytokinesis commences.

Question 23

What happens during Meiosis?

Answer 23

Homologous chromosomes find each other. Form a tetrad. Line up at metaphase plate

Question 24

What are the different stages of Prophase 1?

Answer 24

1. Leptonema.
2. Zygonema
3. Pachynema
4. Diplonema
5. Diakinesis

Question 25

What is Leptonema?

Answer 25

Homologous chromsomes search to find a pair

Question 26

What is Zygonema?

Answer 26

They have found each other, chromosomes condense, form a synaptonemal complex, bring together homologous pairs

Question 27

What is Pachynema?

Answer 27

Synapsis, chromosomes close together, call it packing in

Question 28

What is Diplonema?

Answer 28

Chiasma, try to pull apaprt but chromosomes remain intertwined, can’t really see this

Question 29

What is Diakinesis?

Answer 29

Centromere attachment, spindle fibres form

Question 30

What is Crossing Over?

Answer 30

Exchange genetic material

Question 31

What are the sources of genetic diversity during Meiosis?

Answer 31

Crossing Over. Random alignment.