Mitosis + Meiosis

Question 1

How many chromosomes do humans have?

Answer 1

46. 22 pairs of autosomes, 1 pair of sex chromosomes.

Question 2

What is the name given to a picture that depicts the number and appearance of chromosomes in a cell?

Answer 2

Karyotype

Question 3

What does a chromosome consist of?

Answer 3

Supercoiled DNA. Long arm (q) and short arm (p).

Question 4

Which process produces 2 identical daughter cells, genetically identical to the parent cell?

Answer 4

Mitosis

Question 5

What is mitosis for?

Answer 5

For growth and repair

Question 6

Give the names of supercoiled DNA at each stage of cell replication.

Answer 6

Before replication = chromatin
During replication = chromosomes
After replication = chromatids

Question 7

Which stage of the cell cycle does mitosis occur?

Answer 7

Interphase

Question 8

Name the stages of the cell cycle.

Answer 8

G1, S, G2

Question 9

What occurs in G1?

Answer 9

Rapid growth
New organelles are produced
Protein synthesis of proteins involved in spindle formation

Question 10

What occurs in the S phase?

Answer 10

DNA replication

Centrosome replication

Question 11

What occurs in G2?

Answer 11

Chromosomes condense

Mitochondria and centrioles double

Question 12

Name the 5 stages of mitosis.

Answer 12

Prophase, prometaphase, metaphase, anaphase, telophase

Question 13

What occurs in prophase?

Answer 13

1. Chromatin condenses into chromosomes.

2. Centrioles divide and form spindle fibres

Question 14

What occurs in prometaphase?

Answer 14

1. Nuclear membrane breaks down

2. Cell has no nucleus

Question 15

What occurs in metaphase?

Answer 15

Chromosomes line up along equatorial plane

Question 16

What occurs in anaphase?

Answer 16

Sister chromatids separate to opposite poles of the cell = disjunction

Question 17

What occurs in telophase?

Answer 17

1. Nuclear membrane reforms

2. Cytokinesis begins

Question 18

Name a condition caused by non-disjunction.

Answer 18

Downs syndrome. Non-disjunction at chromosome 21, results in trisomy.

Question 19

List the differences between mitosis and meiosis.

Answer 19

1. Meiosis is only in gametes, mitosis is in all other cells
2. Meiosis has two cell divisions
3. Meiosis produces 4 haploid cells, mitosis produces 2 diploid cells
4. Daughter cells are genetically different to parent cells in meiosis
5. Meiosis is not a cycle

Question 20

Briefly outline meiosis 1.

Answer 20

Chromosome number is halved.

Prophase 1: Crossing over occurs between non-sister chromatids. Results in genetic diversity.

Metaphase 1: Random assortment on metaphase plate. Results in genetic diversity.

Question 21

Briefly outline meiosis 2.

Answer 21

Sister chromatids separate. Haploid cells are produced.

Question 22

What is mitosis of germ cells called?

Answer 22

Gametogenesis

Question 23

What are the steps of gametogenesis in males?

Answer 23

Primordial germ cells > lots of mitosis > spermatogonia

Question 24

When does gametogenesis occur in males?

Answer 24

Puberty. Continues throughout life.

Question 25

What are the steps of gametogenesis in females?

Answer 25

Primordial germ cell > 30 mitoses > Oogonia

Question 26

When does gametogenesis occur in females?

Answer 26

Oogonia enter prophase 1 in utero. Process is suspended until ovulation. Meiosis 1 is completed at ovulation. Meiosis 2 is only completed if fertilisation occurs.

Question 27

What is the term given to the event when precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines?

Answer 27

Gonadal mosaicism. One cell line is normal, the other is mutated.

Question 28

Which sex is gonadal mosaicism more common?

Answer 28

Males

Question 29

What are the implications of gonadal mosaicism?

Answer 29

Parent is healthy as only germline is affected. Foetus may have genetic diseases.