Mitosis and meiosis

Question 1

Schwann theory on mitosis

Answer 1

Cells come from cells

Question 2

Virchow theory on mitosis

Answer 2

Cells arise through binary fission

Question 3

Stages of mitosis

Answer 3

Prophase - metaphase - anaphase - telophase - cytokinesis

Question 4

What happens in early prophase?

Answer 4

Condensing replicated chromosomes

Question 5

What happens in late prophase?

Answer 5

Prometaphase
Microtubules emerge from centrosome at poles of mitotic spindle extend into nuclear region reaching chromosomes. Some of the spindle microtubules attach to kinetochores. Other spindle microtubules make contact with microtubules coming from opposite pole

Question 6

What happens in metaphase?

Answer 6

Mitotic spindle is fully formed. Chromosomes midway between spindle poles

Question 7

What happens in anaphase?

Answer 7

Two centromeres of each chromosome come apart, separating the sister chromatids. Proteins of kinetochores, powered by ATP, walk newly separated daughter chromosomes along microtubules towards opposite poles of the cell. Microtubules attached to kinetochores shorten. Spindle microtubules not attach lengthen. Poles move farther apart

Question 8

What happens in S phase?

Answer 8

Interphase - each chromosome is duplicated by the cell

Question 9

How many chromosomes are there after DNA synthesis?

Answer 9

46 chromosomes - 92 chromatids

Question 10

Characteristics of mitosis

Answer 10

• Genetically identical cells
• Diploid cells
• Takes place throughout an organism’s lifetime
• Involved in asexual reproduction

Question 11

Characteristics of meiosis

Answer 11

• Genetically unique cells
• Haploid cells
• Sexual reproduction
• 4 haploid cells produced

Question 12

What happens during meiosis?

Answer 12

• Interphase: DNA replication
• Prophase 1: chromosomes join
• Metaphase 1: homologs align in centre of cell
• Anaphase 1: homologous chromosomes separated
• Anaphase 2: sister chromatids separate

Question 13

What holds homologous chromosomes together?

Answer 13

Synaptonemal complex

Question 14

Where does crossing over occur?

Answer 14

Between homologous chromosomes

Non-sister chromatids of homologous ch

Question 15

Characterics of spermatozoa

Answer 15

23 chromosomes, n=1

Question 16

What is an egg?

Answer 16

A secondary oocyte in metaphase ii

Question 17

N number of zygote

Answer 17

2

Question 18

How many primary coccyges in ovary?

Answer 18

300,000

Question 19

What is produced by meiosis in males?

Answer 19

Spermatozoa

Question 20

How are secondary spermatocytes produced?

Answer 20

Spermatogonium undergoes mitosis twice to produce primary spermocyte (meiosis i) and then secondary spermatocyte (meiosis ii)

Question 21

What is a germ cell?

Answer 21

Any cell that gives rise to gametes

Question 22

What is a primordial germ cell?

Answer 22

Diploid cells that arise through mitosis. Arise in primitive streak and migrate via the gut of an embryo to the developing gonads. Once in gonads, they form oogonium (female fetus). At 7 months, oogonia turn into primary oocytes. In males, oogonium = spermatogonia

Question 23

What does ss mean?

Answer 23

Chromosome made from one chromatid

Question 24

What does ds mean?

Answer 24

Chromosome made from two chromatids

Question 25

True or false, germ cells can only undergo meiosis

Answer 25

False

Question 26

True or false, meiosis is only completed in females once the oocyte is fertilised?

Answer 26

True

Question 27

Do males run out of primary oocytes?

Answer 27

No