Mitosis and Meiosis- Lecture 40

Question 1

What occurs in the S phase of the cell cycle?

Answer 1

DNA synthesis (will have greater than 2N and less than 4N DNA content)

Question 2

What distinguishes the G1 from the G2 phase?

Answer 2

G1 cells have 2N DNA content

G2 cells have 4N DNA content

Question 3

What are the steps of mitosis?

Answer 3

G2 (one cell)
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
G1 (two cells)

Question 4

Describe what happens in prophase.

Answer 4

centrosomes or microtubule organizing centers duplicated in S move to poles
nuclear membrane breaks down
chromosomes condense

Question 5

Describe what happens in prometaphase.

Answer 5

spindle fibers form

Question 6

What are the types of spindle fibers.

Answer 6

astral microtubules
kinetochore microtubules
polar microtubules

Question 7

Describe what happens in metaphase.

Answer 7

alignment of chromosomes in the center of mitotic spindle

Question 8

When is karyotyping typically done?

Answer 8

during metaphase

Question 9

Describe what happens in anaphase.

Answer 9

sister chromatids separate and move to opposite poles

cells elongate

Question 10

Describe what happens in telophase.

Answer 10

nuclear membrane re-forms
chromosomes decondense
spindle disappears

Question 11

Describe what happens in cytokinesis.

Answer 11

separation of daughter cells driven by actin filaments

Question 12

What makes germ cells distinct?

Answer 12

they have a 1N DNA content and are haploid

Question 13

Describe the events of meiosis I.

Answer 13

pairing and segregation of homologues –> daughter cells containing one maternal copy or one paternal copy (but not both)

Question 14

Describe the events of meiosis II.

Answer 14

pairing and segregation of sister chromatids (as in mitosis)

Question 15

During _____, _____ occurs in which segments of homologous chromosomes exchange genetic material.

Answer 15

Meiosis I

chromosomal crossing-over (recombination)

Question 16

_____ is a well-defined cellular structure that facilitates recombination.

Answer 16

The synaptonemal complex

Question 17

Describe the composition of the synaptonemal complex.

Answer 17

highly ordered

2 lateral elements and a central element

Question 18

What are the remnants of the synaptonemal complex?

Answer 18

chiasma
sites of crossing over that persist into metaphase of meiosis I
hold homologues together until segregation (like centromeres for sister chromatids)

Question 19

Describe the pairing of sex chromosomes in men during Meiosis I.

Answer 19

small regions of homology between X and Y chromosomes allow for pairing until segregation is ready to occur but the genes they could exchange are non-coding

Question 20

____ happens when homologues fail to separate in Meiosis I.

Answer 20

Non-disjunction