Lecture 2 - Mitosis and Meiosis

Question 1

Know the main differences between prokaryotes, eukaryotes, and viruses.

L2 S7-10

Answer 1

Slides 7-10 in lecture 2 cover this information

Question 2

Diploid cells have:

L2 S14/15

A. Two chromosomes
B. Two sets of chromosomes
C. One set of chromosomes
D. Two pairs of homologous chromosomes

Answer 2

B. Two sets of chromosomes

Question 3

What is a centromere?

L2 S16

Answer 3

A region on the DNA that contains a specialized, highly repetitive sequences that allow proteins to attach to the chromosome and connect them to microtubules for mitosis/meiosis.

Question 4

What is a telomere?

L2 S16

Answer 4

A region on the DNA that contains a specialized, highly repetitive sequences that protect the ends of DNA from degradation from enzymes present in cells that target DNA for degradation

Question 5

What is an origin of replication?

L2 S16

Answer 5

Regions on the DNA that contain a specialized that allows for the replication complex to open the double helix and bind to the DNA so replication may occur.

Question 6

What are the different classifications of centromere location?

L2 S18

Answer 6

Submetacentric:
-centromere is positioned slightly off center so that on arm is slightly longer than the other

Metacentric:
-centromere is positioned in the center

Telocentric:
-centromere is positioned so close to the end that a short arm is not visible by light microscopy

Acrocentric:
-centromere is positioned near the end and a short arm is present

Question 7

What is the sequence of events in the cell cycle, including checkpoints, beginning after cell division? (name the steps in mitosis as well)

L2 S20

Answer 7

Interphase:

• G1
• G1/S checkpoint
• S
• G2
• G2/M checkpoint

M phase (mitosis):

• prophase
• prometaphase
• metaphase
• anaphase
• telophase

Cytokinesis

Question 8

What is G0?

L2 S20;26

Answer 8

A non-dividing phase that cells enter when they have matured. The cells may leave this phase if division is needed later.

Question 9

What occurs in the different steps of M phase?

Answer 9

Prophase:

• chromosomes condense
• mitotic spindle forms

Prometaphase:

• nuclear envelope disintegrates
• spindle microtubules anchor to kinetochore

Metaphase:

• chromosomes align on metaphase plate
• spindle-assembly checkpoint occurs

Anaphase:
-sister chromatids separate and migrate towards poles

Telophase:

• nuclear envelope begins to form around chromosomes again
• chromosomes begin to decondense

Question 10

Relate number of chromosomes to number of DNA molecules in the different phases of the cell cycle.

(Chromosome #/# of DNA molecules)

L2 S28

Answer 10

G1: (23/23)

S: (23/23->46)

G2: (23/46)

Prophase/prometaphase: (23/46)

Metaphase: (23/46)

Anaphase: (46/46)

Telophase/cytokinesis: (23/23)

Question 11

Which is the correct order of stages in the cell cycle?

L2 S29/30

A. G1, S, prophase, metaphase, anaphase
B. S, G1, prophase, metaphase, anaphase
C. Prophase, S, G1, metaphase, anaphase
D. S, G1, anaphase, prophase, metaphase

Answer 11

A. G1, S, prophase, metaphase, anaphase

Question 12

When does crossing over occur?

L2 S37

Answer 12

Prophase I

Question 13

What occurs in the different steps of meiosis?

L2 S35

Answer 13

Meiosis I:

• homologous chromosomes are separated; resultant cells are 2n
• crossing over occurs

Meiosis II:
-sister chromatids are separated; resultant cells are 1n