Cell Division

Question 1

What parallel cycles comprise the cell cycle?

Answer 1

1. Chromosome cycle

2. Cytoplasmic cycle

Question 2

What are the parts of the chromosome portion of the cell cycle?

Answer 2

DNA synthesis: duplication of chromosomes

Karyokinesis: separation of chromosomes into 2 nuclei (for daughter cells)

Question 3

What are the component parts of the cytoplasmic cycle?

Answer 3

Cell growth: cell doubles in size

Cytokinesis: division of the cell by mitosis into two daughter cells

Question 4

What are the two major stages of the cell cycle?

Answer 4

Interphase and mitosis

Question 5

What generally happens during interphase?

Answer 5

Cell increases in size and content and replicates genetic material.

Question 6

What are the stages of interphase and what happens in each?

Answer 6

1. Gap 1: Growth and protein synthesis
2. Synthesis: DNA synthesis/genome duplication. Autosomal cell goes from 2n–>4n
   Centrosome duplicated
3. Gap 2 (resting phase): RNA, tubulin, other proteins and energy required for mitosis synthesized in this phase

Question 7

What happens during mitosis?

Answer 7

Cell divides nucleus and cytoplasm, giving rise to two daughter cells.

Question 8

What provides molecular control of the cell cycle?

Answer 8

Cyclins: proteins that regulate activity of cyclin-dependent kinases

Question 9

What are the cyclins involved in the cell cycle, and which phases are each associated with?

Answer 9

Cyclins D and E: passage past restriction point to push G1 into Synthesis
Cyclin A: Synthesis to G2
Cyclin B: G2 to Mitosis

Question 10

What are the stages of mitosis?

Answer 10

1. Prophase
2. Prometaphase
3. Metaphase
4. Anaphase
5. Telophase
6. Cytokinesis

Question 11

What happens during prophase?

Answer 11

• Chromosomes condense
• Kinetochores assemble on centromeres
• Centrosomes (MTOCs) migrate to poles
• Spindle begins to form

Question 12

What happens during prometaphase?

Answer 12

• Nuclear envelope breaks down
• Microtubules attach to kinetochores
• Chromosomes begin to migrate

Question 13

What happens during metaphase?

Answer 13

Chromosomes maximally condensed and lined up on metaphase plate.

Question 14

What happens during anaphase?

Answer 14

• Sister chromatids separate

- Cleavage furrow begins to form at late anaphase

Question 15

What happens during telophase?

Answer 15

• Spindle microtubules begin to depolymerize
• Nuclear envelope forms around daughter nuclei
• Chromosomes begin to decondense and nuclei form
• Cleavage furrow deepens

Question 16

What happens during cytokinesis?

Answer 16

Cell divides

Question 17

What do an increase in the number of mitotic figures and diversity of nuclear morphology signal?

Answer 17

Malignant cancer

Question 18

How do anti-cancer drugs work?

Answer 18

1. Disrupt mitotic spindle formation (can’t go through cell division without spindles)
2. Inhibit DNA synthesis (deprive cell of all material it needs to divide)

Question 19

How is meiosis different from mitosis?

Answer 19

Meiosis is 2 rounds of cell division WITHOUT intervening round of chromosome duplication; results in 4 heterozygous daughter cells with 1/2 as much chromosomal material.

Question 20

What are the stages of Meiosis I?

Answer 20

Prophase 1
Metaphase 1
Anaphase 1
Telophase 1

Question 21

What are the stages of Meiosis II?

Answer 21

Prophase 2
Metaphase 2
Anaphase 2
Telophase 2

Question 22

What are the stages of meiotic prophase I?

Answer 22

1. Leptotene: chromosomal condensation
2. Zygotene: homologous chromosomes pair up through formation of synaptonemal complex forming a tetrad or bivalent
3. Pachytene: chromosomes condense; chiasmata form as random exchange of genetic material occurs between homologous chromosomes
4. Diplotene: chromosomes condense to reveal ciasmata; areas of decondensation allow RNA synthesis
5. Diakinesis: chromosomes at max condensation; nucleolus and nuclear envelope disappear.

Question 23

What are the 4 types of centromere placement?

Answer 23

1. Metacentric (middle)
2. Submetacentric (slightly off center)
3. Acrocentric (long: short arms)
4. Telocentric (abnormal: only 2 arms with centromere at end)

Question 24

How does Down’s Syndrome develop?

Answer 24

Trisomy 21: extra chromosome at 21

Question 25

What are double minute chromosomes?

Answer 25

Fragments of chromosomal material that break off, form circular plasmids that can self-replicate.

• harbor extra copies of oncogenes and genes involved in drug resistance
• manifestation of gene amplification during tumor development
• replicate in nucleus of cell during cell division

Question 26

What stain allows us to see chromosome banding?

Answer 26

Giemsa stain allows us to view unique banding patterns of chromosomes - can see organization of genes in each chromosome.

Question 27

What happens in chronic myelogenous leukemia?

Answer 27

DNA from chromosome 9 and 22 gets swapped. Results in abnormal 22, which controls cell division: presents as missing regulatory domain so that signaling domain goes rampant–>wild replication in bone marrow.