Cell Cycle and Cell Division

Question 1

Mitosis

Answer 1

• Makes two daughter cells (almost identical to parent cell)

Question 2

Meiosis

Answer 2

• Daughter cells get half of the parent cell’s genetic information

Question 3

Interphase Phases

Answer 3

G1: Grows in preparation for cell division. 46 chromosomes are organized in tangled chromatin fibers
S: Each Chromatid is copied. Still 46 chromosomes but each chromosome has 2 sister chromatids joined at a centromere (92 chromatids todal)
G2: More growth prior to entering mitosis. Cell duplicates organelles.

Question 4

Chromatid

Answer 4

Single copy of the genetic material

Question 5

G0

Answer 5

Phase where cells live but don’t divide (example: some neurons)

Question 6

The 4 Phases of Mytosis

Answer 6

1. ) Prophase
2. ) Metaphase
3. ) Anaphase
4. ) Telophase

Question 7

Prophase

Answer 7

• Chromatin fibers condense and untangle into individual chromosomes (each with 2 sister chromatids)
• Centrosomes (each with 2 centrioles) are at opposite sides of the cell outside the nucleus –> Send out spindle fibers (microtubule proteins) to centromere of each chromosome –> align chromosomes in the exact middle between the two centrosomes

Question 8

Metaphase

Answer 8

1. ) Prometaphase:
   - Nuclear membrane & nucleolus disintegrate
2. ) Metaphase:
   - Chromosomes align along the metaphase plate
   - Spindle fibers continue to attach to a specific place (Kinetochore) on each centromere

Question 9

Anaphase

Answer 9

• Centrosomes pull the sister chromatids apart

- Sister chromatids move to opposite poles of the cell

Question 10

Telophase

Answer 10

• New nuclear envelope forms around each group of centrosome and the chromosomes
• Cytokinesis divides the cell into two cells

Question 11

Meiosis

Answer 11

• ## Formation of gametes (Haploid cells: 1 set of 23 chromosomes)

Question 12

Meiosis (Basics)

Answer 12

• Formation of gametes (Haploid cells: 1 set of 23 chromosomes)
• One parent cell with 46 chromosomes undergoes Two rounds of division to form Four daughter cells each with 23 chromosomes

Question 13

Haploid Cells

Answer 13

A cell that contains a single set of chromosomes (Ex. Human Gamete Cells)

Question 14

Meiosis Phases (Basics)

Answer 14

Meiosis I

• Prophase I
• Metaphase I
• Anaphase I
• Telophase I

Meiosis II

• Prophase II
• Metaphase II
• Anaphase II
• Telophase II

Question 15

Prophase I (5 Phases)

Answer 15

1. ) Leptotene: 46 chromosomes, each with 2 sister chromatids, condense + Nuclear membrane disintegrates
2. ) Zygotene: Each chromosomes binds (Synapsis) to its homologue
3. ) Pachytene
4. ) Diplotene
5. ) Diakinesis

Question 16

Prophase I (5 Phases)

Answer 16

1. ) Leptotene
2. ) Zygotene
3. ) Pachytene
4. ) Diplotene
5. ) Diakinesis

Question 17

Leptotene

Answer 17

• First phase of Prophase I of Meiosis
• 46 chromosomes, each with 2 sister chromatids, condense
• Nuclear membrane disintegrates

Question 18

Leptotene

Answer 18

• 1st phase of Prophase I of Meiosis I
• 46 chromosomes, each with 2 sister chromatids, condense
• Nuclear membrane disintegrates

Question 19

Zygotene

Answer 19

• 2nd phase of Prophase I of Meiosis I
• Synapsis occures: each chromosomes binds to its homologue
• Each pair of homologous chromosomes pair with each other loosely (this structure is called a Tetrad)

Question 20

Pachytene

Answer 20

• 3rd phase of Prophase I of Meiosis I
• Crossover event: Exchange of genetic material between Homologous chromosomes (where and how often this occurs is random) which produces additional genetic variation

Question 21

Diplotene

Answer 21

• 4th phase of Prophase I of Meiosis I
• Homologous chromosomes uncoil and begin to pull away (remain attached at Chiasmata: where the exchange of genes in a crossover event took place)

Question 22

Diakinesis

Answer 22

• 5th phase of Phrophase I of Meiosis I

- Homologous chromosomes remain connected in at least one of the Chiasmata

Question 23

Metaphase I

Answer 23

• Tetrad go to the Metaphase Plate at the center of the cell

Question 24

Anaphase I

Answer 24

• Tetrads split up and homologous chromosomes are pulled to opposite poles

Question 25

Telophase I

Answer 25

• Cytokenesis occurs and produces two haploid daughter cells (which will undergo additional division in Meiosis II)

Question 26

What happens following Meiosis I?

Answer 26

• There is another Interphase with G1 phase, S phase (except in this S phase the chromosomes don’t get replicated!), and G2 phase
• The cell is then ready for Meiosis II

Question 27

How does Meiosis II progress?

Answer 27

Exactly like mitosis! :D

The only difference is that Meiosis produces 4 haploid daughter cells with 23 chromosomes each

Question 28

Labile Cells

Answer 28

• Cells that never enter G0, rapidly progress through the cell cycle, and replicate fast
• Examples: Skins cells, Bone Marrow stem cells, gut epithelial cells

Question 29

Stable Cells

Answer 29

• Cells in G0 that can re-enter G1 to divide when needed or when stimulated
• Examples: Liver cells, Lymphocytes in the blood, and Smooth Muscle cells

Question 30

Permanent Cells

Answer 30

• Cells that are always in G0 phase, post-mitotic cells

- Examples: Neurons in the brain, cardiac muscle cells

Question 31

G1 Checkpoint

Answer 31

• Checkpoint at the end of G1 where the cell checks to ensure that the right proteins have been synthesized in the correct amount and their is no cell damage
• If there is DNA damage, the cell tries to repair it in G0 or initiates Apoptosis

Question 32

G2 Checkpoint

Answer 32

• Checks for DNA damage

- If no DNA damage then the cell can enter Mitosis