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Biology 1001A > Cycle 2: Cell Cycle and Cell Division > Flashcards

Cycle 2: Cell Cycle and Cell Division Flashcards

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1
Q

Difference between prokaryotes and eukaryotes.

A

Prokaryotes:
- DNA is in nucleoid
- Replication occurs through binary fission

Eukaryotes
- DNA is in nucleus
- Replication through mitosis and meiosis

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2
Q

Binary Fission in prokaryotic cells.

A

1) Prokaryotic parent cell initiates replication
2) A copy of the cell’s DNA is created
3) Cell elongates and cross wall forms
4) Cross wall forms completely and daughter cells separate

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3
Q

Eukaryotic Cell Cycle

A

Mitosis: cell division of into 2 identical daughter cells

G1 phase: cell growth
S phase: synthesis phase which is DNA Replication
G2 phase: preparation for mitosis
Mitosis: the cell division phase consisting of prophase, metaphase, anaphase, telophase
and cytokinesis
G0 phase: cell growth phase

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4
Q

Mitosis

A

Interphase: DNA is copies
Prophase: chromosomes pair up
Metaphase: chromosomes line up at the equator
Anaphase: sister chromatids are pulled apart
Telophase and Cytokinesis: cell pinches in the middle and two identical daughter cells are produced

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5
Q

Why is cell division necessary?

A

1) Tissue Repair
2) Multi-Cellular Growth
3) Regeneration

Maintain high Surface Area : Volume
Larger cell = more volume = larger diffusion distance

At a large enough volume, SA cannot keep up with the demands of the cell
Must divide to survive! It’s also easier to transport materials!!

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6
Q

What are the Cell Cycle Checkpoints?

A

1) G1/S assesses for:
- Cell size and DNA damage
- Growth factor presence required to enter
synthesis (S stage)
2) G2/M assesses for:
- Proper chromosomal replication
- DNA damage
- Molecules required to enter mitosis
3) Mitotic Spindle assesses for:
- Attachment of spindles at kinetochores
- Chromosomes are lined up evenly on metaphase plate
- Mitigates aneuploidy (abnormal number of chromosomes)

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7
Q

What are positive regulators?

A

Positive Regulators: Induces cell cycle
- Cyclins: binds to CDK to form Cyclin-CDK complex
- CDK: phosphorylation cascade intermediate

CDK + Cyclin = phosphorylate the Cyclin-CDK complex

Then the active cyclin-CDK complex phosphorylate the target protein and then becomes an active target protein.

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8
Q

What are negative regulators?

A

Negative Regulators: halts cell cycle
- p53 (the guardian of the genome): detects damage & upregulates p21 transcription
- p21: binds to CDK to inhibit Cyclin-CDK complex

If the negative regulators are unable to repair, apoptosis - programmed cell death is initiated, and if repairs are done, cell cycle progresses

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9
Q

Sources of genetic variation in mitosis include:
A) Recombination
B) Random alignment of chromosomes in metaphase
C) Independent assortment
D) A & B
E) None of the above

A

E

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10
Q

Choose the statement that is correct about cell cycles:
A) Negative regulators stopping the cell cycle will not result apoptosis
B) Binary fission and mitosis both produce two daughter cells that are identical to their respective parent cell
C) Binary fission produces two daughter cells that are unique to the parent cell
D) DNA in the nucleus of a prokaryote is replicated before binary fission
E) Eukaryotes and prokaryotes have the same process relating to cell division

A

B

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11
Q

Imagine you look into a microscope and see a cell that is in the S phase of the cell cycle. Which of the following statements could be correct about the cell?

1) The cell is undergoing anaphase
2) The cell have passed the G2/M checkpoint
3) The cell is receiving signals to differentiate
4) The cell is replicating its DNA

A) 1, 2, and 3
B) 1 and 3
C) 2 and 4
D) 4 only
E) All of 1, 2, 3, and 4

A

D

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12
Q

One key idea from the lecture on cell cycling is that not all cells divide all the time. Which of the following statements correctly describes the conditions when a cell might be in G0?

A) Cells that enter G0 have different probabilities of re-entering the cell cycle, depending on what type of cell they are.
B) Cells enter G0 only if they have DNA damage.
C) Cells in G0 cannot function.
D) Cells in G0 most likely have high turnover rates (replicate often).

A

A

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13
Q

Which of the following incorrectly describes the function of a cell cycle checkpoint?
A) G1/S : checks for cell size, DNA damage, and growth factor needed for S phase
B) G2/M : confirms that nuclear membrane has dissolved, and that spindle poles have formed
C) M : ensures spindles have correctly attached and chromosomes have lined up evenly on metaphase plate
D) All of the above are correct descriptions

A

B

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14
Q

Which stage in the cell cycle diagram would end at a “checkpoint” mediated by p53?
A) 1, 2 & 3 only
B) 1 & 3 only
C) 2 & 4 only
D) 4 only
E) All of 1, 2, 3 and 4 are correct.

A

B

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15
Q

Which of the following can lead to increased cell division?
1. Loss of p53.
2. Loss of CDK.
3. Loss of p21.
4. Loss of cyclins.

A) 1, 2 and 3
B) 1 and 3
C) 2 and 4
D) 4 only
E) All of 1, 2, 3 and 4 are correct.

A

B

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16
Q

What role do cell cycle checkpoints play in the “inheritance of sameness”?

1) Checkpoints ensure that DNA polymerase does not read the wrong template strand
2) Checkpoints ensure that all kinetochores are attached to spindles before proceeding to anaphase
3) Checkpoints ensure that organelles are properly replicated
4) Checkpoints ensure that damage is repaired before DNA is replicated

A) 1, 2, and 3
B) 1 and 3
C)2 and 4
D) 4 only
E) All of 1, 2, 3, and 4

A

C

17
Q

How do you count chromosomes?

A
  • One chromosome = one centromere
  • Sister chromatids are identical (before recombination)
  • Homologous chromosomes are related, but not identical
18
Q

Meiosis

A

Cell division into 4 unique daughter cells

Meiosis I is Reductional
- Homologous chromosomes separate
- The number of chromosomes is halved (46 → 23)
- The cells produced are now haploid

Meiosis II is Equational
- Sister chromatids separate
- The number of chromosomes is unchanged (23 → 23)
- Similar to Mitosis

19
Q

Recombination

A
  • Swapping chromosome segments in prophase I of meiosis
  • Source of genetic variation
20
Q

Linked genes

A
  • Alleles on the same chromosome are more likely to end up together
  • The closer they are, the lower the chance recombination will separate them
21
Q

What are some sources of genetic variation?

A

1) Homologous Recombination
- Crossing over between sister chromatids (prophase I)
2) Independent Assortment
- Chromosomes segregate independent of one another (anaphase)
3) Random Alignment
- Chromosomes line up at metaphase plate randomly (metaphase)
4) Random Fertilization

22
Q

Mitosis vs Meiosis

A

Purpose in Mitosis: produce genetically identical daughter cells
Purpose in Meiosis: produce genetically distinct gametes

of cell divisions in Mitosis: 1
# of cel division in Meiosis: 2

Total # of daughter cells in Mitosis: 2
Total # of daughter cells in Meiosis: 4

Final ploidy in Mitosis: diploid (humans)
Final ploidy in Meiosis: haploid (humans)

Recombination in Mitosis: no
Recombination in Meiosis: yes

23
Q

What causes aneuploidy?

A

Nondisjunction Causes Aneuploidy

24
Q

Which of the following statements are CORRECT regarding meiosis and mitosis?
A) Meiosis results in four haploid daughter cells, while mitosis results in two diploid daughter cells.
B) Meiosis occurs in somatic cells, while mitosis occurs in gametes.
C) Meiosis involves only one round of cell division, while mitosis involves two rounds of cell division.
D) Meiosis is responsible for growth and tissue repair

A

A

25
Q

Which one of the following statements about metaphase in mitosis or meiosis is correct?
A) Homologous chromosomes are pulled to opposite poles in metaphase I of meiosis
B) Single chromosomes are lined at the the metaphase plate in metaphase of mitosis
C) Metaphase in mitosis is the same as metaphase I in meiosis
D) There are two stages of metaphase in mitosis
E) None of the statements are correct

A

B

26
Q

Which one of the following accurately describes the number of chromosomes in a human cell at various stages?
A) Germ cell -> 23, Gamete -> 23, Zygote -> 46
B) Germ cell -> 46, Gamete -> 23, Zygote -> 23
C) Germ cell -> 23, Gamete -> 23, Zygote -> 23
D) Germ cell -> 46, Gamete -> 23, Zygote -> 46
E) None of the above are correct

A

D

27
Q

Alleles A and B are separated by a very short distance on one homolog of Chromosome 1, while allele C is found on the other homolog. Assuming Meiosis occurs without nondisjunction, and no crossing over occurs, what is the likelihood a gamete will inherit all three alleles?
A) 100%
B) Less than 100% but greater than 75%.
C) Less than 75% but greater than 50%
D) Less than 50% but greater than 0%
E) 0%

A

E

28
Q

XYY syndrome is a genetic condition in which a male has an extra Y chromosome. Assuming the XYY karyotype resulted from a single error in chromosome partitioning, in which of the following stages of meiosis might the error have occurred?
1) Meiosis I in the mother
2) Meiosis I in the father
3) Meiosis II in the mother
4) Meiosis II in the father

A) 1, 2, and 3
B) 1 and 3
C) 2 and 4
D) 4 only
E) All of 1, 2, 3, and 4

A

D

29
Q

Which of the following statements are CORRECT regarding non-disjunction events?

A) A non-disjunction event in the 1st meiotic division will result in all gametes exhibiting aneuploidy.
B) Trisomy 21 occurs from a meiotic non-disjunction event.
C) A non-disjunction event in the 2nd meiotic division will result in 50% of the produced gametes having a normal amount of chromosomes.
D) Non-disjunction events occur due to a malfunction in prophase I or II.

A

A

Biology 1001A (9 decks)

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