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BIO 101 > Topic 7 - Cell Reproduction > Flashcards

Topic 7 - Cell Reproduction Flashcards

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1
Q

What are the functions of cell division?

A
  • Reproduction, growth, and repair
  • Distributes identical sets of chromosomes to daughter cells
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2
Q

Prokaryotic cell division

A
  • Binary fission
  • No nucleus
  • Single circular chromosome
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3
Q

What do eukaryotic chromosomes look like?

A
  • Multiple, linear chromosomes contained in nuclear envelope, which makes cell division more complex
  • Many organisms have pairs of chromosomes called homologous chromosomes (chromosomes of the same morphology with genes in the same location)
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4
Q

How are mitotic chromosomes condensed?

A
  1. Nucleosome: subunit of chromatin composed of a short length of DNA wrapped around a core of 8 histone proteins (proteins found in the chromatin of all eukaryotic cells)
  2. Coiling creates the solenoid (helical winding of nucleosome strands)
  3. Solenoid is further condensed
    - Chromatin loops are held in place by scaffold proteins
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5
Q

Explain how chromosomes are replicated before cell division.

A
  • Chromosomal DNA must be duplicated through DNA replication during the S phase of interphase, prior to mitosis.
  • Replicated chromosomes are connected to each other at their kinetochores (protein structures associated with the centromere of each sister chromatid that attract and bind spindle microtubules during prometaphase)
  • Cohesin: complex of proteins holding replicated chromosomes together
  • Sister chromatids: two copies of the chromosome within the replicated chromosome
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6
Q

Chromatid

A

One half of a duplicated chromosome
- Before replication, one chromosome is composed of one DNA molecule. In replication, the DNA molecule is copied, and the two molecules are known as chromatids

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7
Q

What is the difference between chromatin and chromatids?

A

Chromatin refers to a substance found in the cell nucleus that’s composed primarily of DNA and proteins. When cells divide, chromatin condenses to form chromosomes which split into two identical strands called chromatids. Each chromatid then becomes a chromosome in each new cell that is formed.
Chromatin - uncondensed, “loose” DNA
Chromatid - condensed DNA

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8
Q

Centromere

A

Region at which sister chromatids are bound together; a constricted area in condensed chromosomes

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9
Q

Kinetochore

A

Protein structure associated with the centromere of each sister chromatid that attracts and binds spindle microtubules during prometaphase

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10
Q

Cohesin

A

Complex of proteins holding replicated chromosomes together

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11
Q

What is the cell cycle?

A

An ordered series of events involving cell growth and cell division that produces two new daughter cells

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12
Q

Name the five main phases of the eukaryotic cell cycle.

A
  1. G1 (gap phase 1) - cell growth, early interphase
  2. S (synthesis) - chromosomes are copied, mid interphase
  3. G2 (gap phase 2) - prepares division, late interphase
  4. M (mitosis) - cell duplicates to form identical daughter cells
  5. C (cytokinesis) - “breaking” of cytoplasm
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13
Q

Interphase

A

Period of the cell cycle leading up to mitosis; includes G1, S, and G2 phases (the interim period between two consecutive cell divisions)

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14
Q

G1

A

Cell growth
- Cell accumulates building blocks of chromosomal DNA and associated proteins; accumulates energy reserves to complete DNA replication

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15
Q

S

A

DNA synthesis
- Results in identical pairs of DNA molecules (sister chromatids) that are attached at the centromeric region
- Centrosome is duplicated
- The two centrosomes will give rise to the mitotic spindle
- Centrioles aid in cell division in animal cells

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16
Q

G2

A

Prepares division
- The cell replenishes its energy stores and synthesizes proteins necessary for chromosome manipulation and movement

17
Q

Before a cell undergoes mitosis it must _____

A

Replicate its DNA

18
Q

Mitosis

A

Period of the cell cycle during which the duplicated chromosomes are separated into identical nuclei; includes prophase, prometaphase, metaphase, anaphase, and telophase

19
Q

Prophase

A
  • “Pro” = “before”
  • Chromosomes are condensed
  • Nuclear envelope breaks down
  • Mitotic spindle begins to form (made of microtubules)
20
Q

Prometaphase

A
  • Microtubules attach to kinetochores
  • Chromosomes start to move to center of the cell
21
Q

Metaphase

A
  • “M” is for “middle”
  • Chromosomes line up on metaphase/equatorial plate
22
Q

Anaphase

A
  • “A” is for “away”
  • Cohesin breaks down
  • Sister chromatids split and are pulled towards opposite poles (sister chromatids → daughter chromosomes)
23
Q

Telophase

A
  • “Telo” = “end”
  • Chromosomes are clustered at either end of cell, begin to decondense
  • Cell elongates
  • Nuclear envelope reforms
24
Q

Cytokinesis

A

Division of the cytoplasm following mitosis that forms two daughter cells
- In animals, microfilaments form a cleavage furrow
- In plants, vesicles form a cell plate

25
Q

The cell spends most of its time in _____

A

Interphase

26
Q

What is the longest phase of mitosis? Why?

A

Prophase
- Chromosomes must be condensed
- Nuclear envelope must dissolve
- Mitotic spindle must form

27
Q

What is the shortest phase of mitosis?

A

Anaphase
- Cohesin proteins degrade and sister chromatids separate as they are rapidly pulled toward opposite poles by the centrosomes

28
Q

How is the cell cycle controlled?

A

Through three main cell-cycle checkpoints:
1. G1/S
2. G2/M
3. Spindle checkpoint

29
Q

G1/S Checkpoint

A
  • Integrity of DNA is checked before replication
  • Damage, starvation, and lack of growth factors can halt replication
30
Q

G2/M Checkpoint

A
  • Ensures all chromosomes have been replicated and DNA is not damaged
31
Q

Spindle Checkpoint

A
  • Checks to see if chromosomes are properly aligned at metaphase plate and will separate correctly
32
Q

Cyclins

A

Proteins that help regulate cell cycle; act in conjunction with cyclin-dependent kinases (CDKs)
- Cyclins are the main regulatory molecules that determine the progression of the cell cycle

33
Q

PDGF

A

Platelet-derived growth factor
- Aids in wound healing

34
Q

Growth factors

A

Substances capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation

35
Q

What causes cancer?

A

Unregulated cell division
- A failure of cell cycle control that overrides checkpoints

36
Q

What genes disturb the cell cycle when mutated?

A
  • Tumor-suppressor genes
  • Proto-oncogenes
37
Q

Tumor-suppressor genes

A

Segments of DNA that code for regulator proteins that prevent the cell from undergoing uncontrolled division
- p53 is the most frequently mutated gene in human cancer (involved in G1 checkpoint - “off”/”brakes”)

38
Q

Proto-oncogenes

A

Genes that code for positive cell-cycle regulators
- Growth factors (“on”/”gas”)
- When mutated proto-oncogenes become oncogenes (genes that cause a cell to become cancerous)

39
Q

How is cell division regulated at anaphase?

A
  • Cyclin-dependent kinases (CDKs)
  • Anaphase-promoting complex/cyclosome (APC/C) marks securin (protein involved in metaphase-anaphase transition and anaphase onset) for destruction with ubiquitin
  • Securin destroys separase
  • Separase cuts cohesin

BIO 101 (15 decks)

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