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BIO 111 > Chapter 10 > Flashcards

Chapter 10 Flashcards

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Biology 101 flashcards
1
Q

Bacterial Cell Division

A

bacteria divide by binary fission
* no sexual life cycle
* reproduction is clonal

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2
Q

Replication of Bacteria

A
  • replication begins at the orgin of replication and proceeds bidirectionally to site of termination
  • new chromosomes are partitoned to opposite ends of the cell
  • septum forms to divide the cell into 2 cells
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3
Q

Eukaryotic Chromosomes

A
  • every species has a different # of chromosomes
  • humans have 46 chromosomes (23 pairs) sex cells don’t have 46
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4
Q

Chromosomes

A
  • composed of chromatin: complex of DNA (40%) and protein (60%)
  • DNA of a single chromosome is one long continuous double-stranded fiber
  • in the nondividing nucleus:
    Heterochromatin: not expressed
    Euchromatin: expressed
  • human chromosome 140 millon nucleotides long
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5
Q

Chromosome Structure

A
  • nucleosome: complex of DNA and histone proteins (promotes and guides coiling of DNA) “basic packing”
  • DNA duplex coiled around 8 histone proteins every 200 nucleotides
  • histones are positively charged, strongly attracted to negative charged phosphate groups in DNA
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6
Q

Solenoids

A

solenoids are nucleosomes wrapped into higher order coils
- leads to a fiber 30 nm in diameter
- usual state nondividing (interphase) chromatin
* during mitosis, chromatin in solenoid arranged around scaffold of protein to achieve maximum compaction
- radical looping aided by condensin proteins

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7
Q

Karyotype

A

a particular array of chromosomes in an individual organism
- arranged according to size, staining properties, location of centromere

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8
Q

define Haploid and Diploid

A

Haploid (n): 1 set of chromosomes (23 in humans)
Diploid (2n): humans (2 compete sets, 46 total)
* pair of chromosomes are homologous

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9
Q

Replication

A
  • prior to replication, each chromosome composed of a single DNA molecule
  • after replication, each chromosome composed of 2 identical DNA molecules (held together by cohesin proteins)
  • visible as 2 stands held together as chromosome become more condensed
  • 1 chromosome composed of 2 sister chromatids
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10
Q

Eukaryotic Cell Cycle

A
  1. G1 (gap phase 1): primary growth phase, longest phase
  2. S (synthesis): replications of DNA
  3. G2 (gap phase 2:) organelles replicate, microtubules organize
  4. M (mitosis): subdivided into 5 phases (seperate DNA)
  5. C (cytokinesis): separation of 2 new cells (seperate cell)
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11
Q

Cell Cycle Duration

A
  • time it takes to complete varies
  • mature cells take longer to grow
  • growth occurs during G1, G2, and S phase
  • most variation in length of G1
    (resting phase is G0: brain cells stay here forever)
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12
Q

Interphase

A

G1: cells undergo major portion of growth
S: replicates DNA
G2: chromosomes coil more tightly using motor proteins
* Centromere: point of constriction
* kinetochore: attachment site for microtubules
* each sister chromatid has a centromere
* Chromatids stay attched at centromere by cohesin

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13
Q

5 Phases of Mitosis

A

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

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14
Q

Prophse

1st phase in mitosis

A
  • stops making RNA
  • chromosomes start to condense (spindle apparatus begins)
  • nuclear envelope breaks down
  • asters: radial array of microtubulse in animals (not plants)
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15
Q

Prometaphase

2nd step in Mitosis

A
  • microtubule attachment (attaches to kinetochores)
  • sister chromatids (connected to opposite poles)
    chromosomes (move to center of cell-congression)
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16
Q

Metaphase

3rd step in Mitosis

Meta = Midde

A
  • alignment of chromosomes along metaphase plate
  • (not an actual structure)
  • future axis of cell division
17
Q

Anaphase

4th step in Mitosis

A
  • begins when centromeres split
  • removal of cohesin proteins from all chromosomes
  • sister chromatids pulled to opposite poles
  • Anaphase A: kinetochores pulled toward poles
  • Anaphase B: poles move apart
18
Q

Telophase

5th step in Mitosis

A
  • spindle apparatus disassembles
  • nuclear envelope forms around each set of sister chromatids (now called chromosomes)
  • chromosomes begin to uncoil (RNA genes to be expressed)
  • nucleolus reappears in each new nucleus
19
Q

Cytokinesis

A
  • cuts cells into 2 identical cells
  • animal cells: constriction of actin filaments produce a cleavage furrow
  • plant cells: cell plate forms between the nuclei
  • fungi: nuclear membrane doesn’t dissolve; division of the nucleus occurs with cytokinesis
20
Q

Control of the Cell Cycle

A

2 concepts:
1. Cell cycle has 2 irreversible points
- replicaiton of DNA (synthesis)
- separation of the sister chromatids
2. Cell cycle can be put on hold at specific points called checkpoints
- process is checked for accuracy and can be halted if there are errors
- allows the cell to respond to internal and external signs

21
Q

3 Cell Cycle Checkpoints

A
  1. G1/S checkpoint
    - cell “decides” to divide
    - primary point of external signal influence
  2. G2/M checkpoint
    - cell makes a commitment to mitosis
    - assesses success of DNA replication
  3. Late metaphase (spindle) checkpoint
    - cell ensures that all chromosomes are attached to the spindle
22
Q

Cyclin-dependent kinases (Cdks)

A
  • enzymes that phosphorylate proteins
  • primary mechanism of cell cycle control
  • Cdks partner with other cyclins at different points in the cell cycle
  • Cdk itself is controlled by phosphorylation
23
Q

Cdk-cyclin complex

A
  • also called mitosis-promoting factor (MPF)
  • Activity of Cdk is also controlled by the pattern of phosphorylation
    • phosphorylation at one site inactivates Cdk
    • phosphorylation at another site activates Cdk
24
Q

Anaphase-promoting Complex

A
  • aka cyclosome (APC/C)
  • function of the APC/C is to trigger anaphase itself
  • makes securin for destruction; no inhibition of separase; separase destroys cohesin
25
Q

Control in Multicellular Eukaryotes

A
  • multiple Cdks control the cycle as opposed to 1 Cdk in yeast (eukaryote)
  • animal cells respond to more external signals
  • yeast only respond to signals necessary for mating
26
Q

Growth Factors

A
  • act by triggering intracellular signaling systems
  • platelet-derived growth factor (PDGF) one of the 1st growth factor identified
  • growth factors can override cellular controls that otherwise inhibit cell division
27
Q

Cancer

A
  • unrestrained, uncontrolled growth of cells
  • failure of cell cycle control
    2 kinds of genes can distrub the cycle when they are mutated:
    1. Tumor-suppressor genes
    2. Proto-oncogenes
28
Q

Tumor-Suppressor Genes

A
  • P53 plays a key role in G1 checkpoint
  • P53 protein monitors integrity of DNA
    • if DNA is damaged, cell divison halted and repair enzymes are stimulated
    • if DNA damage is irreparable, p53 directs cell to kill itself (apoptosis)
  • Prevents the development of mutated cells containing mutations
  • P53 is absent/damaged in many cancerous cells
  • Both copies of a tumor-suppressor gene must lose function for the cancerous phenotype to develop
29
Q

Proto-oncogenes

A
  • normal cellular genes that become oncogenes when mutated (oncogenes can cause cancer)
  • some encode receptors for growth factors
    • if receptor is mutated in “on”, cell no longer depends on growth factors
  • some encode signal transduction proteins
  • Only 1 copy of the proto-oncogene needs to undergo this mutation for uncontrolled division to take place
30
Q

Metastasis

A

cells travel to start new tumors

Cancer Cells

31
Q

Angiogenesis

A

form new blood vessels to nourish themselves

Cancer Cells

32
Q

Benign

A

contained with a capsule

33
Q

Malignant

A

invasive and may spread

34
Q

Cancer Cells

A
  • don’t undergo apoptosis
  • form tumors: do not respond to inhibitory signals
35
Q

Cancer Treatment

A
  • remove the tumor
  • interfere with the ability of the cancer cells to reproduce
  • Radiation and Chemo because cancer cells are rapidly dividing
  • Hormone therapy designed to prevent cells from receiving signals for continued growth and division
36
Q

BRCA

A
  • BRCA mutation increases the risk of breast cancer
  • tumor suppressor gene

BIO 111 (12 decks)

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