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Biology 121 > Questions # 8 > Flashcards

Questions # 8 Flashcards

October 17-22

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1
Q

What is the cell cycle?

A

The repeating sequence of growth and division through which cells pass each each generation.

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2
Q

What are the two main problems cells need to solve in order to divide, and which is more important?

A
  1. Make sure there is two times as much cytoplasm, organelles, ect.
  2. Make sure daughter cells get exact copy of genome.
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3
Q

How do prokaryotic cells divide?

A

Binary fission

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4
Q

How do prokaryotes know when they have finished replicating their genomes?

A

Two replication complexes meet on opposite sides of origin of replication (terminus of replication)

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5
Q

Where do bacteria add new cell wall and plasma membranes as they grow?

A

Between mesosomes

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6
Q

How do prokaryotes ensure that each cell gets a copy of the genome after cell division?

A

Plasma memvran pinches between mesosomes; cell wall forms between mesosomes.

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7
Q

How do eukaryotic cells divide?

A

Mitosis (growth, repair, replace)

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8
Q

Why is cell division more complicated in eukaryotic cells than prokaryotic cells?

A

Genome is larger and organelles must be replicated.

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9
Q

why is there some much protein associated with DNA in eukaryotes?

A

Organizes and compresses DNA (histones)

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10
Q

What is chromatin, and and what is the difference between heterochromatin and euchromatin?

A

Chromatin: state of chromosomes when they are thin and spread out in the nucleus during interphase.
Euchromatin: open book
Heterochromatin: closed book

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11
Q

What are histones?

A

Positively charged proteins which DNA wraps around and neutralizes causing it to condense and organize.

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12
Q

What are nucleosomes, and what is their function?

A

fundamental packing unit of DNA which compresses DNA. This octamer histone core is made up of two H2A, H2B, H3, H4

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13
Q

How can our cells compress 2 meters of DNA into a nucleus less than um long

A

Dna–>(histone)–>nucleosome–>solenoids–>extended section chromosome–>cordinoid loop–>metaphase chromosome

(six nucleosomes= solenoid)

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14
Q

What are the conventional five levels of compression, and why is it controversial?

A
  1. nucleosome
  2. solenoid
  3. extended section chromosome
  4. condensed loop
  5. metaphase chromosome
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15
Q

What are chromosomes?

A

Structure in which genetic material is stored and transmitted to next generation composed of histones and DNA.

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16
Q

What are homologous chromosomes?

A

similar copies of some DNA molecule; get one from mom and one from dad

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17
Q

What are sister chromatids, and how do they differ from homologous chromosomes?

A

Sister chromatids are identical copies of the same DNA molecule

Homologous chromosomes are similar copies of the same DNA

18
Q

What are centromere

A

site where sister chromatids are attached…until anaphase.

19
Q

What is a kinetochore?

A

Protein attached to centromere to which microtubules attach.

20
Q

What is a karyotype and why is it useful?

A
  • array of individual’s chromosomes

- can be used to detect genetic defects, aneuploidy, and cancer

21
Q

What is ploidy?

A

Number of homologous chromosomes

2n diploid two copies of each chromosome

1n haploid one copy of each chromosome (ie. gametes)

22
Q

What are the two stages and five divisions of the eukaryotic cell cycle?

A

Interphase/Cell division

G1 Mitosis
S Cytokinesis
G2

23
Q

What are the three divisions of interphase and what happens in each?

A 
G1
-primary growth phase
-longest phase
-follows cytokinesis
-make more cell organelles
-determine if conditions favor cell division (spf checkpoint)
S
-DNA synthesis 
G2
-quality control 
-no DNA damage? conditions ok to divide? (mf check point) 
-chromosomes begin to condense
-cells start building mitotic apparatus
24
Q

What are the four phases of mitosis and what happens during each?

A 
Prophase
-chromosomes condense
-mitotic apparatus forms 
-centrioles migrate to poles
-nuclear membrane dissolves
-microtubules attach to kinetochore 
Metaphase
-chromosomes in center
-cell checks that spindle is connected to kinetochores *M checkpoint
Anaphase
-chromatids pulled to opposite sides of cell 
Telophase
-nuclei reforms
-chromosomes decondense
-mitotic apparatus disassembled 
Cytokinesis
-division of cytoplasm  (ring of actin at cleave furrow;vesicles form making cell plate)
25
Q

How are chromosomes lined up on the metaphase plate?

A

Microtubules pull chromosomes back and forth between asters

26
Q

What holds the sister chromatids together during metaphase.

A

Centromere

27
Q

How are the chromosomes separated during anaphase?

A

Microtubules shorten and pull sister chromatids apart.

28
Q

What is the difference between mitosis and cytokinesis and how do we know they are separate processes.

A

Mitosis
division of nucleus and distribution of chromosomes

Cytokinesis
division of cytoplasm

29
Q

How do animals perform cytokinesis and hoe do plant cells perform cytokinesis?

A

Animal cells - cleavage furrow (actin ring)

Plant cells - (vesicles line up) phragoplast

30
Q

What are the main differences between cell division in plants and animals?

A
  1. During cytokinesis
    animal: cleave furrow
    plant: cell plate
  2. animal: microtubules pull against asters/centrioles
    plant: anastral microtubules pull against cell wall.
31
Q

Why don’t plants need asters?

A

Use cell wall to push against.

32
Q

How do eukaryotes regulate cell division?

A
  • cell progresses through a series of checkpoints
  • check, read to continue?
  • G1, G2, metaphase
33
Q

Which checkpoint is most important and why is it most important?

A

G1 is most important

  • asses if conditions are right
  • want to copy DNA until ready (S phase follows G1)
34
Q

What is MPF (mitosis promoting factor) and what does it do?

A

-controls G2; made during G2
-enzyme with two subunits
-catalytic subunit CDK (cyclin-dependent kinase) regulatory unit is cyclin.
(Kinase means add phosphate)

  • promotes mitosis
  • phosphorylates proteins, especially nuclear lamin, which causes nuclear membrane to break down; condenses chromosomes assembles mitotic apparatus (spindle)
  • activated by sensors for growth factor amount of food; inhibited by DNA damage.
35
Q

What are cyclins and what do they do?

A

Regulates the cell cycle.

  • determine what CDKs (enzyme) will act on and how active it will be
  • different cyclins are made at different times; have to be attached to CDK for CDK to work.
36
Q

What are cyclin dependent kinases and what do they do?

A
  • regulated by cyclin
  • enzyme that phosphorylates its substrate … a kinase
  • only active with a bound cyclin which determines what the enzyme will do
  • important in regulating the cell cycle.
37
Q

How does SPF sense i f the cell is ready to enter S and how does it then initiate the transition to S?

A 
Synthesis Promoting Factor
CDK + a different cyclin
made in G1
-activated by a varietyof sensors
     food, DNA, ready, cell large enough? 
3 hr time lag
38
Q

How does MPF sense if the cell is ready to divide, and how does it then initiate the transition to M?

A

MPF is activated by sensors for growth factors and amount of food. It is inhibited by DNA damage.

39
Q

How is the metaphase check point regulated?

A
  • are all chromosomes on metaphase plate?
  • does each kinetochore have a spindle fiber?
  • checked by pulling chromosome back and forth
40
Q

What is APC and what does it do?

A

-anaphase promoting complex
-APC is inactive until all kinetochores are bound to microtubules
-triggers anaphase; sister chromatids separate as microtubules shorten.
(APC destroys securin destroys cohesin which holds chromatids to separate.)

41
Q

Why must MPF be destroyed for cells to exit mitosis.

A

MPF keeps cell in mitosis.

42
Q

How do multicellular organisms regulate cell division ?

A
  • rely on presence of growth factor at cell surface receptor

- sets off phosphorylation cascade that activates SPF; result is passing start

Biology 121 (9 decks)

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