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Biology 121 > Sheet 8--Test 3 > Flashcards

Sheet 8--Test 3 Flashcards

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1
Q

What is the cell cycle?

A

Eukaryotes–> interphase (not dividing) and cell division

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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

Make sure there is two times as much cytoplasm and organelles
—more imporant= daughter cells get correct copy of genome

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3
Q

how do prokaryotic cells divide?

A

Binary fission–asexual

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4
Q

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

A

2 replication complexes meet on opposite sides of origin of replication

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5
Q

where do bacteria add new cell wall and plasma membrane as they grow

A

between mesosomes (mesomes attach chromosomes to cell membrane)

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6
Q

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

A

..

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7
Q

how do eukaryotic cells divide?

A

Mitosis: division of genomes
–genome–> DNA of an organism
why Mitosis? growth, repair, replace

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8
Q

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

A

Genome is larger–> organelles must be replaced

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9
Q

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

A

Organizes and compresses DNA

–spool (histone) of thread (DNA)

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10
Q

what is chromatin? and what is the differnce between heterochromatin and euchromatin?

A

State of chromosome when they are thin and spread out in nucleus during interphase
–chromatin is a mixture of protein, DNA and some RNA

Heterochromatin– highly condensed chromatin
Euchromatin– less condensed chromatin, can access genes–this is only condensed in mitosis to help move it

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11
Q

What are histones?

A
  • -Proteins around which DNA wraps
    • +charge, DNA has - charge–> neutalized overall charge
  • -compress and organize DNA
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12
Q

What are Nucleosomes, what is the function?

A
  • -Fundamental packaging unit of DNA
  • -each has 2 of H2A, H2B, H3, H4
  • -compress DNA
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13
Q

How can our cells compress 2 meters of DNA into a nucleus less that 10 nanometers in diameter?

A

DNA–> Nucleosome –> solenoids –> extended section chromosome –> condensed loop –> metaphase chromosome

Nucleosome–every 200nucleotides, DNA is coiled around 8 histone proteins

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14
Q

What are the 5 levels of compression

A

1) nucleosome
2) solenoid
3) extended section chromosome
4) condensed loop

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15
Q

what are chromosomes?

A

structure in which genetic material is stored and transmitted to next generation
–DNA + Histones = Chromosomes

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16
Q

What are chromatid?

A

identical copy of same DNA molecule

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17
Q

What are homologous chromosomes?

A

similar copies of same DNA moleucle–get one from mom and one from dad
–have same length, position of centromere, same genes but the genes have different traits

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18
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 molecule

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19
Q

what is a centromere?

A

site where sister chromatids are attached

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20
Q

What is a kinetochore?

A

protein attached to centromere to which microtubules attach

–spindle fiber = microtubule = protein fiber

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21
Q

what is a karotype and why is it useful?

A

array of individuals chromosomes

  • -can be used to detect genetic defects
  • – Aneuplody- differen # of chromosomes and cancer
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22
Q

what is ploidy?

A

number of homologous chromosomes
2m–diploid– 2 copies of each chromosome
–somatic cells, which are all cells except for gametes

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23
Q

what are the two stages and five divisions of the eukaryotic cell?

A

1) Interphase– G1, S (replicateDNA), and G2

2) Cell division– Mitosis and cytokinesis

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24
Q

what are the three division of interphase and what happens during each?

A 
Interphase (longest phase)
G1
----Primary growth phase
---- phase
----Follows cytokinesis
----Make more of cell
----Determine if condition favor cell division
S 
----DNA synthesis
G2
----Quality control
----No DNA damage? Conditions ok to divide
----Chromosomes begin to condense
----Cells start building mitotic apparatus
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25
Q

What are the 4 phases of mitosis? and what happens?

A

..

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26
Q

How are the chromosomes aligned on the metaphase plate?

A

microtubules pull chromosomes back and forth between asters

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27
Q

what holds the sister chromatids together during metaphase?

A

centromeres

28
Q

how are the chromosomes separated during anaphase?

A

microtubules shorten and pull sister chromatids apart

29
Q

what is the difference between mitosis and cytokinesis?

A

mitoisis is the division of nuclues and the distribution of chromosomes

cytokinesis is the division of the cytoplasm

30
Q

how do we know they are seperate proceses?

A

can poison one without affecting the other

31
Q

How do animals perform cytokinesis and how do plants perform cytokinesis?

A

..

32
Q

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

A

..

33
Q

Why dont plants need asters?

A

because they have cell walls that are regid

34
Q

How do eukaryotes regulate cell divsion?

A

– cell progresses through a series of checkpoints called G1, G2 and metaphase

35
Q

What checkpoint is most important and why is it the most important?

A
  • -G1 is most important
  • -asses if conditions are right because you dont want to copy DNA until ready.
  • -S phase follows G1–> S is the synthesis of DNA so it makes sense that G1 chekcs the DNA
36
Q

What is MPF and what does it do?

A

Mitosis promoting factor

  • -chemical that promotes mitosis–> it causes prophase (1st stage of mitosis)
  • -Need to make MPF in stage before prophase, which is G2.

Has 2 subunits:

1) catalytic subunit CDK
2) Regulatory unit is cuclin

37
Q

What are cyclins and what do

A
  • -regulate cell cycle
  • –determine what CDKs (enzyme) will act in and how active it will be
  • –different cyclins are made at different times, have to be attached to CDK for CDK to work
38
Q

How does SPF sense if a cell is ready to enter S. and how does it then initiate the transition to S?

A

Synthesis promoting factor–made during G1

  • -activated by a variety of sensors- Food?, DNA? cell large enough?
  • -if good, SPF turns on genes responsible for proteins that do DNA syntheis
  • -3 hour lag then DNA is synthesized
  • -SPF and MPF have same CDK, different Cyclin
39
Q

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

A

MPF is activated by sensors for growth factors and amount of food–it is INHIBITED by DNA damage

  • -the transition to mitosis involves the phosphorlyations of proteins, especially nuclear lamins, which cause the nuclear membrane to break down
    • condenses chromosomes
  • -assemble mitotic appartus
40
Q

How is the metaphase checkpoint regulated?

A

Check:

    • are all chromosomes on metaphase plate?
  • -does each kinetochore have spindle fiber?

**this is checked by pulling chromosomes back and forth

41
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
42
Q

Why must MPF be destruyed for cells to exit mitosis?

A

MPF keeps cells in mitosis

–when prophase is done, MPF must leave or it will stay in that stage

43
Q

How do multicellular organisms regulate cell division?

A
  • rely on the presence of growth factor at cell surface receptor
  • -sets off phosphorylation cascade that activates SPF. results is passing start
44
Q

Why do you get cancer when proto-oncogenes go wild?

A
  • -proto oncogenes are genes that normally activate cell division
    • if they become oncogenes, they no longer control cell division and cancer occurs
45
Q

Why do you get cancers when tumor surporessors go bad?

A

tumor supressors normally inhiit cell division

ex. Rb

46
Q

What is P53 and what does it do?

A

P53 senses DNA damage; halts cell until DNA is fixed active during G2

  • -70% of cancers have defective p53
    • DNA is replicated in S, G2, occurs after S so it is checking DNA that was replicated correctly
47
Q

What is Rb and what does it do?

A
  • -retinoblastoma protein–tumor supressor gene
  • -master break of cell cycle
  • -dephosphorylsted in G1
  • -releases then whem kinased by SPF
  • –SPF kinasaes Rb–> releases proteins needed for S
  • defective Rb allows these proteins to act too soon
  • *40% of cancers have defective Rb
48
Q

How do you recognize a plant cells in cytokinesis?

A

2 nuclei at opposite ends of cells

–formation of cell plate

49
Q

which phase of the cell cycle lasted longest in onion root tips?

A

interphase

50
Q

how can muscles get larger in adult humans?

A

increase size by increaseing the size fo cells, not by increasing cell number
–muscle cells do not do mitosis

51
Q

When does APC become inactive?

A

when all kinetochore are bound to microtubules

52
Q

what trigger anaphase?

A

APC

53
Q

when is MPF made? and does it trigger

A

G2 and it trigger mitosis

54
Q

what are the 2 subunits of MPF?

A

CDK and cyclin

55
Q

what is checked during metaphase?

A

1) all chromosomes are on metaphase plate

2) each kinetochore has spindle fibers connected

56
Q

how is chromosomes checked during metaphase?

A

by pushing and pulling chromosomes

57
Q

what is known as the master break of the cell cycle?

A

RB

58
Q

when is RB dephosphorylated?

A

G1

59
Q

what kinases Rb and what occurs when it is?

A

SPF kinases and it releases proteins needed to start S

60
Q

Bacterial cells divide as the?*

A

plasma membrane pinches inward constricting the cell

61
Q

What is ploidy?*

A

The number of copies of each homologous chromosome in a cell

62
Q

Which of the following is essentially the reverse of prophase?*

A

telophase

63
Q

The array of microtubules that appears in cell division and eventually moves the chromatids apart is the?*

A

spindle

64
Q

How do eukaryotic cells ensure that each daughter cell gets one copy of each homologous chromosome at cell division?*

A

they ensure that each chromosome has a microtubule from one pole attached to one kinetochore and a microtubule fro the other pole attached to the other before dividing.

65
Q

the proteins that control passage through the checkpoings for cell cycle control are ?*

A

cyclins and cyclin-dependent kinases

66
Q

what is checked at the G1 checkpoint?*

A

whether the cell should divide

67
Q

Why do you get cancers when proto oncogenes become hyperactive?

A

they promote cell division and thus over ride the ordinary control over cell division

Biology 121 (9 decks)

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