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Histology Exam 1 TonyFrim > Nucleus > Flashcards

Nucleus Flashcards

1
Q

Components of nucleus

A

nuclear envelope(membrane), nucleoplasm, chromatin, nucleolus

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2
Q

Chromatin of nucleus contains

A

DNA encoding genetic apparatus of chromosomes

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3
Q

nuclear pores are formed by the fusion of

A

the inner and outer nuclear membranes and associated with nuclear pore complex

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4
Q

Nuclear pore complex contains how many different proteins

A

> 450 different proteins

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5
Q

What is a nuclear pore complex?

A

proteins arranged around each nuclear pore in an octagonal symmetry (cylindrical aqueous channel opening)

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6
Q

What can diffuse across NPC?

A

Ions, small molecules and proteins

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7
Q

Transport of larger molecules in across NPC requires

A

nuclear pore receptor proteins (fibril associated)

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8
Q

All proteins in the nucleus are imported from

A

cytoplasm

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9
Q

Nuclear pore receptor proteins recognize what on the protein?

A

nuclear localization signals

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10
Q

When larger molecules are recognized they are transported via

A

active transport

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11
Q

Protoplasm surrounded by nuclear envelope

A

nucleoplasm

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12
Q

two forms of chromatin that reside with the nucleus

A

heterochromatin and euchromatin

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13
Q

Where is heterochromatin located in the nucleus

A

concentrated at nucleus periphery, around the nucleolus and scattered throughout the nucleoplasm

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14
Q

Heterochromatin is transcriptionally

A

inactive

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15
Q

Euchromatin is transcriptionally

A

active

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16
Q

Chromatin

A

Double stranded DNA in chromatin complexed with histones and non-histone acidic proteins.

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17
Q

Histones have

A

+charged amino acids that bind to DNA

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18
Q

Nucleosome

A

fundamental packing unit of chromatin

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19
Q

How many copies of each histone does nucleosome contain?

A

2 copies of each H2A, H2B, H3, and H4, which form the nucleosome core around which the DNA double helix is wrapped two full turns

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20
Q

Describe what composes the “beads of a string” analogy for chromatin

A

beads= nucleosomes; string=linker DNA

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21
Q

condensed chromatin contains

A

an additional histone, H1, which wraps around groups of nucleosomes forming 30nm diameter fibers, the structural unit of the chromosome

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22
Q

When do chromosomes become visible?

A

Chromosomes become visible during mitosis and meiosis when their chromatin is condensed

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23
Q

Barr body

A

corresponds to one of the two X chromosomes; present in nearly all somatic cells of female mammals

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24
Q

What phase is the barr body (inactive X chromosome) visible as a dark staining evagination protruding from the nucleus

A

Interphase

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25
Q

Two major periods of cell cycle

A

Interphase and Mitosis

26
Q

Cells in G0 state

A

Temporarily suspended in nondividing resting cells. Such cells may reenter cycle and divide again

27
Q

Which is longer? Interphase or Mitosis

A

Interphase is much longer

28
Q

Period during which cell doubles in size and DNA content

A

Interphase

29
Q

Three phases of interphase

A

G1, S, and G2

30
Q

Cells that fail to reach restriction point become

A

resting cells and enter the G0 state

31
Q

How long does the G1 phase last

A

lasts from a few hours to several days

32
Q

In the cell cycle, G1 phase(gap phase) occurs when

A

Just after mitosis-cell growth and protein synthesis occur-restoring daughter cells to normal volume and size

33
Q

The synthesis of regulatory proteins in G1 phase enables the cell to

A

reach a threshold(restriction point) and proceed to S phase

34
Q

What occurs in the S phase (synthetic phase)

A

DNA replication and protein synthesis occur. Chromosomes duplicated

35
Q

Centrioles in S phase

A

self-duplicated

36
Q

Cells in S phase will uptake

A

tritiated thymidine- counted in scintillation counter or by autoradiography

37
Q

When does G2 phase(gap phase) occur in the cell cycle?

A

Follows the S phase and extends to mitosis

38
Q

What occurs in G2 phase (the gap phase)

A

Cell resting and preparing to divide: centrioles grow to maturity; energy for mitosis is stored; RNA and proteins necessary for mitosis are synthesized

39
Q

Cell cycle control factors

A

cyclins; cyclin-dependent kinases

40
Q

CDK

A

cyclin dependent kinases

41
Q

Cyclins and cyclin dependent kinases basic function

A

regulate the cell cycle and move it in one direction

42
Q

How are cyclins and cyclin dependent kinases controlled

A

controlled by regulatory proteins – inhibit activity of kinases (cyclin kinase inhibitors) and degrade cyclins (polyubiquinated and degraded by proteosome

43
Q

Start Kinase is used to

A

initiate S phase

44
Q

M-phase promoting factor

A

initiate mitosis

45
Q

Two primary ways to control cell cycle

A

1) Regulation of genes that suppress cell proliferation 2) Regulation of growth factors that stimulate cell growth

46
Q

Tumor suppressor gene-Normal cell has

A

2 copies of retinoblastoma gene.(Normal Rb protein prevents mitosis (entry into S phase))

47
Q

If one copy of Rb mutated

A

other copy of gene still suppresses growth

48
Q

Mutation in both tumor suppressor genes

A

results in abnormal Rb gene product and cancer

49
Q

p53

A

DNA repair gene which exhibits frequent mutations; p53 acts prior to DNA replication by detecting DNA damage and delaying entry into S phase until damage repaired

50
Q

mutation in how many of four subunits may result in an abnormal p53 protein

A

mutation in 1 of 4 p53 subunits may result in abnormal p53 protein

51
Q

When does mitosis occur

A

follows the G2 phase and completes the cell cycle

52
Q

Karyokinesis

A

Division of the nucleus

53
Q

Division of the cytoplasm

A

cytokinesis

54
Q

Mitosis results in

A

two identical daughter cells

55
Q

Centrosome

A

Pericentriolar material plus associated 2 centrioles oriented orthogonally to each other. Centrosomes function as microtubule organizing centers and function as the mitotic spindle pole during mitosis

56
Q

Astral microtubules

A

radiate from centrosomes; function to separate the spindle poles and position them in the cell

57
Q

Polar microtubules

A

extend from each pole and overlap in middle of cell- responsible for pushing poles of cells apart

58
Q

Kinetochore microtubules

A

attach to kinetochore that forms at the centromere of duplicated chromosomes- moves separated daughter chromatids to each pole

59
Q

Centromere

A

constriction in the middle of the attached sister chromatids where a protein complex (kinetochore) is assembled. Kinetochore microtubules
will attach to the kinetochore and pull the sister chromatids towards opposite poles of the cell

60
Q

Normal process of programmed cell death. May be triggered by multiple pathways and stimuli (cytokines, toxins, hormones, and other cell stressors – radiation, viruses, oxygen or nutrient deprivation)

A

Apoptosis

61
Q

When are caspases activated

A

Caspases are activated in apoptosis and drive apoptotic cascade

62
Q

Function of caspases

A

cleave cell proteins and activate other enzymes like DNAse

Histology Exam 1 TonyFrim (8 decks)

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