Nucleus

Question 1

Components of nucleus

Answer 1

nuclear envelope(membrane), nucleoplasm, chromatin, nucleolus

Question 2

Chromatin of nucleus contains

Answer 2

DNA encoding genetic apparatus of chromosomes

Question 3

nuclear pores are formed by the fusion of

Answer 3

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

Question 4

Nuclear pore complex contains how many different proteins

Answer 4

> 450 different proteins

Question 5

What is a nuclear pore complex?

Answer 5

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

Question 6

What can diffuse across NPC?

Answer 6

Ions, small molecules and proteins

Question 7

Transport of larger molecules in across NPC requires

Answer 7

nuclear pore receptor proteins (fibril associated)

Question 8

All proteins in the nucleus are imported from

Answer 8

cytoplasm

Question 9

Nuclear pore receptor proteins recognize what on the protein?

Answer 9

nuclear localization signals

Question 10

When larger molecules are recognized they are transported via

Answer 10

active transport

Question 11

Protoplasm surrounded by nuclear envelope

Answer 11

nucleoplasm

Question 12

two forms of chromatin that reside with the nucleus

Answer 12

heterochromatin and euchromatin

Question 13

Where is heterochromatin located in the nucleus

Answer 13

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

Question 14

Heterochromatin is transcriptionally

Answer 14

inactive

Question 15

Euchromatin is transcriptionally

Answer 15

active

Question 16

Chromatin

Answer 16

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

Question 17

Histones have

Answer 17

+charged amino acids that bind to DNA

Question 18

Nucleosome

Answer 18

fundamental packing unit of chromatin

Question 19

How many copies of each histone does nucleosome contain?

Answer 19

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

Question 20

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

Answer 20

beads= nucleosomes; string=linker DNA

Question 21

condensed chromatin contains

Answer 21

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

Question 22

When do chromosomes become visible?

Answer 22

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

Question 23

Barr body

Answer 23

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

Question 24

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

Answer 24

Interphase

Question 25

Two major periods of cell cycle

Answer 25

Interphase and Mitosis

Question 26

Cells in G0 state

Answer 26

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

Question 27

Which is longer? Interphase or Mitosis

Answer 27

Interphase is much longer

Question 28

Period during which cell doubles in size and DNA content

Answer 28

Interphase

Question 29

Three phases of interphase

Answer 29

G1, S, and G2

Question 30

Cells that fail to reach restriction point become

Answer 30

resting cells and enter the G0 state

Question 31

How long does the G1 phase last

Answer 31

lasts from a few hours to several days

Question 32

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

Answer 32

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

Question 33

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

Answer 33

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

Question 34

What occurs in the S phase (synthetic phase)

Answer 34

DNA replication and protein synthesis occur. Chromosomes duplicated

Question 35

Centrioles in S phase

Answer 35

self-duplicated

Question 36

Cells in S phase will uptake

Answer 36

tritiated thymidine- counted in scintillation counter or by autoradiography

Question 37

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

Answer 37

Follows the S phase and extends to mitosis

Question 38

What occurs in G2 phase (the gap phase)

Answer 38

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

Question 39

Cell cycle control factors

Answer 39

cyclins; cyclin-dependent kinases

Question 40

CDK

Answer 40

cyclin dependent kinases

Question 41

Cyclins and cyclin dependent kinases basic function

Answer 41

regulate the cell cycle and move it in one direction

Question 42

How are cyclins and cyclin dependent kinases controlled

Answer 42

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

Question 43

Start Kinase is used to

Answer 43

initiate S phase

Question 44

M-phase promoting factor

Answer 44

initiate mitosis

Question 45

Two primary ways to control cell cycle

Answer 45

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

Question 46

Tumor suppressor gene-Normal cell has

Answer 46

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

Question 47

If one copy of Rb mutated

Answer 47

other copy of gene still suppresses growth

Question 48

Mutation in both tumor suppressor genes

Answer 48

results in abnormal Rb gene product and cancer

Question 49

p53

Answer 49

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

Question 50

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

Answer 50

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

Question 51

When does mitosis occur

Answer 51

follows the G2 phase and completes the cell cycle

Question 52

Karyokinesis

Answer 52

Division of the nucleus

Question 53

Division of the cytoplasm

Answer 53

cytokinesis

Question 54

Mitosis results in

Answer 54

two identical daughter cells

Question 55

Centrosome

Answer 55

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

Question 56

Astral microtubules

Answer 56

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

Question 57

Polar microtubules

Answer 57

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

Question 58

Kinetochore microtubules

Answer 58

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

Question 59

Centromere

Answer 59

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

Question 60

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)

Answer 60

Apoptosis

Question 61

When are caspases activated

Answer 61

Caspases are activated in apoptosis and drive apoptotic cascade

Question 62

Function of caspases

Answer 62

cleave cell proteins and activate other enzymes like DNAse