Week 4_Cell division_eukaryotic cell cycle

Question 1

what is a chromosome?

Answer 1

condensed molecules of DNA associated with proteins

a chromosome contains a particular set of genes

Question 2

describe chromosome nomenclature:

Answer 2

you can have a 1-chromatid chromosome

you can have a 2-chromatid chromosome

Question 3

what is a centromere?

Answer 3

an area of repetitive DNA sequence in a chromosome

Question 4

what holds the 2 chromatids together in a 2-chromatid chromosome?

Answer 4

cohesion proteins

Question 5

during cell division, ___ attach to the centromere of each sister chromatid

Answer 5

2 types of proteins
- cohesion proteins
- kinetochore proteins

Question 6

what are cohesion proteins?

Answer 6

holds the sister chromatids together after DNA replication (inner part of the centrosomes)

Question 7

what are kinetochore proteins?

Answer 7

outer part of the centromeres

the site of microtubule attachment during cell division

Question 8

what are telomeres?

Answer 8

repetitive sequences of DNA that protect and stabilize the ends of chromosomes

Question 9

each time a cell divides, the telomeres become ___

Answer 9

shorter

Question 10

each time a cell ___, the telomeres become shorter

Answer 10

divides

Question 11

once the telomeres become too short, the cell…

Answer 11

can no longer divide

Question 12

telomere length can be maintained by the enzyme ___

Answer 12

telomerase

Question 13

most cells in the body stop producing telomerase after ___

Answer 13

embryonic development

Question 14

in ~90% of human cancers, telomerase production has been ___

Answer 14

reactivated

Question 15

each human cell contains ~___ of DNA

Answer 15

2 meters

Question 16

the nucleus of a human cell, which contains the DNA, is only ~___ in diameter

Answer 16

6 micrometers

Question 17

how does DNA coil?

Answer 17

DNA has a (-) charge
histone proteins have a (+) charge

146 bp of DNA wraps around 8 histone proteins to form a nucleosome

nucleosomes coil into a selenoid

selenoids are compacted further into supercoils

the level of DNA compaction changes (it’s dynamic)

Question 18

what is chromatin?

Answer 18

chromosomal DNA associated with proteins

Question 19

what is a nucleosome?

Answer 19

the basic unit of chromatin

Question 20

how is a nucleosome made?

Answer 20

146 bp of DNA wrapped around 8 histone protiens

Question 21

describe the DNA compaction levels

Answer 21

DNA wraps around histone proteins to form nucleosomes

nucleosomes coil into selenoids

selenoids compact further into supercoils

Question 22

during lower level of DNA compaction, individual chromosomes ___ distinguishable

Answer 22

are not

Question 23

during higher level of DNA compaction, individual chromosomes ___ distinguishable

Answer 23

are

Question 24

cell division in eukaryotes is under strict genetic control in a process called the ___

Answer 24

cell cycle

Question 25

list the 5 main phases of the cell cycle:

Answer 25

G1 S G2 M cytokinesis

Question 26

describe G1:

Answer 26

1st phase of cell cycle first gap phase (pre-DNA replication carry out metabolic activity and preparing for DNA replication

Question 27

describe S:

Answer 27

2nd phase of cell cycle DNA synthesis == DNA replication

Question 28

describe G2:

Answer 28

3rd phase of cell cycle 2nd gap phase (post-DNA replication) metabolize and prepare for DNA segregation

Question 29

describe M:

Answer 29

4th phase of cell cycle mitosis (or meiosis) DNA is segregated

Question 30

describe cytokinesis

Answer 30

5th phase of cell cycle division of cytoplasm into 2 cells

Question 31

what is Interphase? what phases make up interphase?

Answer 31

G1, S, G2 the metabolically active period b/n nuclear divisions

Question 32

mitosis + cytokinesis is...

Answer 32

sometimes collectively called "mitosis" but they are separate events

Question 33

the cell cycle is an oscillation b/n ___, ___, and ___

Answer 33

interphase, mitosis, and cytokinesis

Question 34

what is G0?

Answer 34

the cell is in a non-dividing state

Question 35

the cell cycle is controlled in part by a class of proteins called ___

Answer 35

cyclins

Question 36

what are cyclins?

Answer 36

regulatory proteins that accumulate and degrade in a cell-cycle specific fashion

Question 37

without cyclin proteins, the cell cycle would ___

Answer 37

stop

Question 38

cyclins regulate....

Answer 38

kinases and CDKs

Question 39

what are kinases?

Answer 39

protein enzymes that phosphorylate (add a phosphate group to) other molecules

Question 40

what are phosphatases?

Answer 40

enzymes that dephosphorylate (remove a phosphate group from) other molecules

Question 41

how does an enzyme get activated?

Answer 41

getting phosphorylated

Question 42

cyclins regulate ___ (CDKs)

Answer 42

cyclin dependent kinases

Question 43

what are CDKs and how are they activated?

Answer 43

kinases that are inactive unless they are attached to a cyclin protein

Question 44

when activated by a cyclin, CDKs can...

Answer 44

phosphorylate and activate target proteins that are necessary to advance the cell cycle

Question 45

the activation of CDKs by cyclins ultimately results in...

Answer 45

the activation of specific genes that are necessary to advance the cell cycle

Question 46

describes steps and progression of the cell cycle

Answer 46

1) cyclins are produced 2) inactive CDKs 3) active cyclin/CDK complex 4) CDK phosphorylates/activates target proteins 5) activated target proteins advance the cell cycle

Question 47

cyclins are needed to proceed through ___

Answer 47

cell cycle checkpoints

Question 48

what are cell cycle checkpoints?

Answer 48

points during the cell cycle at which the progression of the cell cycle can be stopped

Question 49

what is the purpose of having cell cycle checkpoints?

Answer 49

defense against: - improper environmental conditions - incompletely replicated or damaged DNA - misaligned chromosomes

Question 50

what are the 3 main cell cycle check points?

Answer 50

1) G1/S transition (start or restriction checkpoint) 2) G2/M transition checkpoint 3) Spindle checkpoint

Question 51

describe the G1/S transition checkpoint

Answer 51

start or restriction checkpoint the commitment to divide at all regulated by cyclin/CDKs

Question 52

describe the G2/M transition checkpoint

Answer 52

the commitment to proceed into mitosis regulated by cyclin/CDKs

Question 53

describe the Spindle checkpoint

Answer 53

commitment to segregate the replicated DNA to opposite ends of the cell (anaphase) regulated by APC (anaphase promoting complex) APC is not a cyclin/CDK complex

Question 54

what happens if the cell fails the test at any checkpoint?

Answer 54

cell division is halted for repairs or cell death is induced (apoptosis)

Question 55

what do the cyclin/CDKs check for in G1/S checkpoint?

Answer 55

proper environmental conditions sufficient nutritional state of cell sufficient size of cell

Question 56

what do cyclin/CDKs check for in G2/M checkpoint?

Answer 56

is DNA completely replicated no DNA damage sufficient size of cell

Question 57

what do APCs check for in "spindle" checkpoint?

Answer 57

are the chromosomes aligned properly for DNA segregation

Question 58

genes that control ___ are the most frequently mutated genes in all forms of cancer

Answer 58

the cell cycle

Question 59

describe how cancer cells continue to accumulate mutations and become more and more difficult to treat

Answer 59

cells start the cell cycle when they shouldn't cells proceed to mitosis/cytokinesis when they shouldn't cells don't die when they should (evasion of apoptosis)