BIOL1025 - Spindle Assembly Checkpoint and mitosis

Question 1

SAC

Answer 1

spindle assembly checkpoints

Question 2

APC/C

Answer 2

inactive until kinetochores are properly attached to the MT

Question 3

SAC function

Answer 3

keeps APC/C inactive during prometaphase

Question 4

After proper attachment of MT to kinetochores are made

Answer 4

APC/C activated and performs 2 major functions

Question 5

2 major function of when APC/C is activated

Answer 5

Ubiquitinates Securin

ubiquitinates cyclin B

Question 6

Ubiquitinates Securin

Answer 6

after securin destruction - releases/activates separase

which removes cohesin (cleavage) from centromere - triggers anaphase

Question 7

Ubiquitinates cyclin B

Answer 7

after cyclin B destruction - inactivatesCdk1 therefore leads to mitotic exit

Question 8

cohesion of sister chromatids

Answer 8

established after DNA synthesis
cohesin and DNA catenation responsible for this
during S phase

Question 9

mitosis stages

Answer 9

prophase, prometaphase, metaphase, anaphase, telophase and cytokinesis

Question 10

prophase

Answer 10

replicated chromosomes - sister chromatids condense

mitotic spindle assembles between 2 centrosomes that have been replicated and moved apart

Question 11

prometaphase

Answer 11

breakdown of nuclear envelope (NEBD)

chromosome attach to spindle MT via kinetochores and undergo active movement

Question 12

prometaphase of cell

Answer 12

nuclei dissolves - open mitosis

Question 13

closed mitosis

Answer 13

nuclei in cells remain intact - not complete breakdown of nucleus

Question 14

metaphase - chromosomes

Answer 14

aligned at equator of spindle - midway between spindle poles

Question 15

metaphase - kinetochores MT

Answer 15

attaches to sister chromatids to opposite poles of spindle

Question 16

anaphase - sister chromatids

Answer 16

synchronously separate to 2 daughter chromosomes and pulled slowly to spindle poles it faces

Question 17

anaphase - kinetochores MT

Answer 17

gets shorter and spindle poles move apart

both processes contribute to chromosome segregation

Question 18

telophase - chromosomes

Answer 18

2 daughter chromosomes arrive at poles of spindles and decondense

Question 19

telophase - nuclear envelope

Answer 19

new nuclear envelope reassembles around each set = complete formation of 2 nuclei and end of mitosis

Question 20

telophase - spindles and cytoplasm

Answer 20

central spindles are formed

division of cytoplasm begins with contraction contractile rings

Question 21

cytokinesis

Answer 21

cytoplasm divide by contractile ring of actin and myosin filaments
by pinching cells in 2 daughter each with one nucleus

Question 22

mitotic spindle assembly

Answer 22

MT have inherent polarity

Question 23

mitotic spindle assembly - dynamic nature of MT

Answer 23

slowly depolymerisation at negative end and rapid polymerisation/depolymerisation at positive end

Question 24

drug inhibitor

Answer 24

such as colchicine

Question 25

function of colchicine

Answer 25

binds to alpha-beta-tubulin interface and blocks polymerisation of MT- shortening and depolymerisation of MT at metaphase

Question 26

kinetochores

Answer 26

large multiprotein complexes responsible for attachment to MT of mitotic spindle - assembled on centromeric chromatin

Question 27

lack of proper connection between kinetochore and MT fibre cause

Answer 27

activation of SAC and induces cascade of events - inhibiting APC/C

Question 28

function of inhibited APC/C

Answer 28

stop progression of mitosis in metaphase - gives cells more time to repair/generate proper attachments between MT and kinetochores

Question 29

inhibiting APC/C allows…

Answer 29

protection against improper segregation(mis-segregation) of chromosomes

Question 30

cells treated with MT destabilisers such as colchicine

Answer 30

cells accumulate all phase up to and including metaphase and won’t progress until drug is removed

Question 31

how kinetochores are assembled

Answer 31

early during mitosis on centromeres

Question 32

how centromeres are assembled

Answer 32

part of chromosomes where primary construction - fragment of DNA which allows chromatid segregation during mitosis

Question 33

where kinetochores are assembled

Answer 33

region on chromosomes

Question 34

human kinetochores function

Answer 34

multiplies MT to form connection between mitotic spindle and chromosomes

Question 35

inner kinetochores

Answer 35

sits close to centromeric chromatid

Question 36

outer kinetochores

Answer 36

binding to MT to mitotic spindle

Question 37

positive end of MT

Answer 37

project away from spindle pole

Question 38

negative end of MT

Answer 38

anchored at spindle poles

Question 39

kinetochores MT

Answer 39

connect spindle poles with kinetochores of sister chromatid

Question 40

interpolar MT

Answer 40

form 2 poles interdigitate at spindle equator

Question 41

astral MT

Answer 41

radiates out from poles into cytoplasm and frequently contact cell cortex

Question 42

segregated chromosomes

Answer 42

packaged in daughter nuclei at telophase and entire cell divides - cytokinesis

Question 43

mitotic cyclin

Answer 43

destroyed and other proteins that well phosphorylated at entry to mitosis is dephosphorylated

Question 44

end of mitosis

Answer 44

chromosomes decondense and cells centre interphase