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mcdb1A > cell cycle and mitosis > Flashcards

cell cycle and mitosis Flashcards

1
Q

why do cells divide?

A

growth, repair, reproduce

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2
Q

prokaryotic cell division

A

cell division occurs through binary fission
dont require any signal
as long as there are nutrients in the environment they will divide
divide very rapidly, every 30 minutes
DNA in prokaryotes is usually a single chromosome that takes the form of a closed circle, so it must be extremely tightly folded

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3
Q

how do prokaryotes divide?

A

origin of replication (ori) is where replication starts
as replication starts there will be two copies of the origin of replication
these two origins will move away from each other and become tethered to the plasma membrane of the cell
origins will be pulled apart from one another in opposite directions
movement of origins of replication moving apart results in the one bacterial cell pinching in the middle to form two cells
fission results in two daughter cells

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4
Q

how is eukaryotic and prokaryotic division different

A

eukaryotes are larger and more complex with large numbers of chromosomes, many organelles, an endomembrane system, and a cytoskeleton that must be properly replicated and distributed equally to the daughter cells
cell division is rarely continuous and is regulated
need a signal to divide

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5
Q

why is it important to regulate cell division in multicellular organisms?

A

if you divide uncontrollably you can generate extra tissue or tumors

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6
Q

genome

A

collection of all dna blueprints of organism

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7
Q

how do we package 2m worth of DNA into a cell

A

package dna into chromosomes

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8
Q

chromosomes

A

linear DNA molecules with many proteins
contain hundreds to thousands of genes
humans have 46 chromosomes/ 23 pairs of them
somatic cells are diploid

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9
Q

somatic cells

A

all cells but sexual cells (gametes—> eggs/sperms)

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10
Q

having diploid chromosomes means what

A

we have two copies of each gene
one from male and one from female

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11
Q

centromere

A

waist that connects the chromatids of a paired chromatids
repetitive sequences of DNA bound by centromeric proteins

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12
Q

loci

A

specific location of a gene on a chromosome

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13
Q

alleles

A

versions of genes
same loci on a chromosome
difference in alleles changes the type of protein produced by the blueprint

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14
Q

what is constituted as a chromosome

A

I I is two chromosomes X is one chromosome

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15
Q

diploid

A

when you have two of the same version of chromosome

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16
Q

haploid

A

when u only have one subset of a pair of homologous chromosomes

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17
Q

cohesin

A

proteins that attach along the entire length of chromosomes to keep paired chromatids together

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18
Q

because we have very large genomes, packing them has to be a very precise, controlled process
thus we use

A

histones

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19
Q

histones charge

A

mostly positively charged in the point of contact with dna
important because dna is negatively charged due to its negatively charged phosphates

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20
Q

what connects histone clusters

A

linker dna

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21
Q

histone clusters are called

A

nucleosomes

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22
Q

what does the distance between nucleosomes change

A

how accessible the dna is gonna be for transcription (more or less)

23
Q

chromatin

A

dna-histone complex
come as either heterochromatin(tightly packed nucleosome complex) or euchromatin (relaxed fit of nucleeosomes)

24
Q

example of heterochromatin

A

chromosomes
tightly packed

25
Q

karyotype

A

the number and size and shape of chromosomes

26
Q

chromosome duplication

A

process called mitosis
chromosome replicates, creating two copies of each of its genes —> results in paired chromatids connected by cohesin proteins
mitosis separates the two paired chromatids from one another into two chromosomes in different daughter cells
results in two daughter cells that are genetically identical copies of the original cell
no genetic variation between daughter cells and parent cell

27
Q

eukaryotic cell cycle
4 phases

A

G1 phase
S phase
G2 phase
m phase

28
Q

interphase

A

every phase other than m phase

29
Q

m phase general descriotion

A

mitosis
division of DNA inside the cell (division of nucelus)
cytokinesis also occurs (division of daughter cells)

30
Q

G1 phase

A

gap 1
period between M phase and S phase
phase where cell carries out its function until something signals it to divide

31
Q

S phase

A

dna synthesis phase
replication occurs – > replicated chromosomes
replicated DNA

32
Q

G2 phase

A

replicate everything other than DNA
- ER, organelles, cytoskeleton, etc

33
Q

how is the cell cycle regulated

A

checkpoints
G1, G2 M checkpoints

34
Q

G1 checkpoint

A

after signal is received to replicate, the cell ensures it is in the right shape to do so
ensure that all the genes are in the right place and shape —> so that they are functional

35
Q

G2 checkpoint

A

ensure copies are correct and everything has been replicated

36
Q

M checkpoint

A

ensure dna is going to be properly divided

37
Q

experiment where cells in one phase of cell cycle are fused with a cell in a different phase

A

fusing cells allows the cells to move to a different phase of cell cycle (dependent on what phase the other cell was in)
Sharing cytoplasm allowed for this change in phase, due to CDKs presence

38
Q

kinases

A

a protein that adds a phosphate group to a protein (phosphorylate)

39
Q

Cyclin dependent kinases

A

a kinase that requires cyclin to work
CDK will phosphorylate many proteins and activate or inhibit their activity
Covalently add phosphate to proteins and regulate how they work
CDK is always there but its active site is not always exposed
Cyclin is made when the cell must move to the next phase/ when it is required
Cyclin binding to cdk changes its conformation, exposing its active site
A protein substrate and ATP bind to cdk and protein is phosphorylated

40
Q

How cdk governs the cell cycle

A

Many pairs of cyclin and cdk
Work as checkpoint of cell cycle

41
Q

example of cdk

A

Maturation promoting factor (MPF)
Exists between G2 and M phase at a checkpoint
Allows for cell to go into mitosis
Cyclin concentration goes down after M phase, so MPF activity also goes down

42
Q

Checkpoint triggers

A

G1
Dna damage
S
Incomplete replication or DNA damage
G2
Dna damage
M
Chromosome unattached to spindle

43
Q

Mitosis
Goal:

A

Separate duplicated DNA in the chromosome to the 2 daughter cells
The daughter cells are genetically identical

44
Q

5 phases of mitosis

A

Prophase
Prometaphase
Metaphase
Anaphase
Telophase

45
Q

mitosis interphase

A

Pre-mitosis stages
Nuclear envelope encloses nucleus
Nucleus still maintains nucleolus
Two centrosomes(make spindle fibers) have formed by duplication
Chromosomes are duplicated during S-phase but have yet to condense

46
Q

mitosis prophase

A

Chromatin fibers become tightly coiled and condense into discrete chromosomes
Nucleoli disappear ( nucleolus)
Each duplicated chromosome appears as two identical paired chromatids joined at the centromere
Mitotic spindle begins to form
Centromeres move away from one another (waist of chromosomes)
Want to center in the cell

47
Q

mitosis prometaphase

A

Nuclear envelope fragments
Microtubules extend from each centrosome, invading ex-nuclear space
Kinetochores. A specialized protein structure, forms at the centromere of each chromatid

48
Q

metaphase

A

Centrosomes(type of mtoc) are now at opposite poles of the cell
Chromosomes have arrived at metaphase plate (center of ell)
Plane that is equidistant between spindles two poles
The kinetochores of paired chromatids attach to kinetochore microtubules coming from each pole

49
Q

Mitotic spindle

A

assembly of microtubules and their associated proteins that move chromatids around

Kinetochore microtubules attach to chromatids at their centromeres

50
Q

Polar microtubules

A

Microtubules that don’t attach to kinetochores but serve to center the spindle

51
Q

Aster

A

Serve to center spindle in the cell

52
Q

anaphase mitosis

A

Cohesin protein degrades, allowing sister chromatids to part

Each chromatid is now an independent chromosome
Daughter chromosomes move towards opposite ends of cell as kinetochore microtubules shorten
Polar microtubules extend, pushing cell apart

53
Q

mitosis telophase

A

Two daughter nuc;lei form in the cell, nuclear envelope arise from fragments of parent cell’s nucleus
Nucleoli reappear
Chromosomes decondense
Spindle microtubules depolymerase

54
Q

Cytokinesis

A

Break two cells apart
In animals
You develop a contractual ring of microfilaments (pinch)
In plant cells
Vesicles form cell plate creating a new cell wall/cell plate

mcdb1A (11 decks)

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