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BIOL243 > 2D: inheritance of DNA > Flashcards

2D: inheritance of DNA Flashcards

1
Q

define binary fission

A

the entire mechanism of prokaryotic cell division

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2
Q

what are the 3 parts of binary fission?

A

B period
C period
D period

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3
Q

what is the binary fission B period?

A

the period of growth before and after reproduction. not always present if enough nutrients in environment

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4
Q

define nucleoid

A

the central region in prokaryotes where their single circular chromosome is compacted

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5
Q

what is the binary fission C period?

A

the period where the chromosome is duplicated and the two resulting chromosomes separate to opposite parts of the cell

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6
Q

define ori

A

the origin of replication is the specific region of DNA on a bacterial chromosome where DNA replication starts. is located in the middle of the cell before replication occurs

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7
Q

how does period C of binary fission progress?

A

DNA replication takes place in the centre of the cell and starts at the ori. as the DNA is replicated, the two ori’s move to opposite ends of the cell. the two resulting daughter chromosomes move to opposite ends of the cell. the cell elongates during this process

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8
Q

what is the binary fission D period?

A

the period where the membrane pinches together and two daughter cells are formed

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9
Q

how does period D of binary fission progress?

A

once chromosomes are replicated and separated, the plasma membrane grows inward and a new cell wall is synthesized. D period ends once the two daughter cells are separated

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10
Q

why is binary fission efficient for prokaryotes but wouldn’t be for eukaryotes?

A

because prokaryotes only have one chromosome and so do not need to worry about organizing them like eukaryotes do

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11
Q

what is the structure of a chromosome composed of two chromatids?

A

two chromatids, bound together all along their length by proteins called cohesins. the centromere is where the two sister chromatids are closest to each other (the centre of the X shape of the chromosome). the kinetochores (proteins to which the spindle binds during mitosis) are by the centromere on each sister chromatid

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12
Q

define chromosome segregation

A

the equal distribution of daughter chromosomes into each of two daughter cells that result from cell division

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13
Q

what are the 4 phases of the cell cycle?

A

➝ M phase (mitosis)
➝ G1
➝ S
➝ G2

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14
Q

what happens during the G1 phase?

A

phase in which cell carries out its function and, in some cases, grows

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15
Q

what happens in S phase?

A

DNA and centriole duplication occurs (chromosomes are not visible)

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16
Q

what happens in G2 phase?

A

brief gap in cycle where cell growth continues and the cell prepares for mitosis

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17
Q

what is G0 phase?

A

(pronounced G not) resting phase. the usual state human cells are in

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18
Q

on what phase does the speed of cell division rely?

A

it depends on G1 because this is the only phase with a variable length

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19
Q

define cyclin

A

control proteins that monitor the cell’s progression through the cell cycle

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20
Q

where in the cell cycle are the 3 checkpoints?

A

① G1/S
② G2/M
③ mitotic spindle: prometaphase/metaphase

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21
Q

what does the G1/S checkpoint do?

A

checks if DNA is okay for replication. determines if the cell will enter the cell cycle at all

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22
Q

what does the G2/M checkpoint do?

A

checks that DNA is fully replicated before mitosis.

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23
Q

what does the mitotic spindle checkpoint do?

A

checks that all chromosomes have attached to the spindle and can align at the centre plate properly before moving on

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24
Q

define CDKs

A

cyclin-dependent kinases. protein kinase that phosphorylates and thereby regulates the activity of particular target proteins that play roles in initiation or regulation of key events of the cell cycle

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25
when are CDKs active?
only when bound to cyclin, stops being active when the bound cyclin degrades
26
are cyclins always present?
no, they're only expressed in specific phases of the cell cycle, which determines when CDKs are active
27
define tumour
tissue masses that have deviated from their normal genetic program and divide and grow inappropriately
28
define dedifferentiation
the process by which cells revert to their embryonic developmental state
29
what is the difference between a benign and malignant tumour?
the tumour is benign if the growth does not affect other cells and stays together in a single mass. it is malignant if it disrupts surrounding tissues
30
define cancer
a malignant tumour. growth caused by uncontrolled division
31
define metastasis
the spreading of a malignant tumour
32
define familial cancer
hereditary cancer
33
define sporadic cancer
nonhereditary cancer
34
define driver mutation
a mutation confers a selective growth advantage to the cell (drives tumour formation)
35
define driver gene
gene that contains a driver mutation or is expressed abnormally, resulting in cells having a selective advantage
36
define passenger mutation
additional mutations a cancer cell has that do not contribute to selective growth advantage for the cell
37
define oncogene
a gene that, when activated by a mutation or altered to increase expression, confers a selective growth advantage on the cell
38
define proto-oncogene
the nonmutated version of an oncogene in a normal cell
39
define tumour suppressor gene
gene that, when inactivated mutation or otherwise downregulated, results in a selective growth advantage to the cell
40
is cyclin D/E an oncogene or tumour suppressor gene?
oncogene
41
are cdk4 alleles an oncogene or tumour suppressor gene?
oncogene
42
is checkpoint gene p53 an oncogene or tumour suppressor gene?
tumour suppressor
43
is checkpoint gene RB an oncogene or tumour suppressor gene?
tumour suppressor
44
which gene is inactivated in 50% of tumours?
the p53 gene
45
why is it hard to find a universal cure for cancer?
each cancer is caused by different gene mutations
46
define homologous chromosomes
chromosome pair where one came from the each parent (in diploid organisms), so they're the same chromosome but with different alleles
47
what are the 5 stages of mitosis?
``` ① prophase ② prometaphase ③ metaphase ④ anaphase ⑤ telophase ```
48
how is DNA compacted?
into 10 nm chromatin fibre, which is further compacted into 30 nm chromatin fibre
49
describe how DNA is compacted in 10nm chromatin fibre
double helix is wound twice around a complex of histones (H2A, H2B, H3, and H4 {2 of each}) to form a nucleosome. linker DNA connects nucleosomes together
50
describe how DNA is compacted in 30nm chromatin fibre
histone H1 binds to nucleosomes and linker DNA, packaging it into a coiled structure
51
what is an alternate name for 30nm chromatin fibre?
solenoid
52
what 3 things occur in prophase? (mitosis)
➝　DNA is condensed into chromosomes made up of two sister chromatids and becomes visible ➝　nuclear envelope breaks down and disappears ➝　duplicated centrioles (centrosomes, from S phase) move farther apart (to form spindle poles)and form mitotic spindles
53
what 2 things occur in prometaphase?
➝　spindles attach to kinetochore of chromosomes (one microtubule from each spindle) ➝　microtubules start to move all the chromosomes to the equator of the cell
54
what 1 thing occurs in metaphase?
➝　spindle reaches its final form and chromosomes fully align at the metaphase plate (the equator)
55
define karyotype
the complete collection of condensed chromosomes, arranged according to size and shape
56
what 3 things occur in anaphase?
➝　cohesins are degrading, allowing sister chromatids to separate ➝　sister chromatids are pulled towards the spindle poles (chromosome segregation is completed) ➝　centrosomes move farther apart
57
what 4 things happen in telophase?
➝　spindle disassembles ➝　chromosomes at each pole decondense ➝　nuclear envelope reforms ➝　cytokinesis begins (division by furrowing)
58
when does cytokinesis occur?
usually following the nuclear division stage of mitosis (telophase or late anaphase)
59
how does cytokinesis through furrowing occur?
a layer of microtubules at the former spindle midpoint expand until they stretch across the whole cell. as this layer develops, a band of microfilaments forms just inside the plasma membrane. the microfilaments slide together, tightening the band and constricting the cell, which forms a groove that deepens as they slide together more, until the cell is split in two
60
how does cytokinesis through cell plate formation occur?
the layer of microtubules left over at the spindle midpoint act as a guide for where the cell wall will form. vesicles are produced by the endoplasmic reticulum and Golgi complex. as the vesicles fuse together, their contents assemble into a new cell wall (the cell plate). the membranes of the vesicles becomes the inner membranes of the daughter cells
61
what happens to microtubules during interphase?
the comprise a major part of the cell cytoskeleton (in eukaryotes)
62
define centrosome
a site near the nucleus from which the microtubules of the spindle originate. the centrosome is the main MTOC
63
what does MTOC stand for?
MicroTubule Organizing Centre
64
where are centrioles located?
usually arranged at right angles to each other, contained in the centrosome.
65
what is the primary function of centrioles?
to generate the microtubules needed for flagella or cilia
66
how is the mitotic spindle formed?
① during S phase, centrioles within the centrosome duplicate. ② as prophase begins, the centrosome separates into two parts. ③ these parts (each containing a centriole) continue to separate until they are on opposite ends of the nucleus (as they move apart, the microtubules between them lengthen and increase in number), resulting in the early spindle ④ when the nuclear envelope breaks down, the spindle moves into the area it used to occupy and expands until it fills the cytoplasm
67
define aster
centrosomes at the spindle tips, which form the poles of the spindle
68
what are the two types of microtubules present in spindles once the spindle is fully formed?
➝　kinetochore microtubules | ➝　nonkinetichore microtubules
69
what is the function of nonkinetochore microtubules?
they extend the spindle poles without connecting to chromosomes. they overlap with the tubules from the opposing spindle at the spindle midpoint
70
define meiocyte
cell that is destined to divide by meiosis
71
how does mitotic and meiotic S phase and G1 phase compare?
in meiosis they are the same as in mitosis
72
define synapsis
the pairing of homologous chromosomes with each other, lengthwise, gene for gene
73
what are all the stages of meiosis?
``` meiosis I: ① prophase I ② prometaphase I ③ metaphase I ④ anaphase I ⑤ telophase I interkinesis meiosis II: ① prophase II ② prometaphase II ③ metaphase II ④ anaphase II ⑤ telophase II ```
74
what are the steps of prophase I?
① chromosomes begin to condense ② two chromosomes of each homologous pair line up side by side with genes matching up (synapsis), forming tetrads ③ while paired, chromosomes in tetrads physically exchange segments (recombination) as prophase I finishes, a spindle forms in the cytoplasm
75
define tetrad
homologous chromosomes paired together side by side with the genes matching up, where each chromosome consists of two sister chromatids and the chromatid of one homologous chromosome is bound to that of the other by the synaptonemal complex
76
what happens in prometaphase I?
➝　nuclear envelope breaks down and spindle enters former nuclear area ➝　the two chromosomes of each tetrad attach to kinetochore microtubules (the sister chromatids of one homologous chromosome in the tetrad both bind to the same spindle, and those of the other chromosome bind to the other spindle)
77
what happens in metaphase I?
the spindle aligns the tetrads on the metaphase plate between the two spindle poles
78
what happens in anaphase I?
the two chromosomes of each tetrad separate and move to opposite spindle poles
79
what happens in telophase I?
brief, transitory stage where there is little or no change in the chromosomes. cytokinesis occurs
80
what happens during interkinesis?
the first meiotic spindle disassembles and a new spindle is created for the second division. DNA replication does not occur
81
what is the result of meiosis I?
two haploid daughter cells are produced from the parent cell, each containing two chromatids per chromosome. the sister chromatids are not identical due to crossing over (recombination)
82
what happens during prophase II?
chromosomes condense
83
what happens during prometaphase II?
the nuclear envelope dissolves, the spindle enters the former nuclear area, and spindle microtubules attach to the kinetochore of each chromatid (like in mitosis prophase)
84
what happens in metaphase II?
movement of chromosomes within the spindle brings them to rest at the metaphase plate
85
what happens in anaphase II?
sister chromatids of each chromosome separate and move to opposite spindle poles. once separated and at their poles, they are now called chromosomes
86
what happens in telophase II?
chromosomes decondense, the spindles disassemble, and a new nuclear envelope forms around the masses of chromatin as the cells divide (cytokinesis)
87
what is the result of meiosis II?
(in respect to original parent cell) 4 haploid cells have formed, where each chromosome consists of only one chromatid and all carry various new combinations of the organism's maternal and paternal genes

BIOL243 (14 decks)

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