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SL12003 Genetics > Cellular reproduction > Flashcards

Cellular reproduction Flashcards

1
Q

effect of mitosis on allele frequency

A

none

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2
Q

meiosis allele frequency

A

fair
half gametes are A, other half a (of a heterozygote)

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3
Q

binary fission

A

the circular bacterial DNA molecule is attached by proteins to the inner membrane. DNA replication begins at origin of replication and proceeds bidirectionally around the circle. newly synthesised DNA molecule is also attached to the inner membrane. cell elongates symmetrically during replication, separating the DNA attachment sites
synthesis of cell membrane and wall at midpoint
daughter cells separate

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4
Q

bacterial genome organisation

A

highly organised-replication
highly expressed genes cluster near origin of replication
genes mainly on leading strand to prevent DNA polymerase and RNA polymerase clashing
genes with similar functions cluster and are co-expressed (operons)

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4
Q

karotype

A

portrait formed by the number of shapes of chromosomes representative of a species

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4
Q

chromosome structure

A

sister chromatids connected by centromere (gene poor domains)
telomeres are stable ends of chromosomes
kinetochore (spindle attachment)

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5
Q

G1 phase

A

size and protein content of cell increased
many regulatory proteins made and activated

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5
Q

G0 phase

A

only in cells that are not actively dividing

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6
Q

s phase

A

duplication of chromosomes
each chromosome has 2 sister chromatids

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7
Q

prophase

A

chromosomes condense
centrosomes duplicated, begin to migrate to opposite poles and radiate microtubules

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8
Q

prometaphase

A

microtubules attach to chromosomes at kinetochores, growing and shrinking to explore nucleus
nuclear membrane breaks down

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9
Q

kinetochores

A

2 protein complexes associated with centromeres (one on each side of the centromere)
each complex associated with a sister chromatid
site of microtubule attachment

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10
Q

metaphase

A

chromosomes align in a single plane that is roughly equidistant from both of the spindle poles (metaphase plate)

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11
Q

anaphase

A

sister chromatids separate
centromere divides

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12
Q

telophase

A

nuclear envelope reforms and chromosomes decondense
nuclear envelope reforms around each set of chromosomes

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13
Q

cytokinesis

A

division into 2 daughter cells
ring of actin filaments (contractile ring) forms against inner face of cell membrane at cell equator
ring contracts, pinching cytoplasm

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14
Q

cytokinesis in plants

A

phragmoplast formed during telophase in the middle of the cell. consists of overlapping microtubules that guide vesicles containing cell wall components to the middle of the cell
vesicles fuse to create a new cell wall during late anaphase/telophase called the cell plate
fuses with original cell wall

15
Q

number of chromosomes vs number of DNA molecules

A

chromosomes-number of centromeres
DNA molecules- involves sister chromatids

16
Q

meiosis 1

A

separation of homologous chromosome pairs

17
Q

meiosis 2

A

separation of sister chromatids
similarity to mitosis suggests meiosis evolved from mitosis

18
Q

prophase 1

A

synapsis: homologous chromosomes line up to form bivalents
Crossing over
chromosomes condensed
nuclear envelope broken down
meiotic spindle

19
Q

crossing over

A

recombination
random
helps hold bivalents together
chiasma form

20
Q

prometaphase 1

A

nuclear envelope broken down
meiotic spindles attach to kinetochores

21
Q

metaphase 1

A

bivalents move to centre randomly (in terms of which side maternal and paternal go)

22
Q

anaphase 1

A

2 homologous chromosomes of each bivalent separate
no splitting of centromeres
23 pairs at each pole
reductional division

23
Q

telophase 1

A

cytoplasm divides
chromosomes dont completely decondense
nuclear envelope can briefly reappear

24
Q

prophase II

A

chromosomes fully recondensed
nuclear envelope disappears
spindle forms

25
Q

Prometaphase II

A

spindle attaches to kinetochores

26
Q

metaphase II

A

chromosomes line up

27
Q

anaphase II

A

centromere splits
chromatids to opposite poles

28
Q

telophase II

A

chromosomes uncoil
nuclear envelope reforms
cytokinesis
equational division (cells in meiosis II have the same number of chromosomes at the beginning and end)

29
Q

sources of variation

A

crossing over
independent segregation
gamete fusion/fertilisation

30
Q

independent assortment

A

metaphase 1
different ways the homologous chromosomes align

31
Q

effect of meiosis on allele frequencies

A

none, fair
it can affect frequencies of different combinations of alleles at different loci

32
Q

cyclins

A

regulate cell cycle
activate enzymes called cyclin-dependent kinases which promote cell division

33
Q

G1/S cyclic-CDK complex

A

active at end of G1
promotes expression of histone proteins needed for packaging the newly replicated DNA
prepares cell for S phase

34
Q

S cyclin-CDK complex

A

initiates DNA synthesis
activates protein complexes involved in DNA replication that contain enzymes necessary for DNA synthesis.

35
Q

M cyclin-CDK complex

A

initiates multiple events associated with mitosis
breakdown of nuclear envelope during prophase
formation of mitotic spindle

36
Q

checkpoints

A
  1. DNA replication checkpoint (check for presence of unreplicated DNA at end of G2)
  2. DNA damage checkpoint (before S phase)
  3. spindle assembly checkpoint (all chromosomes attached to spindle)
37
Q

DNA damage checkpoint

A

When DNA is damaged by radiation, a specific protein kinase is activated that phosphorylates the p53 protein.
Under normal conditions, p53 is exported from the nucleus at very low levels.
When phosphorylated, p53 is prevented from being exported and its levels in the nucleus rise.
As p53 levels rise, p53 activates the transcription of a gene that expresses a CDK inhibitor protein.
This inhibitor binds to and blocks the activity of the G1/S cyclin–CDK complex.
This arrests the cell at the G1/S transition, giving the cell time to repair the DNA damage.

SL12003 Genetics (18 decks)

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