Cellular reproduction

Question 1

effect of mitosis on allele frequency

Answer 1

none

Question 2

meiosis allele frequency

Answer 2

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

Question 3

binary fission

Answer 3

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

Question 4

bacterial genome organisation

Answer 4

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)

Question 4

karotype

Answer 4

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

Question 4

chromosome structure

Answer 4

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

Question 5

G1 phase

Answer 5

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

Question 5

G0 phase

Answer 5

only in cells that are not actively dividing

Question 6

s phase

Answer 6

duplication of chromosomes
each chromosome has 2 sister chromatids

Question 7

prophase

Answer 7

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

Question 8

prometaphase

Answer 8

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

Question 9

kinetochores

Answer 9

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

Question 10

metaphase

Answer 10

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

Question 11

anaphase

Answer 11

sister chromatids separate
centromere divides

Question 12

telophase

Answer 12

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

Question 13

cytokinesis

Answer 13

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

Question 14

cytokinesis in plants

Answer 14

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

Question 15

number of chromosomes vs number of DNA molecules

Answer 15

chromosomes-number of centromeres
DNA molecules- involves sister chromatids

Question 16

meiosis 1

Answer 16

separation of homologous chromosome pairs

Question 17

meiosis 2

Answer 17

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

Question 18

prophase 1

Answer 18

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

Question 19

crossing over

Answer 19

recombination
random
helps hold bivalents together
chiasma form

Question 20

prometaphase 1

Answer 20

nuclear envelope broken down
meiotic spindles attach to kinetochores

Question 21

metaphase 1

Answer 21

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

Question 22

anaphase 1

Answer 22

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

Question 23

telophase 1

Answer 23

cytoplasm divides chromosomes dont completely decondense nuclear envelope can briefly reappear

Question 24

prophase II

Answer 24

chromosomes fully recondensed nuclear envelope disappears spindle forms

Question 25

Prometaphase II

Answer 25

spindle attaches to kinetochores

Question 26

metaphase II

Answer 26

chromosomes line up

Question 27

anaphase II

Answer 27

centromere splits chromatids to opposite poles

Question 28

telophase II

Answer 28

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

Question 29

sources of variation

Answer 29

crossing over independent segregation gamete fusion/fertilisation

Question 30

independent assortment

Answer 30

metaphase 1 different ways the homologous chromosomes align

Question 31

effect of meiosis on allele frequencies

Answer 31

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

Question 32

cyclins

Answer 32

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

Question 33

G1/S cyclic-CDK complex

Answer 33

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

Question 34

S cyclin-CDK complex

Answer 34

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

Question 35

M cyclin-CDK complex

Answer 35

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

Question 36

checkpoints

Answer 36

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)

Question 37

DNA damage checkpoint

Answer 37

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.