chapter 6- cell division Flashcards
1
Q
how much of a cell life does it spend in interphase
A
90-95%
2
Q
how many divisions take place in mitosis
A
1 nuclear
1 cytoplasmic
3
Q
daughter cells are what to the parent cell
A
genetically identical to the parent cell
4
Q
in eukaryotes the cell cycle is divided into 2 major phases
A
interphase and the mitotic phase
5
Q
is interphase an active or passive phase and what does that mean
A
active as respiration occurs
6
Q
what are the 3 phases in interphase
A
gap/growth stage (G1)
synthesis (S)
gap/growth stage (G2)
7
Q
what happens in G1
A
getting dna ready to replicate
cytoplasm increases in volume as it will need to be shared (so growth in cell size)
production of proteins for organelles to be replicated
types of rna (biochemicals) made ready for s phase
organelles synthesised
8
Q
what happens in the S phase
A
dna replication so that its ready for mitosis
9
Q
what happens in the G2 phase
A
ATP levels increased ready for mitosis
increases in cell size due to increase in cytoplasm volume.
error checking of dna
10
Q
where is the centromere located
A
in the centre of a chromosome
11
Q
in a relicated chromosome (x) what are the 2 branches called
A
sister chromatids
12
Q
what is a pair of homologous chromosomes
A
The two chromosomes in a homologous pair are very similar to one another and have the same size and shape. Most importantly, they carry the same type of genetic information: that is, they have the same genes in the same locations. However, they don’t necessarily have the same versions of genes.
13
Q
what is never visible in interphase
A
chromosomes
14
Q
how long does the cell cycle take for a human cell
A
24hrs ish
15
Q
what are the 3 stages of the cell cycle and put them in order of size
A
interphase
mitosis
cytokinesis
16
Q
the cell cycle in not a life cycle as it happens
A
repeatedly
17
Q
chromatin is wrapped around
A
histone proteins
18
Q
what is not visible in interphase
A
chromosomes, so dna is visible as chromatin
19
Q
an x looking chromosome means that
A
the chromosomes have been replicated
20
Q
what happens at the G1 (end) checkpoint
A
check for:
nutrients (energy)
growth factors
dna damage
21
Q
if the G1 checkpoint fails then what will happens
A
it will enter G0
22
Q
how can cancer cells replicate freely
A
they reproduce quickly and over produce growth factors and so can slip through the checkpoints
23
Q
what happens at g2 checkpoint
A
check for:
cell size
dna replication (faults)
if there is a fault then the process pauses and it will be repaired, otherwise faulty dna will be passed on daughter cells
24
Q
which stage of mitosis has a checkpoint
A
metaphase
25
what happens at the metaphase checkpoint
checks that all the chromosomes are attached to spindle fibres and that they are aligned
26
chromosome/dna activity in interphase
dna replicates but is visible as chromatin not chromosomes
27
status of the nuclear envelope in interphase
present and intact, complete
28
what else happens in interphase but only in animal cells
centrioles replicate
29
Animal cells contain an organelle called the ......... which is made up of two structures called ........
This is where .......... form during metaphase.
centrosome
centrioles
spindle fibres
30
what is the chromosome activity in prophase in mitosis
early: chromatin condenses and coils to form chromosomes (into pairs of sister chromatids this will appear darker as it will take up more stain
31
status of the nuclear envelope in prophase in mitosis
it breaks down but only later on
32
what happens to the sf in prophase in mitosis
they form from the centrioles and migrate to the poles
33
chromosome activity in metaphase in mitosis
align at the equator on the metaphase plate which is held in place
34
status of the nuclear envelope in metaphase in mitosis
not present
35
sf activity in metaphase in mitosis
they attach to the centromeres of the chromosomes
36
which phase of mitosis is the longest and why
metaphase because it has a checkpoint
37
chromosome activity in anaphase in mitosis
sister chromatids separate
38
is there a nuclear envelope in anaphase in mitosis
no
39
sf activity in anaphase in mitosis
sf contract (shorten) pulling the sister chromatids apart and towards the poles
40
what shape does the sister chromatid make when it is pulled by a sf
a v shape
41
chromosome activity in telophase in mitosis
chromatids assemble at opposite poles
chromatids condense back into chromatin
42
status of nuclear envelope at telophase in mitosis
reforms around each set of chromosomes at each pole
43
what else happens in prophase in mitosis, nucleolus...
the nucleolus breaks down
44
what else happens in telophase in mitosis, the nucleolus
the nucleuolus reforms
45
sf activity in telophase in mitosis
they breakdown and detatch from sister chromatids
46
why is mitosis important
tissue repair and replacement of damaged cells
organism growth: derive new cells via mitosis
asexual reproduction
development of embryos: zygotes undergo mitosis and differentiate to become embryos > multicellular organisms
47
what does the centromere do in mitosis
keeps the 2 sister chromatids together
sf attach to the kineticore
48
what is used for looking for faults in dna
carrier type
49
do prokaryotes carry out mitosis
no
50
how long do rbcs live for
120 days
51
how many divisions does meiosis
2 nuclear
2 cytoplasmic
52
what type of cells does mitosis make
somatic
53
what type of cells does meiosis make
gametes
54
does crossing over occur in mitosis or meiosis
meiosis
55
reason for meiosis
to make gametes for sexual reproduction, without haploid gametes a diploid zygote would not be possible
56
in asexual reproduction there is no ....... as the offspring are........ of the parent. this is because they inherit the same ...... as the parents.
variation
clones
genes
57
in sexual reproduction each ...... is different. therefore when...... occurs chromosomes from the father mixed with chromosomes from the mother so the offspring have a combination of ..... giving rise to variation
gamete
fertilisation
alleles
58
gametocytes (germline cells) are what
eukaryotic germ cells that divide by meiosis into gametids during gametogenisis
59
male gametocytes are called
spermatocytes
60
female gametocytes are called
oocytes
61
what happens in prophase I in meiosis
dna condenses and chromosomes become visible
homologous chromosomes undergo synapsis whereby they pair up to form a bivalent,
are held together at points called chiasmata.(where the crossing over occurs)
centrioles migrate to the opposite poles and the spindle is formed
the nuclear envelope breaks down and the nucleolus disintegrates
62
which stage does crossing over occur in meiosis
prophase 1 ONLY
63
how many bivalents in a human cell
23 (a pair of chromsomes=1)
64
result of prophase 1
physical change of genetic material and all 4 haploid daughter cells will be genetically distinct as the sister chromatids will no longer be identical
once the chiasmata are formed the homologous chromosomes fully condense as bivalents and then are separated (later)
65
what happens in metaphase 1
the bivalents line up along the equator (mp) of the spindle (RANDOMLY) with the sf attached to the centromeres. independent assortment occurs. nuclear membrane fully breaks down
66
what is independent assortment
occurs during metaphase 1. the maternal and paternal pairs of chromsomes position themselves separate from the others and can end up facing either pole (orientation) so can result in many different combinations of alleles facing the poles, IA results in genetic variation
67
what happens in anaphase 1
the homologous pairs are pulled by sf to the opposite ends of the spindle (whole chromosomes), the centromeres do not divide
v shape created
68
what happens in telophase 1
sf start to break down
nuclear envelopes start to form around the 2 groups of chromosomes and nucleoli reform.
69
what can be different about plant cells in meiosis
some go straight to meiosis 2 without the reformation of the nucleus in telophase 1
70
process of cytokinesis in animals 3/4
cell surface membrane pinches inwards, by the cytoskeleton, creating a cleavage furrow in the middle of the cell which contracts dividing the cytoplasm in half
cleavage furrow forms around the middle of the cell and the cell surface membrane is pulled inwards by the cytoskeleton until it is close enough to fuse around the middle forming two cells
71
cytokinesis in plants
plant cells have cell walls so a cleavage furrow cannot form.
vesicles from the golgi begin to assmble in the same place the metaplate was formed.
72
what else generally happens in cytokinesis
the cell organelles also get distributed between the 2 developing cells
73
there is no ......... between meiosis 1 and meiosis 2 so the dna is ... ........
interphase
not
replicated
74
what happens in prophase 2
the nuclear envelope breaks down and chromosomes condense
a spindle forms at a right angle to the old one
there is no pair of chromosomes so crossing over cannot occur
75
what happens in metaphase 2
chromosomes line up in a single file along the equator of the spindle, IA can occur
76
define stem cell
a cell that is unspecialised and undifferentiated
77
which is true about stem cells
a) stem cells naturally divide to produce a new organism
b) stem cells in adult humans can divide into a limited range of cell types
b
78
what 2 qualities of stem cells
self renewal and potency
79
what is self renewal
they can continuously divide and replicate
80
what is potency
they have the capacity to differentiate into specialised cell types
81
what is the potency and source of totipotent stem cells
p: can form any cell type including extra embryonic tissue (total potential), can differentiate into any cell and are capable of forming whole organisms
s: zygote during the first mitotic divisions (first 1-4 days)
82
potency and source of pluripotent (embryonic) stem cells
p: can form any cell type but cannot form whole organisms, can differentiate into most cells
s: early embryos/blastocysts
83
potency and source of multipotent (adult) stem cells
p: can differentiate into a number of closely related cell types within a tissue
s, can differentiate into a limited number of cells
s: bone marrow
84
Multipotent stem cells are found in the bone marrow. What two cell types can they differentiate into?
erythrocytes and neutrophils.
85
what are haemopoietic stem cells
multipotent, found in bone marrrow and long bones not brain or muscle
86
unipotent stem cells
cannot differentiate but can self renew eg muscle stem cells
87
Which of the following are issues with using stem cells in scientific study?
the collection of stem cells from embryos destroys the embryo.
Some people have moral objections to this because they argue that embryos are living beings.
Additionally, harvesting stem cells from bone marrow is painful for the donor and there is a risk that the patient’s immune system will reject the donated cells.
88
red blood cells are also known as `
erythrocytes
89
what is the shape of an rbc and why is it beneficial
flattened biconcave shape which increases sa to v ratio so they can carry more o2
90
in mammals what do rbcs not have
nuclei or many other organelles which increases space for haemoglobin which carried o2
91
rbcs are also flexible so....
they can squeeze through narrow capillaries
92
chloroplasts in palisade cells can
absorb large amounts of light for photosynthesis and can move within cytoplasm in order to absorb more light
93
palisade cells are present in the
mesophyll
94
the vacuole in palisade cells..
is large to maintain turgor pressure and is rectangular so that things can be tightly packed around it to form a continuous layer
95
the cell wall in palisade cells is thick/thin.....and why
thin to increase ror
96
root hair cells have many
mitochondria to provide atp for active transport of minerals into the cell
97
where are rhc present
at the surface of roots near the growing tips, long extensions called root hairs which increases the sa of the cell to maximises uptake of water and minerals from the soil.
98
rhc have a large vacuole...
containing cell sap- solutions of ions and sugars which lowers water potential
99
How is eukaryotic DNA similar to prokaryotic DNA?
Their nucleotide structure is identical
Their nucleotides are joined by phosphodiester bonds
100
which has extrons and introns for pro and eu
eu dna has both
pro dna only has exons
101
Describe how chromosomes are formed.
First, DNA condenses into chromatin by wrapping tightly around histones. Then, this structure folds together to form a chromatid (one arm of a chromosome).
102
what is a telomere
103
One place DNA is found in eukaryotic cells is the nucleus.
Name two other organelles that contain DNA.
mitochondria and chloroplasts.
104
Some prokaryotes contain small, circular molecules of DNA called…
plasmids
105
compare the number of cell division and daughter cells from mitosis and meiosis
mitosis: 1 cell division and results in 2 daughter cells.
meiosis is 2 and 4
106
During meiosis I, chromosomes that carry the same genes pair up.
these pairs are called
homologous chromosomes
107
What happens during meiosis II? the sister ...
The sister chromatids move apart from each other to form two pairs of daughter cells.
108
During meiosis, sister chromatids are pulled to opposite poles of the cell.
anaphase 2
109
Pairs of homologous chromosomes line up along the equator of the cell.
Which stage of meiosis is this describing?
metaphase 1
110
Four nuclear envelopes form.
Which stage of meiosis is this describing?
telophase 2
111
explain how independent assortment gives rise to genetically varied gametes (2)
random arrangement of chromosomes
maternal and paternal chromosomes/chromosomes from homologous pairs
112
describe how crossing over gives rise to different combinations of alleles in gametes (2)
exchange of alleles
between non sister chromatids
113
Describe how crossing over in meiosis leads to genetic variation (3 things)
During meiosis 1, homologous chromosomes twist around each other. Then, portions of alleles are exchanged and this produces a new combination of alleles in each chromosome. `
114
Describe how independent assortment in meiosis leads to genetic variation (2 things)
During meiosis 1, the homologous chromosomes line up at random. This creates different combinations of chromosomes
115
Cells can specialise in a number of ways to increase the surface area to volume ratio.
Which of the following are examples of this kind of specialisation?
A reduction in the size of the cell
Extensions to the cell membrane, such as microvilli and root hairs
116
