Cell division Flashcards
(125 cards)
1
Q
cells can only be formed from?
A
existing cells
2
Q
when a new cell forms it goes through 3 stages before it can divide again. what are they?
A
synthesis of materials it will need
growth
reproduction to form new cells
3
Q
the forming of new cells is called
A
cell continuity
4
Q
cell continuity can be summarised in
A
the cell cycle
5
Q
what does the cell cycle describe
A
interphase and mitosis
6
Q
what is interphase
A
a cell’s state of non-division
7
Q
what is a state of mitosis
A
a cell’s state of division
8
Q
3 stages of the cell cycle
A
division of nucleus
division of cell
interphase
9
Q
the long part of the cell cycle
A
interphase
10
Q
the short parts of the cell cycle
A
division of nucleus
division of cell
11
Q
what occurs in the division of nucleus stage
A
mitosis
12
Q
what occurs in the division of cell stage
A
cytokinesis
13
Q
where are chromosomes found?
A
in the nuclei of the cells
14
Q
what are chromosomes made of
A
DNA and protein
15
Q
what does DNA stand for?
A
deoxyribonucleic acid
16
Q
in a cell that is not dividing the chromosomes are in what form?
A
in the form of chromatin
17
Q
what does chromatin look like
A
long, thin threads
18
Q
what happens to chromatin during cell division
A
it condenses to chromosomes
19
Q
what do chromosomes look like in comparison to chromatin?
A
shorter, thicker and clearly visible
20
Q
every organism has a distinct
A
number of chromosomes
21
Q
most human cells have how many chromosomes
A
46
22
Q
each chromosome contains what along its length
A
each chromosome contains many genes across its length
23
Q
what is a gene?
A
a section of DNA that codes for a particular protein
24
Q
how many genes on human chromosomes
A
over 30,000
25
2 things that genes control in humans
eye colour, blood groups etc
26
3 things that genes control in plants
height
flower colour
seed shape
27
Human genome project
the sequence of genes on human chromosomes has been mapped, this is the human genome project
28
how long has the human genome project taken?
10 years to complete it
29
genome
all the genes present in an organism
30
in most organisms chromosomes appear in
in pairs
31
how many pairs of chromosomes in humans
23
32
how many chromosomes in humans
46
33
diploid number of chromosomes represented as
2n
34
in humans, 2n =
46
35
diploid number
how many pairs of chromosomes an organism has
36
these pairs of chromosomes are called
homologous chromosomes
37
diploid cell
2 sets of chromosomes
38
haploid cells
cells that only have one set of chromosomes
39
2 cells in humans that are haploid cells
sperm cell
| egg cell
40
haploid cells represented by the symbol
n
41
in humans n=
23
42
2 types of cell division
mitosis
| meiosis
43
mitosis
when cells divide, one parent cell gives rise to 2 identical daughter cell
44
parent cell 2n=
4
45
daughter cells 2n =
4
46
body cells, every cell but reproductive cells
somatic cells
47
when does mitosis occur
in the growth and replacement of cells
48
somatic cells divide by
mitosis
49
2 examples of somatic cells
skin cells
| liver cells
50
in plants mitosis occurs in?
meristematic cells
51
where are meristematic cells found?
in the root tip and shoot tip
52
meristem
a zone of active cell division
53
reproduction by mitosis
some simple organisms reproduce asexually by mitosis
54
2 examples of organisms that can reproduce by mitosis
yeast and amoeba
55
preparation for mitosis down as
interphase
56
interphase
the phase between cell divisions during which the cell prepares for the next division
57
what happens during interphase
DNA replicates
58
during interphase each chromosome consists of
2 identical strands joined together at a point
59
2 identical strands joined together at a point
chromatids
60
centromere
where the 2 chromatids are joined together
61
what happens when DNA replicates itself
makes an exact copy of itself
62
why is the replication of DNA very important?
it allows genetic information to be passed fro one generation to the next
63
what also replicates
cell organelles e.g. mitochondria
64
why do cell organelles replicate?
to build up the cells energy store
65
what occurs when cell organelles replicate
protein synthesis occurs
66
4 stages of mitosis
prophase
metaphase
anaphase
telophase
67
length of prophase
usually the longest phase
68
what happens to chromatin during prophase
shortens to form chromosomes
69
when does DNA replicate
prior to prophase
70
what happens to the nuclear membrane during prophase
it disappears
71
what starts to form in prophase
spindle fibres start to form
72
what forms the spindle fibres
centrioles
73
what structure do the spindle fibres form
the spindle
74
what happens to the nucleolus during prophase?
it disappears
75
what is the function of the nucleolus
makes ribosomes
76
2 events of metaphase
1. the pairs of chromatids become attached to the spindle fibres at their centromeres
2. the pairs of chromatids line up across the middle of the spindle
77
other name for middle of the spindle
equator of the spindle
78
length of anaphase
this is a rapid phase
79
events of anaphase
the centromeres split into 2 and the spindle fibres contract and pull the chromatids to opposite ends of the cell. they are now chromosomes
80
what happens to chromosomes in telophase
when they reach the poles (ends) of the cell the chromosomes uncoil and become chromatin threads
81
what forms arounds the chromatin in telophase
new nuclear membranes
82
what happens to the nuclei in telophase
they reappear
83
cytokinesis
the division of the cell immediately after mitosis
84
what happens in animal cells during cytokinesis
a cleavage furrow appears which becomes deeper until it eventually divides the cytoplasm in 2
85
what happens in plant cells during cytokinesis
a cell plate is formed between the two new nuclei
86
cell wall formation during cytokinesis
a new cell wall forms on either side of the cell plate
87
what happens to the cell plate then during cytokinesis
becomes the middle lamella
88
function of middle lamella
cements the cells together
89
chromosomes in daughter cells
identical to each other and parent cells
90
cell resulting from mitosis have
identical genes
91
cells resulting from mitosis are called
clones
92
cancer
the uncontrolled division of cells (mitosis), producing abnormalities that are passed on to daughter cells
93
deaths in ireland from cancer
1 in 4 deaths
94
uncontrolled cell division produces
a mass of cells called a tumour
95
benign tumours
not life threatening
| do not invade other tissues
96
example of a benign tumour
warts
97
malignant tumours
invade other tissues and may be life threatening
98
what causes cancer
when normal genes are changed into cancer causing genes called oncogenes
99
cancer causing agents
carcinogens
100
what are responsible for bringing about changes to genes to become oncogenes
carcinogens
101
3 examples of carcinogens
UV radiation, cigarette smoke, some viruses
102
what do carcinogens do
they cause changes in the DNA (mutations) which can cause cancer
103
can cancers be cured
most cancers can be cured if they are caught and treated early
104
3 treatments for cancer
surgery to remove tumour
radiation to burn out the tumour
chemotherapy to slow down mitosis
105
4 ways to reduce the risk of cancer
do not smoke
eat a healthy diet
avoid sunburn
self examination for lumps on breasts/testes
106
meiosis
a form of cell division involving a reduction from the diploid number of chromosomes to the haploid number
107
meiosis is often called
a reduction division
108
why is meiosis often called a reduction division
because the number of chromosomes is halved
109
in meiosis parent cell
2n=4
110
in meiosis 4 daughter cells
n=2 and non identical
111
how does meiosis occur in animals
in the formation of gametes
112
gamete
a haploid sex cell capable of fusion with another sex cell
113
2 gametes
sperm cell
| egg cell
114
gametes formed by
meiosis
115
gametes formed by meiosis and are therefore
haploid
116
when is the diploid number of chromosomes restored in gametes
when fusion of gametes occurs during fertilisation
117
meiosis leads to
genetic variation in daughter cells
118
how many new cells (nuclei) formed in mitosis
2
119
how many new cells (nuclei) formed in meiosis
4
120
chromosome number in mitosis
stays the same
121
chromosome number in meiosis
is halved
122
daughter cells in mitosis
genetically identical to each other and to parent cell
123
daughter cells in meiosis
genetically different to each other and to parent cell
124
mitosis occurs in
haploid and diploid cels
125
meiosis occurs in
diploid cells only
