6. Cell Division Flashcards
1
Q
Stages of cell cycle
A
interphase
onuclear division (mitosis)
ocell division (cytokinesis)
2
Q
First phase
A
Interphase
3
Q
What make up interphase
A
0G1 phase oS phase
0G2 phase
4
Q
What happens in G1
A
cell grows in size.
DNA transcription happens.
Organelles are duplicated.
Protein synthesis occurs to make all enzymes and proteins needed for future stages.
5
Q
What happens in synthesis phase
A
synthesising DNA. replicate dna. All the chromosomes turn into x shape because they’re duplicated = sister chromatids.
6
Q
When do chromosomes look like x’s
A
When they’re ready to divide
7
Q
Shortest phase during interphase and why
A
S phase because dna replication increases chance of mutation because the dna is exposed
8
Q
What happens once a cell goes through s phase
A
It’s fully committed to cell division and it must occur
9
Q
What happens in G2
A
Cell continues to grow
proteins synthesis happens for the proteins and enzymes which will be needed in the m phase.
10
Q
Roles of mitosis
A
Growth and repair of tissues
Asexual reproduction
Production of new stem cells
11
Q
Outline metaphase
A
- chromosomes align on equator
- chromatids either side of equator
- spindle fibres attach to chromosomes at centromere
12
Q
Outline prophase
A
- chromosomes condense
- chromosomes have become visible
- nuclear envelope breaks down
- spindle fibres start forming
13
Q
Outline telophase
A
- nucleolus becomes visible + organelles distribute
- nuclear envelope forms around the new sets of chromosomes
- Chromosomes uncoil
14
Q
Outline anaphase
A
- spindle fibres contract
- chromatids separate and get pulled to opposite poles
15
Q
How does sexual reproduction lead to genetic variation in offspring
A
- genetic variation in variety of alleles
- offspring have alleles from more than one parent
- random fertilisation
- crossing over in prophase one = alleles swapped between non sister chromatids = base sequence of chromosomes altered
- independent assortment in metaphase 1 and 2
16
Q
Why does sexual reproduction. Usually occur in winter
A
- unfavourable conditions mean all offspring might die if asexual
- this way some may survive as they might have useful alleles
17
Q
Where does cell growth stop
A
Mitosis
18
Q
What is cytokinesis
A
when the cytoplasm divides into 2 to create 2 identical daughter cells.
19
Q
How is the cell cycle regulated
A
Checkpoints = • Specific proof-reading enzymes + repair enzymes are involved in this checking process
20
Q
G0 phase
A
optional resting phase. This is usually for cells that don’t want to replicate, they just stay in G0. Or if they’ve gone through G1 and don’t want to divide they just stay in G0. This is also a phase where cells can become differentiated.
21
Q
Checkpoints
A
where checks are happening to the dna to make sure everything is okay. Checks for any damage to the dna or mutations.
22
Q
What is the purpose of checkpoints
A
to prevent formation of tumours = cancer
23
Q
What happens if damage is found at a checkpoint
A
either repaired or the cell stops going through the cell cycle and apoptosis happens which is when the cell is killed.
24
Q
P53 gene
A
gene that suppresses tumours by controlling the checkpoints.
25
How many checkpoints
4
26
G1 phase checkpoint
chromosomes are checked for damage.
27
S phase checkpoint
chromosomes are checked to ensure they have been replicated.
28
G2 phase checkpoint
an additional check for DNA damage occurs after the DNA has been replicated.
29
Metaphase checkpoint
final check determines whether the chromosomes are correctly attached to the spindle fires prior to anaphase
30
Where are the main checkpoints = numbers
G1
S
G2
Metaphase
31
Stages of mitosis
prophase + metaphase + anaphase + telophase
32
Mitosis
process of nuclear division by which two genetically identical daughter nuclei are produced that are also genetically identical to the parent cell nucleus
33
Where does growth in plant occur
Meristem
34
How can root tip meristems be studies for mitosis
using the squash technique (root tips are stained and then gently squashed, spreading the cells out into a thin sheet and allowing individual cells undergoing mitosis to be clearly seen)
35
Method to view mitosis in plants
Method
• Garlic or onion (Allium cepa) root tips are most commonly used (the bulbs can be encouraged to grow roots by suspending them over water for a week or two)
Remove the tips of the roots (about 1cm) and place in a suitable stain (eg. warm, acidified acetic orcein, which stains chromosomes a deep purple)
• The stained root tip is gently squashed on a glass slideusing a blunt instrument (eg. the handle of a mounting needle)
• Cells undergoing mitosis are seen
36
What does prophase look like
Big blob mess
37
What does metaphase and anaphase look like
Metaphase = kinda see the chromosome lines
Anaphase = pulling apart
38
Limitations of method
It can be very difficult to distinguish between prophase and telophase in cells
• The size of cells or structures of tissues may appear inconsistent in different specimen slides
• Optical microscopes do not have the same magnification power as other types of microscopes and so there are some structures that can not be seen
• The treatment of specimens when preparing slides could alter the structure of cells
39
If there are multiple nuclei in one cell what stage is it in
Telophase
40
How is mitosis important in asexual reproduction
For unicellular organisms such as Amoeba, cell division results in the reproduction of a genetically identical offspring
• For multicellular organisms, new individuals grow from the parent organism (by cell division) and then detach ('bud off) from the parent in different ways
41
Asexual reproduction
the production of new individuals of a species by a single parent organism - the offspring are genetically identical to the parent
42
Examples of organisms with asexual reproduction
Yeast
43
The quicker the s phase...
The lower chance of mutations occurring
44
Graph for mass of DNA at each stage
45
Define meiosis
orm of nuclear division that results in the production of haploid cells from diploid cells - It produces gametes in plants and animals that are used in sexual reproduction
46
What is the consequence of a mutation on a tumour suppressant gene?
Increases peoples chances of tumours.
47
Hayflick constant
Every cell has a limit of how many times it can divide before it is completely dead = cell life
48
Cytokinesis in animal cells
cell membrane beginning to form furrows which go deeper and deeper inwards until eventually the sections connect and the cell is split into 2 identical daughter cells
49
Cytokinesis in plant cells
vesicles from the Golgi apparatus begin to assemble at the equator. These fuse with eachother and the cell surface membrane divides into 2 new sections
50
Diploid
46 chromosomes
51
Haploid
23 gametes
52
Prophase 1
- chromosomes shorten and thicken
- Nuclear envelope breaks down
- Centriole divides and moves to the opposite poles and the spindle fibre starts forming.
- Chromosomes come together in the homologous pairs
- Crossing over (homologous chromosomes can cross over)
53
Crossing over
- prophase 1
homologous chromosomes can cross over) this means that they exchange alleles between the non sister chromatid within a homologous pair . This means that the alleles shuffle over - opportunity to create genetic variation as the alleles can swap (happens in either prophase or metaphase) the amount of variation depends on the distance between the crossover points because there’s more variation the further apart the cross over happens
54
What does DNA look like in prophase 1
• DNA replication has already occurred so each chromosome consists of two sister chromatids joined together by a centromere
55
What is a bivalent
OA pair of homologous chromosomes
56
Metaphase 1
- homologous chromosomes line up along the equator
- Spindle fibre attaches to the centromere (middle of a chromosome)
- The maternal and paternal chromosomes in each pair position themselves
independently of the others = independent assortment
57
Independent assortment
maternal and paternal chromosomes in each pair position themselves independently of the others
58
Anaphase 1
- spindle fibres contract
- Chromosomes are pulled to the opposite ends
59
Telophase 1
chromosomes arrive at opposite poles
• Spindle fibres start to break down
• Nuclear envelopes form around the two groups of chromosomes + nucleoli reform
60
What do some plant cells do that's different to normal cels
• Some plant cells go straight into meiosis Il without reformation of the nucleus in telophase I
61
What are the sites where crossing over happens called
Chiasmata
62
What happens in cytokinesis 1
• division of the cytoplasm
• Cell organelles =. distributed between two developing cells
• The end product of cytokinesis in meiosis I is two haploid cells
63
Prophase 2
- chromosomes shorten and condense
- Nuclear envelope breaks down
- Centriole moves to the opposite poles
64
Metaphase 2
- chromosomes line up along the equator
- Spindle fibres attach to the centromere of the chromosomes
65
Anaphase 2 nt
- Chromatids are pulled apart to opposite poles by spindle fibres (spindle fibres contract
- The chromatids going to either side
66
Telophase 2
- nuclear envelope starts forming
- Creates 4 haploid cells
67
Significance of meiosis
increase the genetic diversity of gametes produced
68
Genetic diversity in meiosis
• crossing over
• independent assortment
• random fusion of gametes
• mutations ( not strictly meiosis)
69
Crossing over
process by which non-sister chromatids exchange aleles
70
When does independent assortment happen
Metaphase 1 + 2
71
How to work out the number of different possible chromosome combinations = independent assortment
2n can be used, where n corresponds to the number of chromosomes in a haploid cell
72
How do mutations increase genetic diversity
random mutation that takes place during DNA replication can lead to the production of new alleles and increased genetic variation.
73
Function of erythrocytes
transport oxygen around the body and carbon dioxide to the lungs
74
Adaptions of erythrocytes (3)
biconcave in shape which increases the surface area over which oxygen can be absorbed
o cytoplasm contains high amounts of the pigment haemoglobin which can readily bind to oxygen
o No nucleus = makes more space inside the cell for haemoglobin molecules for
maximum oxygen-carrying capacity
75
Function of neutrophils
destroy pathogens by phagocytosis and the secretion of enzymes
76
Adaptations of neutrophils
Lobed nucleus= allows them to squeeze through cell junctions in the capillary wall
Many lysosomes = digestive enzymes help to digest and destroy
invading cells
Many mitochondria
77
Function of squamous epithelial cells
provide a surface covering or outer layer.
Found on a variety of organs and structures e.g. blood vessels and alveoli
78
Adaptations of squamous epithelial cells
o layer forms a thin cross-section which reduces the distance that substances have to move to pass through - it shortens the diffusion pathway
o It is permeable, allowing for the easy diffusion of gases
79
Function of ciliated epithelial cells
moving substances across the surface of a tissue
80
Adaptations of ciliated epithelial cells
Have cilia = move in rhythm to move mucus + trapped pathogens from lungs
• Goblet cells secrete mucus = trap dust, dirt and microorganisms - preventing them from entering vital organs where they may cause infection
81
Function of sperm cells
reproduction - to fuse with an egg, initiate the development of an embryo and pass on fathers genes
82
Adaptations of sperm cells
- Loads of mitochondria to provide energy that is needed to move the tail towards the egg
- Specialised enzymes (digestive enzymes) in the acrosome to digest the egg
- Long and thing so they can move easily
83
Unspecialised cells
all the genes are switched on = Initially cells have the ability of becoming any cell
84
Pros of differentiating
when certain genes are switched off, some are expressed more = in doing so the number of organelles change, the shape of the cell changes, the content of the cell changes
85
Palisade cell function
carry out photosynthesis to produce glucose and oxygen
86
Adaption of palisade cells
- Long and cylindrical so they can pack together quite well, allowing short diffusion for carbon dioxide and oxygen
- Loads of chloroplast to carry out photosynthesis
- Large vacuole which allows chloroplast to be pushed to the edges = easy access to sunlight
87
Function of root hair cell
absorption of water and mineral ions from soil
88
Adaptations of root hair cells
Root hair = increase SA = rate of water uptake by osmosis is greater
o Thinner walls = water can move through easily (due to shorter diffusion
distance)
o Mitochondria for active transport of mineral ions
89
Function of guard cells
control the opening of the stomata to regulate water loss and gas exchange
90
Adaptations of guard cells
- Control the opening and closing of the stomata by either swelling up or losing water
- Lots of mitochondria for active transport
- Have chloroplast but can’t photosynthesise because they don’t have the enzymes for the later stages
91
Tissue
group of cells that work together to perform a specific function
92
What forms the epithelial tissue
Epithelial cells = function = absorb food in small
intestine
93
Squamous epithelial
Thin and found in exchange surfaces which need short diffusion distances (alveoli
94
Ciliated epithelial
In areas to prevent entry of pathogens and move mucus e.g. in the lungs (trachea) because they move substances along
95
Organ
a group of tissues that perform together for a specific function
96
Organ system
groups of organs that perform together for a function
97
Heart as an organ is made up of what
cardiac muscle tissue, blood vessel tissues and
connective tissue
98
Connective tissues
Connect structures together and provide support e.g. cartilage, bones
99
3 types of cartilage
Hyaline
Fibrous
Elastic
100
Cartilage function
prevent things from collapsing = provides support + holds structures together
101
Function of xylem cells
transport water for tissue and dissolved ions
102
Adaptations of xylem cells
o No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration
o Cells are essentially dead, without organelles or cytoplasm, to allow free movement of water
o Outer walls are thickened with a substance called lignin, strengthening the tubes, which helps support the plant
103
Function of phloem cells
Transport of dissolved sugars and amino acids
104
Adaptations of phloem cells
Made of living cells which are supported by companion cells
o joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes that allow sugars and amino acids to flow easily through (by translocation)
o have very few subcellular structures to aid the flow of materials
105
Function of muscle cells
Contraction for movement
106
Adaptations of muscle cells
have layers of protein filaments in them, these layers can slide over each other causing muscle contraction
o have a high density of mitochondria to provide sufficient energy (via respiration) for muscle contraction
o Skeletal muscle cells fuse together during development to form multinucleated cells that contract in unison
107
3 types of muscle in animal
- skeletal muscles
- Cardiac muscles
- Smooth muscles
108
Hyaline cartilage
Found on the outside of bones and prevents bones from rubbing together and creating friction
109
Fibrous cartilage
Mainly between discs and the back and in the knee joints
110
Elastic cartilage
Soft cartilage
111
Stem cells
Cells that can divide by mitosis an unlimited number of times
112
Potency
ability of stem cells to differentiate into more specialised cell types
113
3 types of potency
Totipotent
Pluripotent
Multi potent
114
Totipotency
stem cells that can differentiate into any cell type found in an embryo, as well as extra-embryonic cells
115
Pluripotent
embryonic stem cells that can differentiate into any cell type found in an embryo but are not able to differentiate into extra-embryonic cells
116
Multipotency
adult stem cells that have lost some of the potency associated with embryonic stem cells and are no longer pluripotent
117
Adult stem cells
small numbers of stem cells remain to produce new cells for the essential processes of growth, cell replacement and tissue repair
118
What are adult stem cells
Multi potent
119
Stem cells in bone marrow
Multi potent - only differentiate into blood cells
120
Chondrocytes
Mature Cells involved in cartilage tissues
121
Chondroblasts
Immature cells involved in cartilage tissues
122
Meristem cells
Stem cells in plant
123
What can stem cells be used to repair
- damaged tissues specifically in neurological conditions (e.g. Alzheimer’s and Parkinson’s both are caused by the degeneration of the nerve cells so the treatment is to create these nerve cells in the lab and then put them back into the patient)
- diabetes to make new pancreatic cells
124
Stem cells in drug research
where stem cells can be turned into the type of human tissue you want. Drugs can be tested on those instead of animals
125
Induced pluripotent stem cells
Induce normal cells to create stem cells in labs
126
Where are stem cells found in plants
Stem cells are found in the meristem tissue = tip of root and shoot of plants
127
Cambium
xylem and phloem are formed from stem cells that are found in the tissue
between them = tissue = cambium
128
What is cambium
A meristem
129
Meristem
any undifferentiated tissue in a plant that has the ability to give rise to new cells
130
Changes that occur when differentiating into xylem
Cell elongation, deposit lignin and end walls break down
131
Changes that occur when differentiating into phloem
lose some of their cytoplasm and organelles, and develop sieve plates
132
When are embryonic stem cells totipotent
if taken in the first 3-4 days after fertilisation
133
When are embryonic stem cells pluripotent
if taken on day 5
134
Why is there ethical objections to using embryonic stem cells as research
embryos have the potential to develop into human
beings
135
A
136
A
137
D
138
B
139
D
140
ii
141
ii
142
143
ii
144
Suggest why Hydra reproduces asexually when conditions are favourable
genetically identical offspring v
offspring produced , rapidly / in large numbers V
(all) offspring will, find conditions favourable / have same adaptations
145
Draw metaphase
146
147
Why would the student T-test not be suitable
148
149
Draw anaphase
150
ii
151
Explain how the organisation of homologous chromosomes during metaphase 1 increases genetic variation.
152
153
154
45. Plant growth requires the production of new xylem cells.
Describe how new xylem cells are produced.
155
156
157
Explain the difference between muscle tissue and a muscle.
muscle tissue is a group of cells which contract together (1)
a muscle is an organ that consists of muscle tissue and other (named)
tissues working together (1)
158
159
Explain why a plant leaf is described as an organ.
160
161
162
163
164
Explain why the cells of the inner cell mass are not totipotent stem cells.
165
Do all of the questions 😠
166
ii
167
168
Name two potential sources of human stem cells and for one source, describe an ethical issue associated with the use of stem cells.
169
170
Explain why erythrocytes do not make use of any of the oxygen that they are transporting.
171
172
What events occur during the cell cycle that lead to daughter cells being genetically identical:
- checkpoints - explain
- S phase - semi conservative replication
- Anaphase: each nucleus would have same set of info when the chromosomes split
