Mitosis, Meiosis and cell replication Flashcards
1
Q
What does mitosis replace?
A
Dead/damaged cells
2
Q
How does mitosis help organisms?
A
Growth in number of cells so organisms can get bigger
3
Q
What reproduction does mitosis occur in?
A
Asexual
4
Q
What does mitosis result in?
A
2 genetically identical daughter cells
5
Q
What are the benefits of mitosis?
A
- Quick
- Only 1 parent needed
- Alleles are identical
- Helps maximise optimal environmental factors
6
Q
What are the 3 stages of the cell cycle?
A
Interphase
Mitosis
Cytokinesis
7
Q
What are the 3 stages of interphase?
A
G1 phase
S phase
G2 phase
8
Q
When a cell is interphase, what can it still do?
A
Carry out all biological functions
9
Q
How much time does a cell spend in interphase?
A
About 90%
10
Q
What is the S phase?
A
Synthesis - DNA molecule replicates by semiconservative replication
11
Q
What is the G1 phase?
A
Getting all the raw material needed for DNA replication
It prepares for DNA replication
12
Q
What materials do we need for DNA replication that is prepared in the G1 phase?
A
DNA helicase
DNA polymerase
DNA nucleotides
Phosphates
Deoxyribose bases
ATP
13
Q
A
14
Q
What is the G2 phase?
A
Increasing subcellular structures (e.g. cytoplasm, phospholipids, ribosomes)
Preparing the cell to divide
15
Q
What is the protein that holds chromatids together after they have been replicated called?
A
Centromer - holds 2 genetically identical sister chromatids together
16
Q
What are the 4 phases of mitosis?
A
Prophase
Metaphase
Anaphase
Telophase
17
Q
What happens at the end of G2 phase in preparation for mitosis?
A
Centrioles mature and migrate to either pole of the cell
18
Q
What is mitosis?
A
The stage of the cell cycle where chromosome structures are visible
19
Q
What cannot happen during mitosis?
A
Protein synthesis
20
Q
What happens in prophase?
A
- Chromatin begins to shorten and thicken (coil)
- Forms visible chromosome structures
21
Q
What disappears during prophase?
A
The nuclear membrane
22
Q
Where is the equator of the cell?
A
The centre
23
Q
What do the chromosome structures do in metaphase?
A
Line up in a single file across the equator of the cell
24
Q
What do the centrioles do in metaphase?
A
Produce spindle fibres that extend and attach to the centromer
25
What do the spindle fibres do in anaphase?
They contract, pulling one of each genetically identical sister chromatid to either pole
26
What happens to the centromere in anaphase?
It has split
27
What happens to the chromatids in telophase?
- They unwind and become long and thin again
- Becomes a chromatin again
28
What happens to the nuclear envelope in telophase?
It reforms around the chromatin at each pole
29
What happens to the cell membrane in telophase?
- It folds inwards at the equator
- This creates a cleavage line
30
What happens in plant cells during telophase?
- Cell plates are formed
- This is the beginning of the cell wall
31
What happens in cytokinesis?
The cell membrane and sub-cellular structures divide, forming 2 genetically identical daughter cells (have the same genetics as each other and the parent cell)
32
What is the equation for the mitotic index?
No. cells undergoing mitosis / total no. cells visible
33
What does it mean if we have a higher mitotic index?
The faster the cell cycle is happening
34
What could a higher mitotic index indicate?
Cancer - but it depends what kind of cell it is
35
What is cancer?
- Due to uncontrolled cell division
- Occurs when the rate of cell multiplication is faster than the rate of cell death
36
What is cancer caused by?
Mutations to the genes involved in the regulation of mitosis and the cell cycle
37
What does treatment of cancer usually involve?
Blocking some part of the cell cycle - this disrupts the cell cycle and cell division
38
What could be an examples of a type of cancer drug?
Agents binding to DNA
Competitive inhibitors of enzymes involved in DNA replication
39
Can cancer drugs affect the cell cycle of normal cells?
Yes
40
Why are cancer cells more targeted by cancer drugs?
Since the drugs work more effectively against rapidly dividing cells, they are more susceptible
41
Why can cancer drugs also affect other cells in the body?
Some cells in the body, e.g. hair reproducing cells, also divide rapidly and so are vulnerable to damage
42
What does meiosis allow us to introduce?
Genetic variation as there is an exchange of alleles between parent genetics
43
Where does meiosis occur?
In the ovaries and testes
44
What does the diploid cell go through initially in meiosis 1?
Interphase
45
What happens in prophase 1 in meiosis?
- Chromosomes shorten and thicken
- Visible centrioles migrate to either pole of the cell
- Homologous pairs of chromosomes pair up
46
What can the homologous pairs do in prophase 1 in meiosis 1?
They can exchange alleles in a crossing over
Crossing over forms chiasma
47
What are the homologous pairs that exchange alleles in prophase 1 called?
Bivalents
48
How common is the formation of chiasma?
It is rare and random
49
What happens in metaphase 1 in meiosis?
- The chromosomes line up on the equator in their bivalent pairs
- the spindles attach to the chromosome
50
What can we introduce in anaphase 1 in meiosis?
Genetic variation by the independent segregation of chromosomes
51
What happens in anaphase 1 in meiosis?
- Centromere doesn't split when chromosomes migrate as spindles contract
- Whole chromosomes migrate to either pole
52
How does the independent segregation of chromosomes work in anaphase 1 in meiosis?
- The process of chromosomes migrating to either pole of the cell is random
- Which chromosome (from mum or dad) goes to which side is random
- We can have many different combinations
53
What happens in telophase 1 in meiosis 1?
- Genetic material becomes longer, thinner and turns into chromatins
- Nuclear envelope forms
- Cell membrane folds inwards
54
What happens in cytokinesis 1 in meiosis?
The cytoplasm, cell membrane and structures divide
55
What happens in prophase 2?
- Chromosome structures are visible
- Nuclear envelope disappears
- Centrioles migrate to poles
56
What happens in metaphase 2?
- Chromosomes line up in single file along the equator
- The spindles attach
57
What happens in anaphase 2?
- Spindles contract
- Centromere splits and 1 of each chromatid is pulled to either pole
58
What is there another chance for genetic variation in meiosis?
Anaphase 2
59
How is there a chance for genetic variation in anaphase 2 in meiosis?
We have the independent segregation of chromosomes which happens randomly
60
What happens in telophase 2 in meiosis?
- Genetic material unwinds and becomes chromatin
- Nuclear envelope reforms
- Cell membrane folds inwards forming cleavage line
61
What happens in cytokinesis 2 in meiosis?
Cytoplasm and organelles are split and the cell membrane forms new cells
62
What do we have at the end of meiosis?
- 4 cells known as a tetrad
- They are not genetically identical to each other or the parent cell
- They have half the genetic material of the parent cell
- They are haploid cells
63
What is non-disjunction?
The failure of chromosomes to separate and segregate into daughter cells due to the spindle fibres not working
64
What does non-disjunction cause?
An abnormal number of chromsomes in the daughter cells
65
When can non-disjunction occur?
In meiosis 1 or meiosis 2
66
How does non-disjunction occur in meiosis 1?
During anaphase 1, the chromosomes do not divide evenly to the 2 poles of the cell
67
How does non-disjunction occur in meisois 2?
During anaphase 2, the sister chromatids are not segregated equally to the 2 poles of the cell
68
When is non-disjunction more likely to occur?
As age increases as the spindle fibres begin to stop working
69
What is Binary fission?
The replication of bacteria as there are no chromosomes
70
What happens to the circular DNA at the beginning of binary fission?
It uncoils
71
What does the circular DNA do after it has uncoiled in binary fission?
Both strands attach to the cell membrane (using proteins) and replicate
72
How does the replicated circular DNA form 2 new DNA double strands in binary fission?
- DNA helicase breaks hydrogen bonds betwen strands
- DNA nucleotides sit in complimentary bae pairs opposite both strands
- DNA polymerase joins nucleotides together in a condensation reaction forming phosphodiester bonds
73
Do plasmids replicate as well in binary fission?
Any plasmids present will replicate as well as the stuff needed to replicate to prepare for splitting
74
What happens after the 2 new circular DNA's are fully formed in binary fission?
They are moved to the separate poles of the bacterium as the membrane increases
75
What happens after the circular DNA is moves to separate poles of the bacterium in binary fission?
- Growth of new cell wall starts
- New cell membrane fully develops
- Membrane folds inwards causing the cell to start to split
76
What happens once the membrane folds inwards and starts to split in binary fission?
DNA will recoil and ribosomes and plasmids will split between the two
77
What does the virus do to the surface of the cell it is going to invade?
It attaches to it
78
What happens after the virus attaches to the surface of the cell it is going to invade?
Their lipid envelope fuses with the cell membrane and their genetic material enters the cell
79
What does the RNA of the virus do once it is in the cell it is invading?
Using the RNA nucleotides of the cell, it replicates itself
80
What does the RNA of the virus contain?
Information on how to construct the protein capsid and attachment/antigen proteins
81
What happens once the RNA of the virus has replicated itself in the cell it has invaded?
The cell does translation and constricts the proteins of the virus
82
What happens once all the proteins of the virus have been constructed in the cell the virus has invaded?
The viruses are reconstructed using all the raw material in the cell
83
What happens once the viruses are reconstructed in the cell it has invaded?
It will then pinch off and leave the cell
84
What happens as the virus pinches off and leaves the cell?
It takes the cells membrane to form its lipid envelope and eventually, the host cell bursts
85
What are the 2 types of viral replication cycles?
Lytic - normal virus (e.g. flu)
Lysogenic - permanent virus (e.g. chicken pox)
86
What is the lysogenic cycle like?
It does all of the same things as the lytic cycle
87
What does the lysogenic cycle also bring with it?
Reverse transcriptase
88
What does the reverse transcriptase do in the lysogenic cycle?
It will create a single stranded replica of the viral DNA
89
What will happen to the single stranded replica of viral DNA that has been created in the lysogenic cycle?
The reverse transcriptase will use the replica and create a double stranded viral DNA
90
What will the double stranded viral DNA do in the lysogenic cycle?
It will move into the nucleus and attach to the DNA of the cell
91
Will the viral DNA remain in the DNA of the cell permanently?
Yes - it integrates into the DNA s when the cell undergoes mitosis, it replicates the viral DNA as well
92
How does the viral DNA affect the body given that it is there permanently?
It can remain dormant until the environment is suitable for it to replicate
