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AQA A level Biology > 2.2 Cell division and mutation > Flashcards

2.2 Cell division and mutation Flashcards

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1
Q

What is the cell cycle

A

The sequence of events (dividing and non-dividing) stages in the life of a cycle

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2
Q

What are the 3 stages in the cell cycle

A
  • Interphase
  • Nuclear division
  • Cytokinesis
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3
Q

What is a chromosome

A

Condensed chromatin which has coiled

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4
Q

What is chromatin

A

Double helix of DNA that has wrapped around histone proteins

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5
Q

What is present in diploid cells but not in haploid cells

A

Homologous pairs

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6
Q

What is the common name for somatic cells

A

Body cells

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7
Q

What is mitosis

A

Nuclear division in eukaryotic cells

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8
Q

When a cell undergos mitosis, what is produced

A

2 GENETICALLY identical daughter cells

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9
Q

What stays the same in mitosis

A

The number of chromosomes

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10
Q

What are the 6 stages of cell division, mitosis

A
  • Interphase
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase
  • Cytokinesis
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11
Q

In what phase of mitosis, does cell growth occur

A

Interphase

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12
Q

In what stage of mitosis, are the chromosomes not visible

A

Interphase

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13
Q

In what stage of mitosis, are organelles synthesised

A

Interphase

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14
Q

In what stage of mitosis, is ATP synthesised

A

Interphase

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15
Q

In what stage of mitosis, does DNA replication occur

A

Interphase

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16
Q

In what stage of mitosis, do the centrioles move to opposite poles of the cell

A

Prophase

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17
Q

In what stage of mitosis, do the chromosomes condense and become visible as 2 sister chromatids joined by a centromere

A

Prophase

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18
Q

In what stage of mitosis, do spindle fibres develop from each pair of centrioles to span the cell from pole to pole

A

Prophase

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19
Q

In what stage of mitosis, do the chromosomes attach to spindle fibres by their centromere

A

Prophase

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20
Q

In what stage of mitosis, does the nucleolus disappear

A

Prophase

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21
Q

In what stage of mitosis, does the nuclear envelope break down so chromosomes are free in the cytoplasm

A

Prophase

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22
Q

In what phase of mitosis, are chromosomes pulled along the spindle apparatus and arrange themselves across the equator of the cell

A

Metaphase

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23
Q

In what phase of mitosis, do the centromeres divide in 2

A

Metaphase

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24
Q

In what stage of mitosis, do the spindle fibres contract and shorten pulling sister chromatids apart

A

Anaphase

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25
Q

In what stage of mitosis, do mitochondria located around the spindle fibres provide ATP for their contraction

A

Anaphase

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26
Q

In what stage of mitosis, are the chromosomes pulled to opposite poles

A

Anaphase

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27
Q

In what stage of mitosis, do chromosomes reach their respective poles

A

Telophase

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28
Q

In what stage of mitosis, does the nuclear envelope and nucleoli reform

A

Telophase

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29
Q

In what stage of mitosis, do the spindle fibres disintegrate

A

Telophase

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30
Q

In what phase of mitosis, do the chromosomes elongate becoming less visible

A

Telophase

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31
Q

In what phase of mitosis, does the cell membrane pinch inwards separating cytoplasm

A

Cytokinesis

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32
Q

In what phase of mitosis, does the cytoplasm divide to produce 2 new cells

A

Cytokinesis

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33
Q

What are the 3 mains importance of mitosis

A
  • Growth
  • Tissue repair
  • Asexual reproduction
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34
Q

When looking at a diagram, how do you tell the difference between interphase and prophase of the cell cycle

A

The majority of the cells will be in interphase so whatever cell is shown more is in interphase

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35
Q

What is an advantage of having offspring that are genetically identical to their parents

A

In stable/ unchanged environments successful parents can rapidly produce successful offspring

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36
Q

What is a disadvantage of having offspring that are genetically identical to their parents

A

More vulnerable to changing environments because there is no genetic diversity

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37
Q

What is the mitotic index

A

The ratio of the number of cells undergoing mitosis to the total number of cells

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38
Q

During the root tip squash experiment, why do we use the root tip

A

It’s the growing region- where mitosis happens

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39
Q

During the root tip squash experiment, why is the acetic orcein stain necessary

A

To make the DNA visible- therefore making the chromosomes visible to view mitosis activity

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40
Q

During the root tip squash experiment, the HCl softens the walls, why is this necessary

A

So stain can enter the cells

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41
Q

During the root tip squash experiment, why is the hot plate a necessary

A

Speeds up the softening of the wall and speeds up the movement of the stain

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42
Q

During the root tip squash experiment, why is squashing the root tip necessary

A

It flattens the tip to make it a single layer of cells in order to view them on a microscope

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43
Q

During binary fission, once the circular DNA has replicated what do both copies attach to

A

The cell membrane

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44
Q

Do plasmids replicate

A

Yes

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45
Q

What is formed from binary fission

A

2 identical daughter cells, each with a single copy of circular DNA and a variable number of plasmids

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46
Q

What allows viruses to attach to host cells

A

Attachment proteins

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47
Q

Once a virus have attached to the host cell, what do they inject into the cell

A

Their nucleic acid

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48
Q

What does the host cell read from the injected viral nucleic acid

A

The genetic code

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49
Q

After the host cell has read the genetic code from the viral nucleic acid, what does the host cell begin to do

A

Produce viral components: nucleic acids, enzymes, structural proteins

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50
Q

After the viral components have been produced by the host cell, what does these components do

A

Assemble into new viruses

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51
Q

What does apoptosis mean

A

Controlled cell death

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52
Q

When does apoptosis occur

A

When a cell mutates, it then dies to stop the replication of a mutated cell

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53
Q

What are the 2 factors that control cell division in healthy cells

A
  • Majority of differentiated cell don’t divide
  • Apoptosis (controlled cell death)
54
Q

What causes cancer in terms of cells

A

Result of uncontrolled mitosis

55
Q

When do the chromosomes condense

A

During prophase

56
Q

What happens in anaphase

A

Chromatids are pulled apart

57
Q

What does the phrase reduction division refer too

A

Meiosis

58
Q

What happens to the number of chromosomes during meiosis

A

They halve

59
Q

How many consecutive divisions are there in meiosis

A

2

60
Q

After interphase during meiosis, what is separated in the first division

A

Separation of bivalents

61
Q

During meiosis, what are the products from the first division

A

2 haploid daughter cells

62
Q

In the 2nd division stage of meiosis, what is separated

A

Separation of sister chromatids

63
Q

What is produced from the 2nd division on meiosis

A

4 haploid daughter cells

64
Q

During meiosis I, what is the behaviour of the chromosomes during prophase, and how does this differ from prophase of mitosis

A

Chromosomes condense and become visible, arranged as bivalent.
Whereas mitosis, the chromosomes only become visible and not arranged as replicated homologous pairs (bivalent)

65
Q

During prophase of meiosis I, the chromosomes are visibly arranged as bivalent, what may this lead to

A

Crossing over

66
Q

During metaphase of meiosis I, what is the behaviour of the chromosomes

A

Bivalents align at equator of spindles

67
Q

During anaphase of meiosis I, what are separated, and how is this different from mitosis

A

Bivalents are separated
Whereas in mitosis it’s the sister chromatids

68
Q

Is the chromosome behaviour for meiosis II, the same as mitotic behaviour or meiosis I behaviour

A

Mitotic behaviour

69
Q

What is the comparative statement, mitosis produces 2 daughter cells whereas

A

Meiosis produces 4 daughter cells

70
Q

What is the comparative statement, mitosis involves 1 cell division whereas

A

Meiosis involves 2 consecutive cell divisions

71
Q

What is the comparative statement, mitosis produces somatic cells whereas

A

Meiosis produces gametes

72
Q

What is the comparative statement, mitosis produces diploid daughter cells whereas

A

Meiosis produces haploid daughter cells

73
Q

What is the comparative statement, the number of chromosomes during mitosis remains the same whereas

A

During meiosis the number of chromosomes is halved

74
Q

What is the comparative statement, mitosis produces genetically identical daughter cells whereas

A

Meiosis produces genetically unique daughter cells

75
Q

What is the comparative statement, mitosis is used for growth and repair whereas

A

Meiosis is used for sexual reproduction

76
Q

What are the 2 significances of meiosis

A
  • Produces haploid gametes
  • Produces genetic variation
77
Q

What are the 3 ways in which meiosis produces genetic variation

A
  • Random fertilisation
  • Independent segregation
  • Crossing over
78
Q

How does the random fusion of gametes (random fertilisation) allow for genetic variation

A
  • Each parent is genetically different
  • Each parent produces thousands of genetically unique gametes
  • At fertilisation, the zygote has unique combination of alleles
79
Q

What happens to the chromosomes when they condense so that they become shorter and fatter

A

They coil and super coil

80
Q

Why does crossing over occur during prophase I

A

Since the chromosomes are visible and arranged as bivalents, and when they condense they super coil and due to them being close together the 2 chromosomes in each homologous pair can get tangled

81
Q

What is the name of the product when non-sister chromatids in a bivalent cross over

A

Chiasma

82
Q

When does crossing over during meiosis matter

A

When the alleles are different in the bivalent- if the alleles are the same then swapping of genetic information would not matter

83
Q

When crossing over occurs during meiosis, what is the name of the chromosomes produced when the chromosomes have a different combination of alleles that isn’t present in either parent

A

Recombinant chromosomes

84
Q

What are 2 other names for independent segregation

A
  • Independent assortment
  • Random assortment
85
Q

What is the equation for the number of possible chromosome combinations - independent segregation topic

A

2 ^ (number of pairs present)

e.g. if there were 3 pairs in a cell then it would be 8= 2^3

86
Q

Describe the term recombinant

A

A cell/ organism whose genetic material was produced when segments of DNA from different sources are joined

87
Q

Describe the term independent assortment

A

The random alignment of bivalents in metaphase I

88
Q

Describe the term homologous pairs

A

2 chromosomes with the same gene loci

89
Q

Describe the term non-disjunction

A

The failure of homologous pairs to separate in meiosis

90
Q

Describe the term crossing over

A

Chromatids within a pair become twisted around one another when condensing in prophase I

91
Q

Describe the term bivalent

A

A pair of chromosomes with the same gene loci after DNA replication has occurred

92
Q

Describe the term haploid

A

A cell/ organism containing a single set of chromosomes

93
Q

Name the term that increase the chance of a mutation

A

Mutagenic agent

94
Q

What causes a mutation

A

Nothing they are SPONTANEOUS and RANDOM

95
Q

Why are mutation good

A

They provide genetic variation which is important so at least one individual can survive a change ins the environment

96
Q

Are most mutation recessive

A

Yes

97
Q

How common are beneficial mutations

A

Rare

98
Q

What are the 2 types of mutations

A
  • Point mutation
  • Chromosome mutation
99
Q

What is a point mutation

A

A change in the DNA base sequence

100
Q

Why does a point mutation effect the organism - protein structure

A

It alters the amino acid sequence which alters the primary structure - altering the tertiary structure which can change the function or stop it from functioning at all

101
Q

During which part of the cell cycle do point mutations occur

A

In interphase during DNA replication

102
Q

What is a chromosome mutation

A

A change in the number of chromosomes

103
Q

When do chromosome mutation occur during the cell cycle

A

During anaphase in meiosis

104
Q

What is a substitution mutation

A

A base is substituted with another one

105
Q

If a base is substituted with another base but they both code for the same amino acid, what is the name of the mutation

A
  • A silent mutation
    OR
  • A mutual mutation
106
Q

What is and insertion mutation

A

Adding in extra bases

107
Q

What is a frameshift mutation

A

When every codon downstream of the mutation will change, potentially every amino acid downstream - so potentially a great effect on the primary structure of the protein

108
Q

What is a deletion mutation

A

Deleting bases

109
Q

What is a duplication mutation

A

Adding in an extra base that is the same base as the one that came before
e.g. adding T after a T

110
Q

What is an inversion mutation

A

When the bases become separated from the DNA and rejoin the same place but with a different order

111
Q

What is a translocation mutation

A

A group of base gets separated from the DNA sequence from a chromosome and gets inserted in the DNA sequnce in another chromosome

112
Q

What are the 3 types of point mutation, where a frameshift occurs

A
  • Insertion
  • Deletion
  • Duplication
113
Q

What are the 2 possible results from a chromosome mutation

A
  • Polysomy
  • Polyploidy
114
Q

When does polysomy occur - after chromosome mutation

A

It occurs when one homologous pair fails to separate in a process known as non-disjunction

115
Q

When does polyploidy occur- after chromosome mutation

A

When all homologous pairs fail to separate so all end up in the gametes - this is unique to plants

116
Q

What phase in the cell cycle do chromosome mutation occurs

A

In anaphase during meiosis

117
Q

When non-disjunction occurs in gene 21, how many sets of chromosomes are in the final cell

A

3 - its triploid

118
Q

What is the proper name of the triploid chromosome 21 cell called - when the organism has down’s syndrome

A

Trisomy 21

119
Q

When a non-disjunction cell separates, what happens to the zygote where there are no chromosomes in one of the gametes

A

Death
Monosomy 21

120
Q

What are the 3 categories of mutagens

A
  • Physical
  • Biological
  • Chemical
121
Q

Name an example of a physical mutagen

A

Ionising radiation alpha and beta particles

122
Q

Name an example of a biological mutagen

A

Viruses

123
Q

Name an example of a chemical mutagen

A

Benzopyrene in tobacco smoke

124
Q

Define the term mutagenic mutations

A

A factor that increases the rate of mutations

125
Q

Why does random fusion of gametes increase genetic variation

A

Since there’s a new allele combination

126
Q

Define gene mutation

A

Change in the base/ nucleotide sequence of chromosomes/ DNA
&
results in the formation of new alleles

127
Q

Explain how a gene mutation can have no effect on an individual

A

Genetic code is degenerate
Does change amino acid but no effect on tertiary structure

128
Q

Explain how a gene mutation can have a positive effect on an individual

A
  • Results in change in polypeptide that positively changes the properties
  • May result in increased survival
129
Q

Explain how the chromosome number is halved during meiosis (2 marks)

A
  • Homologous chromosomes
  • One of each pair goes to each daughter cell
130
Q

Describe the process of crossing over and explain how it increases genetic diversity ( 4 marks)

A
  • Homologous pairs of chromosomes form a bivalent
  • Chiasmata forms
  • Equal length non-sister chromatids are exchanged
  • Producing new combination of alleles
131
Q

Explain why all body cells will experience the mutation if the mutation is in an egg cell (2 marks)

A
  • Mutation chromosome in gamete
  • All cells derived from zygote by mitosis
  • Mitosis produces genetically identical cells
132
Q

Describe the appearance and behaviour of chromosomes during prophase and during anaphase of mitosis (4 marks)

A

In prophase
- Chromosomes continue to condense
- Chromosomes are visible
- Chromosomes attach to spindle fibres

In anaphase
- Centromeres divide
- Chromosomes pulled to opposite poles

AQA A level Biology (35 decks)

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