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A-Level Biology > Genetics Yr13 > Flashcards

Genetics Yr13 Flashcards

1
Q

What is a gene mutation?

A

A change in one or more nucleotide base or change in sequence of bases

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2
Q

What are the two types of mutations?

A

Gene mutation

Chromosome mutation

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3
Q

What is polyploidy?

A

3 or more sets of chromosomes

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4
Q

What is non-disjunction?

A

When homologous pairs fail to separate during meiosis

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5
Q

What is substitution?

A

Nucleotide base is replaced with a different nucleotide with a different base

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6
Q

What are the three possible outcomes of substitution?

A

Stop codon formed
Different amino acid formed
Different codon produced but codes for same amino acid

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7
Q

What does it mean if a stop codon is formed in substitution?

A

Polypeptide formation stopped prematurely

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8
Q

What does it mean if a different amino acid is formed in substitution?

A

Polypeptide different by one amino acid

Active different shape

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9
Q

What does it mean if a different codon is produced but codes for same amino acid in substitution?

A

Degenerate

No effect

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10
Q

What is deletion?

A

Nucleotide base has been removed from the sequence

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11
Q

What will deletion cause?

A 
Frame shift (left)
So all amino acids are different
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12
Q

How can the effect of deletion be made worse?

A

If deleted base is at beginning of sequence

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13
Q

What is the effect of adding a base?

A

Frameshift (right)

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14
Q

What happens if three bases are added to the sequence?

A

= no effect as no frameshift

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15
Q

What is the effect of duplicating a base?

A

Frameshift

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16
Q

What is inversion?

A

A group of bases separate from the sequence + re-join sequence in some place BUT in inverse order

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17
Q

What is translocation?

A

Group of bases separate from one chromosome + joins the other

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18
Q

What does translocation between chromosome 9 and 22 cause?

A

Leukaemia

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19
Q

What does translocation cause?

A

Marked effect

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20
Q

Is translocation a mutation?

A

YES

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21
Q

Is crossing over a mutation?

A

NO

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22
Q

Why is translocation a mutation?

A

Change in genetic information between non-homologous chromosomes

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23
Q

Why isn’t crossing over a mutation?

A

Swaps genetic material BUT homologous chromosomes unchanged

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24
Q

What are the causes of mutations?

A

Spontaneous = no outside factors
During replication
Natural mutation rate - 1 or 2 per 100,000 genes/ generation

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25
Q

What can mutagenetic reagents cause?

A

Natural mutation rate to increase

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26
Q

What are some mutagenetic reagents?

A

Chemicals - NO2 + benzopyrene

High energy ionising radiation - Alpha, beta, X-rays + UV

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27
Q

What does NO2 + benzopyrene do?

A 
NO2 = affect transcription
Benzopyrene = inactivates tumour suppressor gene
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28
Q

What is differentiation?

A

The process by which cells develop special structures needed to carry out specific role

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29
Q

What do multicellular organisms require?

A

Specialised cells to carry out specific functions

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30
Q

What are stem cells?

A

Undifferentiated cells that can divide into any cell

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31
Q

What is self-renewal?

A

The ability to go through numerous cycles of cell division while maintaining the undifferentiated state

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32
Q

Where do you find stem cells?

A

Embryonic - flexible
Adult tissues - non-flexible
Specific to tissue/organ ^^^

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33
Q

What are totipotent stem cells?

A

Can produce all cell types (embryo + placenta)

Only present during 1st few cell divisions

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34
Q

What are pluripotent stem cells?

A

Can become any body cell in embryo

BUT not placenta

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35
Q

Why are pluripotent used in medicine?

A

Can divide in unlimited numbers

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36
Q

What are multipotent stem cells?

A

Found in adults
Give rise to different types of specialised cells
BUT restricted to certain organs/tissue types

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37
Q

What are unipotent stem cells?

A

Found in adults

Make only one type of cell

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38
Q

Why are embryonic cells important?

A

Differentiate into any type of cell

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39
Q

What males a cell become specialised?

A

Different gene expressed

So only some DNA translated to proteins

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40
Q

Do all body cells make all the products they are genetically capable of?

A

No = waste resources unfavourable

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41
Q

How is gene expression controlled?

A

Some permanently expressed
Some never expressed
Some switch on + off

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42
Q

How are genes prevented from expressing themselves?

A

Prevent transcription

Breakdown of mRNA before translation

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43
Q

What are cardiomyocytes?

A

heart muscle cells

That can be replaced by unipotent stem cells when damaged

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44
Q

What is myocardial infraction?

A

Heart attack when coronary arteries are blocked

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45
Q

What impact does myocardial infraction have?

A

No blood flow = cells die

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46
Q

How do cardiomyocytes help with myocardial infraction?

A

Inject into damaged area = regenerate them when differentiate

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47
Q

How are embryonic stem cells used?

A

Cells taken from early stages of embryo
Grown in vitro
Induced to develop into tissues

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48
Q

What can embryonic stem cells be used for?

A 
Burns
Parkinson's disease
Nerve damage 
Diabetes 
Heart disease
Cancer
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49
Q

What are iPS cells?

A

Type of induced pluripotent cell that is produced from unipotent cells

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50
Q

How are iPS cells created?

A

Genetically modified in a lab
To make them acquire characteristics of embryonic stem cells
Need to induce gene + transcriptional factors to turn genes that were off on

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51
Q

What does iPS cells show since they can be reactivated?

A

They retain the same info present in the embryo

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52
Q

What is interesting about iPS cells?

A

Capable of self-renewal
Very flexible
Potentially divide to provide limitless supply

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53
Q

How could iPS cells be useful?

A

Could replace embryonic stem cells in medicine + research

= overcome ethical issues

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54
Q

Do plants have stem cells?

A

YES

Mature plants have totipotent stem cells = them to form clones of single cells

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55
Q

What are the arguments for stem cells?

A

Cure debilitating diseases
Wrong to allow suffering when it can be relieved
Embryos created for IVF so why not stem cells
Legislation in place to stop risk with research
Embryos less than 14 days not recognised as human
Adult stem cells not as suitable

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56
Q

What are the arguments against stem cells?

A 
Potential human life
Deserves same respect as adult human
Could lead to cloning humans
Undermines respect for life
Adult stem cells = available alternative so research should be directed towards them
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57
Q

What are the basics of gene expression?

A

Transcription has to occur
pre-mRNA spliced
Translation has to occur

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58
Q

What do protein hormones do?

A

Help in gene expression

Act via 2nd messenger

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59
Q

What do lipid-soluble hormones do?

A

Act directly

Regulate transcription + translation

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60
Q

What is an example of a lipid-soluble hormone?

61
Q

What must happen for transcription to happen?

A

Genes be “switched on”

62
Q

What are transcription factors?

A

Regulatory proteins that control what is “switched on”

63
Q

Where do transcription factors move?

A

Cytoplasm —-> nucleus

64
Q

What does a transcription factor have?

A

DNA binding site

65
Q

What is a transcription factor attached to?

A

Receptor with hormone binding site

66
Q

What is the DNA binding site specific to?

A

To the gene

67
Q

What happens when the transcription factor binds to the correct region of DNA?

A

Transcription begins = produced mRNA

68
Q

What happens if the gen is not expressed?

A

DNA binding site blocked = transcription stopped

69
Q

What happens with the lipid-soluble hormone?

A

Oestrogen diffuses across phospholipid bi-layer
It binds to transcription factor receptor subunit
Oestrogen causes transcription factor to change shape
TF binds to DNA strand = transcription begins

70
Q

How did Darwin and Lamarck’s theory differ?

A 
Lamarck = environmental factors then passed to offspring
Darwin = natural selection
71
Q

What is epigenetics?

A

How environmental influences can alter genetic inheritance

72
Q

Which environmental factors are thought to influence the genetic inheritance of an organisms offspring?

A

Diet
Stress
Toxins

73
Q

What are the possible uses of studying epigenetics?

A

Therapeutic
Provide cures
Understand genetics behind cancer

74
Q

What are histones?

A

Protein molecules that are rich in chemicals + bind tightly to negatively-charged phosphates in DNA

75
Q

What do histones help to form?

A

Chromosomes

76
Q

What is the epigenome?

A

Layer of chemical tags that cover histones

77
Q

What does the epigenome determine?

A

Shape of DNA-histone complex

78
Q

How does the epigenome determine the shape of the DNA-histone complex?

A

By keeping genes that are inactive in a tight arrangement so they cannot be read

79
Q

What is the difference between DNA code and the epigenome?

A

DNA is fixed whereas the epigenome is flexible

80
Q

How is the epigenome flexible?

A

Because the chemical tags respond to environmental factors

81
Q

Which factors affect the epigenome and what can they lead to?

A

Nutrition (diet)
Hormones
Can cause chemical tags to adjust the wrapping + unwrapping of DNA so could switch genes on and off

82
Q

Why is the epigenome sometimes referred to as cellular memory?

A

As it is the accumulation of signals a cell has received during its lifetime

83
Q

Describe animal research that supports the theory of epigenetics and inheritance

A

Rats = Well cared for female offspring cope better with stress and are better mothers
Therefore good maternal behaviour is passed on through the epigenome but not via egg cells

84
Q

Describe human research that supports the theory of epigenetics and inheritance

A

Fetus exposed to high levels of glucose​
Glucose levels causes epigenetic changes in the daughter
Daughter more likely to develop gestation diabetes

85
Q

How do these changes occur in epigenome?

A

Environmental signals prompt proteins to travel inside of cell = nucleus = epigenetic tags attach to DNA

86
Q

What can these changes cause?

A

Acetylation of histones

Methylation of DNA

87
Q

What is acetylation of histones?

A

Activation/inhibition of a gene

88
Q

What is methylation of DNA?

A

Attracting enzymes that can add or remove methyl groups

89
Q

What does weak DNA histone association mean?

A

DNA-histone complex is loose
DNA accessible to transcription factors
Genes can be transcribed

90
Q

What does strong DNA histone association mean?

A

DNA-histone complex is tightly packed
DNA inaccessible to transcription factors
Genes not transcribed

91
Q

What is weak/string DNA histone association caused by?

A

Acetylation of histones

Methylation of DNA

92
Q

What does acetylation mean?

A

Acetyl group added = more accessible = more transcription

93
Q

What does deacetylation mean?

A

Acetyl group removed = less accessible = less transcription

94
Q

What is acetyl donated by?

A

Acetyl coenzyme A

95
Q

What happens if acetylation is decreased (deacetylation)?

A 
Increases positive on histones
Increased attraction to phosphate groups on DNA
DNA association stronger
DNA not accessible 
No mRNA 
Gene "switched off"
96
Q

What is methylation?

A

Adding methyl group

97
Q

Where is the methyl group added in methylation?

A

Cytosine base

98
Q

What does methylation do?

A

Inhibit transcription

99
Q

How does methylation inhibit transcription?

A

Prevents transcription factor from binding

OR attracts enzymes that condense DNA-histone complex making the DNA inaccessible to transcription factor

100
Q

What type of chromatin is it when DNA is supercoiled + not accessible for transcription?

A

Heterochromatin

101
Q

What type of chromatin is it when DNA is loosely packed + accessible?

A

Euchromatin

102
Q

Why do different types of cells have segments of heterochromatin + euchromatin?

A

Control over what is transcribe + what is not

103
Q

What will some cells chromatin do?

A

Change over time between the two types

104
Q

What happens at heterochromatin histones?

A

Decreased acetylation

105
Q

What happens at euchromatin histones?

A

Increase acetylation

106
Q

What happens at heterochromatin DNA?

A

Increased methylation

107
Q

What happens at euchromatin DNA?

A

Decreased methylation

108
Q

Describe heterochromatin DNA-histone complex

A

More condensed

109
Q

Describe euchromatin DNA-histone complex

A

Less condensed

110
Q

Can heterochromatin be accessed by transcription factors?

111
Q

Can euchromatin be accessed by transcription factors?

112
Q

What type of gene is heterochromatin?

113
Q

What type of gene is euchromatin?

114
Q

In experiment one of epigenetic rats what did they want to do?

A

How upbringing effects stress in later life

115
Q

What did experiment one reveal?

A

Attentive mother pups = decreased stress = decreased methylation = genes accessible
Inattentive mother pups = increased stress

116
Q

What did experiment one also reveal?

A

It was passed on to the pups own offspring

117
Q

In experiment two what did they want to do?

A

If it was due to mother’s behaviour or her genes

118
Q

What did experiment two reveal?

A

Attentive mother foster pups = decreased stress

Inattentive mother foster pups = increased stress

119
Q

In experiment three what did they want to do?

A

To prove that epigenetic change was directly caused in behavioural changes in the adult

120
Q

What did experiment three reveal?

A

“Damaged” pups given Trichostatin A = epigenetic change disappears

121
Q

What do inattentive mothers in rodents cause?

A

Methylation of genes for oestrogen receptors in the brain

122
Q

What happens to the offspring of inattentive mothers when they grow up?

A

Decreased oestrogen receptors = makes them less attentive

123
Q

What can changes in epigenetics cause?

A

Activate or silence genes

124
Q

What do cancer cells tend to have?

A

High methylation

Causes genes that are usually switched on to be switched off

125
Q

What can changes in the epigenetics lead to?

A

Increase in mutagenetic rate

126
Q

What can some genes do?

A

Repair DNA = reduce incidence of cancer

127
Q

What can happen to genes that repair DNA?

A

Increased methylation can switch them off

Damaged DNA can be replicated = cancer

128
Q

What are examples of epigenetic therapy?

A

Use drugs to inhibit enzymes involved in histone acetylation or DNA methylation
Target cancer cells specifically

129
Q

What are the problems with epigenetic therapy?

A

Alternating healthy cells could initiate cancer

130
Q

Describe epigenetic diagnosis

A

Identify amount of DNA methylation + histone acetylation at disease onset

131
Q

What does epigenetic allow?

A

Detect diseases early onset

= early treatment

132
Q

Describe RNA interference

A

Double stranded RNA cut by enzymes
Produces siRNA
One of 2 siRNA strands combine with enzyme
siRNA strand guides enzyme to mRNA strand
Enzyme cuts mRNA = translation interrupted

133
Q

What is siRNA?

A

Small interference RNA

134
Q

What are the uses of siRNA?

A

Block certain genes = observe effects occur = reveal role of gene
Some genetic disorders caused by expression of certain genes = could be blocked = prevent disease

135
Q

What was the aim of the Human Genome Project?

A

Provide complete + accurate sequence of 3 billion DNA base pairs that make up human genome

136
Q

What is the genome?

A

Complete set of chromosomes/DNA in gametes

137
Q

What are bioinformatics?

A

The science of collecting + analysing complex biological data - using computers + algorithms

138
Q

What is the whole genome shotgun (WGS)?

A

Sequencing long sequences of DNA
Sequencing overlapping DNA fragments in parallel
Using computer to assemble small fragments into larger sequences

139
Q

What are SNPs?

A

Single nucleotide polymorphisms

140
Q

Why are SNPs useful?

A

Identify genetic difference amongst individuals

141
Q

What has gene screening allowed for?

A

Identify genes associated with disease

142
Q

What is the proteome?

A

All proteins that are or can be expressed by cell, tissue + organism

143
Q

What is the difference between proteome + cellular proteome?

A

Cellular = collection of proteins found in a particular cell under certain conditions

144
Q

What is the Human Microbiome Project?

A

Studies the genomes of microorganisms associated with health + disease

145
Q

What will Human Microbiome Project research be used for?

A

Help develop new treatments

146
Q

Why is it “easy” to determine the proteome of prokaryotes?

A

Have much less non-coding DNA

147
Q

What are the applications of prokaryotes proteome?

A

Understand disease causing bacteria

Antigens can be used in vaccines

148
Q

What are the issues with sequencing more complex organisms?

A

Not all DNA is coding
Epigenetic factors could effect transcription
Regulatory genes control which genes are expressed

A-Level Biology (21 decks)

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