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
2
Q
What are the two types of mutations?
A
Gene mutation
Chromosome mutation
3
Q
What is polyploidy?
A
3 or more sets of chromosomes
4
Q
What is non-disjunction?
A
When homologous pairs fail to separate during meiosis
5
Q
What is substitution?
A
Nucleotide base is replaced with a different nucleotide with a different base
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
7
Q
What does it mean if a stop codon is formed in substitution?
A
Polypeptide formation stopped prematurely
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
9
Q
What does it mean if a different codon is produced but codes for same amino acid in substitution?
A
Degenerate
No effect
10
Q
What is deletion?
A
Nucleotide base has been removed from the sequence
11
Q
What will deletion cause?
A
Frame shift (left) So all amino acids are different
12
Q
How can the effect of deletion be made worse?
A
If deleted base is at beginning of sequence
13
Q
What is the effect of adding a base?
A
Frameshift (right)
14
Q
What happens if three bases are added to the sequence?
A
= no effect as no frameshift
15
Q
What is the effect of duplicating a base?
A
Frameshift
16
Q
What is inversion?
A
A group of bases separate from the sequence + re-join sequence in some place BUT in inverse order
17
Q
What is translocation?
A
Group of bases separate from one chromosome + joins the other
18
Q
What does translocation between chromosome 9 and 22 cause?
A
Leukaemia
19
Q
What does translocation cause?
A
Marked effect
20
Q
Is translocation a mutation?
A
YES
21
Q
Is crossing over a mutation?
A
NO
22
Q
Why is translocation a mutation?
A
Change in genetic information between non-homologous chromosomes
23
Q
Why isn’t crossing over a mutation?
A
Swaps genetic material BUT homologous chromosomes unchanged
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
25
What can mutagenetic reagents cause?
Natural mutation rate to increase
26
What are some mutagenetic reagents?
Chemicals - NO2 + benzopyrene
| High energy ionising radiation - Alpha, beta, X-rays + UV
27
What does NO2 + benzopyrene do?
```
NO2 = affect transcription
Benzopyrene = inactivates tumour suppressor gene
```
28
What is differentiation?
The process by which cells develop special structures needed to carry out specific role
29
What do multicellular organisms require?
Specialised cells to carry out specific functions
30
What are stem cells?
Undifferentiated cells that can divide into any cell
31
What is self-renewal?
The ability to go through numerous cycles of cell division while maintaining the undifferentiated state
32
Where do you find stem cells?
Embryonic - flexible
Adult tissues - non-flexible
Specific to tissue/organ ^^^
33
What are totipotent stem cells?
Can produce all cell types (embryo + placenta)
| Only present during 1st few cell divisions
34
What are pluripotent stem cells?
Can become any body cell in embryo
| BUT not placenta
35
Why are pluripotent used in medicine?
Can divide in unlimited numbers
36
What are multipotent stem cells?
Found in adults
Give rise to different types of specialised cells
BUT restricted to certain organs/tissue types
37
What are unipotent stem cells?
Found in adults
| Make only one type of cell
38
Why are embryonic cells important?
Differentiate into any type of cell
39
What males a cell become specialised?
Different gene expressed
| So only some DNA translated to proteins
40
Do all body cells make all the products they are genetically capable of?
No = waste resources unfavourable
41
How is gene expression controlled?
Some permanently expressed
Some never expressed
Some switch on + off
42
How are genes prevented from expressing themselves?
Prevent transcription
| Breakdown of mRNA before translation
43
What are cardiomyocytes?
heart muscle cells
| That can be replaced by unipotent stem cells when damaged
44
What is myocardial infraction?
Heart attack when coronary arteries are blocked
45
What impact does myocardial infraction have?
No blood flow = cells die
46
How do cardiomyocytes help with myocardial infraction?
Inject into damaged area = regenerate them when differentiate
47
How are embryonic stem cells used?
Cells taken from early stages of embryo
Grown in vitro
Induced to develop into tissues
48
What can embryonic stem cells be used for?
```
Burns
Parkinson's disease
Nerve damage
Diabetes
Heart disease
Cancer
```
49
What are iPS cells?
Type of induced pluripotent cell that is produced from unipotent cells
50
How are iPS cells created?
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
51
What does iPS cells show since they can be reactivated?
They retain the same info present in the embryo
52
What is interesting about iPS cells?
Capable of self-renewal
Very flexible
Potentially divide to provide limitless supply
53
How could iPS cells be useful?
Could replace embryonic stem cells in medicine + research
| = overcome ethical issues
54
Do plants have stem cells?
YES
| Mature plants have totipotent stem cells = them to form clones of single cells
55
What are the arguments for stem cells?
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
56
What are the arguments against stem cells?
```
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
```
57
What are the basics of gene expression?
Transcription has to occur
pre-mRNA spliced
Translation has to occur
58
What do protein hormones do?
Help in gene expression
| Act via 2nd messenger
59
What do lipid-soluble hormones do?
Act directly
| Regulate transcription + translation
60
What is an example of a lipid-soluble hormone?
Oestrogen
61
What must happen for transcription to happen?
Genes be "switched on"
62
What are transcription factors?
Regulatory proteins that control what is "switched on"
63
Where do transcription factors move?
Cytoplasm ----> nucleus
64
What does a transcription factor have?
DNA binding site
65
What is a transcription factor attached to?
Receptor with hormone binding site
66
What is the DNA binding site specific to?
To the gene
67
What happens when the transcription factor binds to the correct region of DNA?
Transcription begins = produced mRNA
68
What happens if the gen is not expressed?
DNA binding site blocked = transcription stopped
69
What happens with the lipid-soluble hormone?
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
How did Darwin and Lamarck's theory differ?
```
Lamarck = environmental factors then passed to offspring
Darwin = natural selection
```
71
What is epigenetics?
How environmental influences can alter genetic inheritance
72
Which environmental factors are thought to influence the genetic inheritance of an organisms offspring?
Diet
Stress
Toxins
73
What are the possible uses of studying epigenetics?
Therapeutic
Provide cures
Understand genetics behind cancer
74
What are histones?
Protein molecules that are rich in chemicals + bind tightly to negatively-charged phosphates in DNA
75
What do histones help to form?
Chromosomes
76
What is the epigenome?
Layer of chemical tags that cover histones
77
What does the epigenome determine?
Shape of DNA-histone complex
78
How does the epigenome determine the shape of the DNA-histone complex?
By keeping genes that are inactive in a tight arrangement so they cannot be read
79
What is the difference between DNA code and the epigenome?
DNA is fixed whereas the epigenome is flexible
80
How is the epigenome flexible?
Because the chemical tags respond to environmental factors
81
Which factors affect the epigenome and what can they lead to?
Nutrition (diet)
Hormones
Can cause chemical tags to adjust the wrapping + unwrapping of DNA so could switch genes on and off
82
Why is the epigenome sometimes referred to as cellular memory?
As it is the accumulation of signals a cell has received during its lifetime
83
Describe animal research that supports the theory of epigenetics and inheritance
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
Describe human research that supports the theory of epigenetics and inheritance
Fetus exposed to high levels of glucose
Glucose levels causes epigenetic changes in the daughter
Daughter more likely to develop gestation diabetes
85
How do these changes occur in epigenome?
Environmental signals prompt proteins to travel inside of cell = nucleus = epigenetic tags attach to DNA
86
What can these changes cause?
Acetylation of histones
| Methylation of DNA
87
What is acetylation of histones?
Activation/inhibition of a gene
88
What is methylation of DNA?
Attracting enzymes that can add or remove methyl groups
89
What does weak DNA histone association mean?
DNA-histone complex is loose
DNA accessible to transcription factors
Genes can be transcribed
90
What does strong DNA histone association mean?
DNA-histone complex is tightly packed
DNA inaccessible to transcription factors
Genes not transcribed
91
What is weak/string DNA histone association caused by?
Acetylation of histones
| Methylation of DNA
92
What does acetylation mean?
Acetyl group added = more accessible = more transcription
93
What does deacetylation mean?
Acetyl group removed = less accessible = less transcription
94
What is acetyl donated by?
Acetyl coenzyme A
95
What happens if acetylation is decreased (deacetylation)?
```
Increases positive on histones
Increased attraction to phosphate groups on DNA
DNA association stronger
DNA not accessible
No mRNA
Gene "switched off"
```
96
What is methylation?
Adding methyl group
97
Where is the methyl group added in methylation?
Cytosine base
98
What does methylation do?
Inhibit transcription
99
How does methylation inhibit transcription?
Prevents transcription factor from binding
| OR attracts enzymes that condense DNA-histone complex making the DNA inaccessible to transcription factor
100
What type of chromatin is it when DNA is supercoiled + not accessible for transcription?
Heterochromatin
101
What type of chromatin is it when DNA is loosely packed + accessible?
Euchromatin
102
Why do different types of cells have segments of heterochromatin + euchromatin?
Control over what is transcribe + what is not
103
What will some cells chromatin do?
Change over time between the two types
104
What happens at heterochromatin histones?
Decreased acetylation
105
What happens at euchromatin histones?
Increase acetylation
106
What happens at heterochromatin DNA?
Increased methylation
107
What happens at euchromatin DNA?
Decreased methylation
108
Describe heterochromatin DNA-histone complex
More condensed
109
Describe euchromatin DNA-histone complex
Less condensed
110
Can heterochromatin be accessed by transcription factors?
NO
111
Can euchromatin be accessed by transcription factors?
YES
112
What type of gene is heterochromatin?
Inactive
113
What type of gene is euchromatin?
Active
114
In experiment one of epigenetic rats what did they want to do?
How upbringing effects stress in later life
115
What did experiment one reveal?
Attentive mother pups = decreased stress = decreased methylation = genes accessible
Inattentive mother pups = increased stress
116
What did experiment one also reveal?
It was passed on to the pups own offspring
117
In experiment two what did they want to do?
If it was due to mother's behaviour or her genes
118
What did experiment two reveal?
Attentive mother foster pups = decreased stress
| Inattentive mother foster pups = increased stress
119
In experiment three what did they want to do?
To prove that epigenetic change was directly caused in behavioural changes in the adult
120
What did experiment three reveal?
"Damaged" pups given Trichostatin A = epigenetic change disappears
121
What do inattentive mothers in rodents cause?
Methylation of genes for oestrogen receptors in the brain
122
What happens to the offspring of inattentive mothers when they grow up?
Decreased oestrogen receptors = makes them less attentive
123
What can changes in epigenetics cause?
Activate or silence genes
124
What do cancer cells tend to have?
High methylation
| Causes genes that are usually switched on to be switched off
125
What can changes in the epigenetics lead to?
Increase in mutagenetic rate
126
What can some genes do?
Repair DNA = reduce incidence of cancer
127
What can happen to genes that repair DNA?
Increased methylation can switch them off
| Damaged DNA can be replicated = cancer
128
What are examples of epigenetic therapy?
Use drugs to inhibit enzymes involved in histone acetylation or DNA methylation
Target cancer cells specifically
129
What are the problems with epigenetic therapy?
Alternating healthy cells could initiate cancer
130
Describe epigenetic diagnosis
Identify amount of DNA methylation + histone acetylation at disease onset
131
What does epigenetic allow?
Detect diseases early onset
| = early treatment
132
Describe RNA interference
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
What is siRNA?
Small interference RNA
134
What are the uses of siRNA?
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
What was the aim of the Human Genome Project?
Provide complete + accurate sequence of 3 billion DNA base pairs that make up human genome
136
What is the genome?
Complete set of chromosomes/DNA in gametes
137
What are bioinformatics?
The science of collecting + analysing complex biological data - using computers + algorithms
138
What is the whole genome shotgun (WGS)?
Sequencing long sequences of DNA
Sequencing overlapping DNA fragments in parallel
Using computer to assemble small fragments into larger sequences
139
What are SNPs?
Single nucleotide polymorphisms
140
Why are SNPs useful?
Identify genetic difference amongst individuals
141
What has gene screening allowed for?
Identify genes associated with disease
142
What is the proteome?
All proteins that are or can be expressed by cell, tissue + organism
143
What is the difference between proteome + cellular proteome?
Cellular = collection of proteins found in a particular cell under certain conditions
144
What is the Human Microbiome Project?
Studies the genomes of microorganisms associated with health + disease
145
What will Human Microbiome Project research be used for?
Help develop new treatments
146
Why is it "easy" to determine the proteome of prokaryotes?
Have much less non-coding DNA
147
What are the applications of prokaryotes proteome?
Understand disease causing bacteria
| Antigens can be used in vaccines
148
What are the issues with sequencing more complex organisms?
Not all DNA is coding
Epigenetic factors could effect transcription
Regulatory genes control which genes are expressed
