principles genetics Flashcards
1
Q
what is a missense mutation
A
change of amino acid sequence
2
Q
what is a nonsense mutation
A
new termination code
3
Q
what is a silent mutation
A
no change of the amino acid sequence
4
Q
what is a frameshift mutation
A
addition or deletion of a base
5
Q
what kind of mutation is sickle cell anaemia
A
missense
6
Q
what type of inheritance is sickle cell anaemia
A
co-dominant
7
Q
what is klienfelters syndrome
A
3 sex chromosomes (47 XXY)
8
Q
what is haemophilia A a genetic deficiency of
A
clotting factor VIII
9
Q
what kind of inheritance is haemophilia A
A
X linked recessive but can be spontaneous mutation
10
Q
are histones positively or negatively charged
A
positive
11
Q
what is the DNA cycle
A
G1 - S - G2 - M - G1
12
Q
what does mitosis produce
A
2 identical diploid daughter cells
13
Q
what does meiosis produce
A
4 nonidentical haploid daughter cells
14
Q
where does variation in meiosis come from
A
crossing over
independent assortment of homologous chromosomes
15
Q
what occurs in G1
A
cell growth
16
Q
when can mutation occur in the cell cycle
A
between G2 + M and GI + S
17
Q
what / when is G0
A
between G1 and S
when cell functions normally and doesn’t replicate - most of life
18
Q
when does DNA synthesis and replication occur
A
S phase
S for synthesis
19
Q
what occurs during G2
A
DNA replication checked
2nd growth phase - involving proteins etc
20
Q
what occurs during M
A
mitosis
m for mitosis
21
Q
what can you see with Karyotyping
A
deletions of >5 million base pairings
looks at chromosomes as a whole
22
Q
what is transcription
A
DNA to RNA
23
Q
what is translation
A
RNA to protein
24
Q
what are SNPs
A
single nucleotide polymorphisms
sequence changes in DNA between genes
25
what is a polymorphism
any variation in a human genome which has a population frequency of >1%
doesn't cause disease in its own right but may predispose to a common disease
26
what is a mutation
DNA variant that causes or predisposes to a specific disease
| any inheritable change in the human genome
27
what is a multifactorial disease
multiple polymorphisms cause a risk of disease - combine with environmental factors to cause disease
genes involved will have low penetrance
28
what is balanced chromosome rearrangement
translocation - usually normal
| same amount of genetic information swapped - all chromosomal material is present
29
what is unbalanced chromosome rearrangement
translocation
extra or missing chromosomal material
usually 1 or 3 copies of some of the genome
30
what happens to the child if a parent has balanced chromosome arrangement
child inherits normal 2 copies + balanced = 3 copies
31
what is an acrocentric chromosome
centromere located very near the end of the chromosome
32
what is a telocentric chromosome
centromere located at terminal end of chromosome
33
what is epigenic variation
functional modifications to the genome that don't involve a change in nucleotide sequence
34
what is aneuploidy
whole extra or missing chromosome
35
what is translocation
rearrangement of chromosomes
36
what is reciprocal translocation
segments from 2 different chromosomes have been exchanged
37
what is monosomy
missing chromosome from a pair
38
what is trisomy
extra chromosome in a pair
39
what is down syndrome
trisomy 21
47 XY
3 copies of 21
40
what can trisomy 14 cause
miscarriage
41
what is edward syndrome
trisomy 18
42
what is turner syndrome
one sex chromosome
| 45 X
43
what is robertsonian translocation
2 accrocentric chromosomes attach at centromere
| only occurs with 13 14 15 21 22
44
what is the most sensitive technique for looking for chromosomal imbalance (absent or duplicated material)
microarray CGH
can also find polymorphisms
if patient has extra DNA - predominantly red
45
what is the best technique for looking for point mutations
PCR
46
what is the best technique for looking at lots of genes
Next generation sequencing
47
what is the best method for detection of plasma viral load in HIV patient
PCR
48
what is the best method for measurement of T lymphocytes in blood
immunophenotyping
49
what is the term to describe the presence of 2+ populations of cells with different phenotypes in one individual
mosaicism
50
what is gonadal mosaicism
2 populations of cells in gonads one with a DNA mutation or chromosome anomaly
51
what is somatic mosaicism
it is within the body cells so not passed on to children
| post-zygotic mutation
52
what genes stop cells dividing when switched on
tumour suppressors
53
what genes start cells dividing when switched on
oncogenes
54
what is cancer
mutations in a cell cause damage to control genes that allow cell to divide in uncontrolled fashion
normally atleast 3 different groups of cell with different phenotypes
55
what is penetrance
the likelihood of having a disease if you have a gene mutation
56
what is the term to describe variation in disease severity if you have the mutation
expression
57
what are the mutations in CF
CFTR mutation
- F508 deletion
- G551D mutation
58
what is the carrier frequency of CF
1/24 / 1/25
59
what is the function of the CFTR gene
channel across membranes that produce mucus, sweat, saliva, tears, digestive enzymes
transports chloride ions out of the cell which indirectly controls the water movement allowing for thin free flowing mucus
60
what happens when there are mutations in the CFTR gene
sodium is not pumped out into lumen/digestive/respiratory passages so mucus is think as water doesn't enter areas
61
what do mutations in the promoter and splice sequences cause
stop transcription or cause abnormal splicing
62
what do base changing mutations cause
change in amino acid sequence
change in protein sequence
may / may not reduce protein function
63
what is a mendelian disorder
a disease that is caused by a change in a single gene
64
what diseases are considered mendelian
```
autosomal dominant
autosomal recessive
X links
X inactivation
mitochondrial
```
65
where is the disease seen in autosomal dominant
disease seen in all generations
66
what is the risk of having an affected child in autosomal dominant
50%
67
where is the disease seen in autosomal recessive
only one generation affected
68
```
if both parents are carriers of an AR disease what is the chance a child will be
unaffected
not carriers and unaffected
affected
carrier
```
unaffected - 3/4
unaffected and not carriers - 1/4
carrier - 1/2
affected - 1/4
69
what do AR diseases usually cause
loss of function
70
are X linked diseases recessive or dominant
recessive
71
if a mother is a carrier of an XL disease what are the chances the daughter will also be a carrier
50%
72
if a mother is a carrier of an XL disease what are the chances her son will be affected
50%
73
what is X-inactivation
a cell only requires one working copy of the X chromosome so in females each cell has a random X chromosome inactivated
74
a woman who is a carrier of a X linked haemophilia experiences haemorrhage following surgery
what is the most likely mechanism
normal X inactivation
| 50% of cells will have had normal X deleted so reduced capacity for blood clotting
75
```
the following s/s are s/s of what
myopathy
diabetes
deafness
optic atrophy
stroke like episodes
encephalitis
```
mitochondrial disease
76
mitochondrial diseases are inherited almost exclusively maternally
true/false
true
77
what is the term for the mutation where there is only one working copy which is not enough
haploinsufficiency
78
what is the term for the mutation where an abnormal protein interferes with normal protein
dominant negative
79
what is the term for the mutation where it activates a gene
gain of function mutation
80
what happens when a polymorphism occurs in the promotor regions
less protein
81
mendelian disorders have a high penetrance
| true/false
true
82
what does DNA methylation lead to
modification of histones which strengthens binding and so represses transcription
83
what are 3 examples of non-mendelian inheritance
imprinting
angelman syndrome
heteroplasmy
84
what is imprinting
differences in gene expression depending on whether a gene is maternally or paternally inherited
85
what causes angel man syndrome
chromosome 15 fault
| mother's UBE3A works but fathers is methylated
86
how does angel man syndrome express itself in the phenotype
```
neuro-genetic disorder
developmental delay
intellectual disability
ataxia
epilepsy
happy demeanour
frequent laughing and smiling
```
87
what is heteroplasmy
different daughter cells contain different proportions of mutant mitochondria
88
what are 5 characteristics gained by cells on progression to cancer
```
Evasion of immune response
Acquire a vascular supply
Metastasis
Avoid apoptosis
Proliferation
```
89
what is Li Fraumeni syndrome
mutation in p53 gene resulting in defective p53 protein
90
what stage of the cell cycle may p53 halt in low O2
G2
91
give 3 mechanisms of gene activation
duplication of the gene
activation of the gene promoter
change in amino acid sequence
92
what does FISH stand for and what is it used for
Fluorescence in situ hybridisation
can light up a specific bit of chromosome if you know what bit to look for
can help identify aneuploidy or translocations etc
93
mutations in BRCA1/2 gene cause a small proportion of what cancers
familial breast/ovarian cancer
94
what is the BRCA1/2 gene involved in
DNA strand repair
95
Philadelphia chromosome can cause leukaemia. what does it involve?
9 to 22 translocation
96
the central dogma involves transcription, splicing, translation and post transcriptional modification
true/false
true
97
A female patient is short and has mild learning difficulties. She has a lack of monthly periods and is infertile. What condition is most likely?
45X
98
what is a metacentric chromosome
both arms of the chromosome are the same length
99
what is the correct symbol for the short arm of a chromosome
p
100
what disease best fits this phenotype
| A female with normal intelligence and infertility
Turner's syndrome
| An individual with the normal number of autosomes, but only one X chromosome
101
An individual with a balanced translocation between chromosomes 2 and 7, and two X chromosomes
what would the phenotype be
normal female
102
what is progeria
a rare genetic condition causing growth retardation in infancy with macrocephaly and fast developing signs of old age caused by a spontaneous mutation
