IMMS revision questions Flashcards
(180 cards)
1
Q
Where is DNA found?
A
The nucleus and mitochondria
2
Q
What is the structure of a chromosome?
A
DNA wound into a double helix, coiled around histones, and supercoiled into a chromosome. Short arm (p) long arm (q)
3
Q
How many chromosomes in the human genome?
A
46 (23 pairs)
4
Q
What is the purpose of mitosis?
A
For producing daughter cells that are genetically the same as the parents, for growth and to replace dead cells
5
Q
What are the four parts to the cell cycle?
A
Mitosis, Growth phase 1, synthesis phase, Growth phase 2
6
Q
What is the collective term for G1, G2 and the synthesis phase?
A
Interphase
7
Q
What occurs during interphase?
A
DNA replication, centrosome replication
8
Q
What happens during prophase?
A
Chromatin condenses into chromosomes, centrosomes nucleate microtubules and move to opposite poles of nucleus
9
Q
What happens during prometaphase?
A
Nuclear membrane breaks down, microtubules invade nuclear space, chromatids attach to microtubules
10
Q
What happens during metaphase?
A
Chromosomes line up along equatorial plane (metaphase plate)
11
Q
What happens during anaphase?
A
Sister chromatids separate and are pushed to opposite poles of the cell
12
Q
What happens during telophase?
A
nuclear membranes reform, chromosomes unfold into chromatin, cytokinesis begins
13
Q
What can studying mitosis be useful for clinically?
A
Detecting chromosomal abnormalities, categorising tumours, grading malignant tumours
14
Q
What is meiosis?
A
The production of 4 genetically different daughter cells
15
Q
How does meiosis for sperm differ from egg cells?
A
meiotic divisions commence at puberty, cytoplasm divides equally into four identical gametes, millions of sperm are continually produced
16
Q
How does meiosis for egg cells differ from sperm?
A
oogonia enter prophase 1 by 8th month of intrauterine life, process suspended until female reaches puberty. Cytoplasm divides unevenly (1 egg and 3 polar bodies produced) meiosis 2 only completed if fertilisation occurs
17
Q
How are spermatogonia produced?
A
primordial germ cells mitose into spermatogonia
18
Q
How are oogonia produced?
A
primordial germ cells undergo mitosis 30 times into oogonia
19
Q
What is non-disjunction?
A
Failure of chromosome pairs to separate in meiosis I or sister chromatids to separate properly in meiosis II
20
Q
What is gonadal mosaicism?
A
When precursor germline cells to ova or spermatozoa are a mixture of two or more genetically different cell lines - one is normal one is mutated
21
Q
What are the three classifications of genetic disease?
A
Chromosomal, mendelian, non-traditional
22
Q
Give examples of mendelian genetic disease types
A
autosomal dominant/recessive, x-linked
23
Q
Give examples of non-traditional genetic disease types
A
mitochondrial, imprinting, mosaicism
24
Q
What are the three domains of public health?
A
Health promotion, Health protection, Improving health services
25
Give examples of health promotion
Through education, employment, housing, surveillance
26
Give examples of areas in health protection
Environmental hazards, chemicals, radiation, infectious diseases
27
What is a multifactorial condition?
A disease due to a combination of genetic and environmental factors
28
Which studies can be used to identify if a disease as a genetic component?
twin studies, family studies, adoption studies
29
How do family studies work?
You compare the incidence of a disease amongst relatives of an affected individual compared to the general population
30
What is a monozygotic twin?
an identical twin
31
What is a dizygotic twin?
a non-identical twin
32
How is heritability of a disease expressed?
as a proportion or percentage
33
What are the characteristics of multifactorial inheritance?
The incidence of the condition is greatest amongst the closest relatives of severely affected patients
34
What is GWAS?
Genome Wide Association Studies
35
What is a neural tube defect?
Defective closure of the developing neural tube during the first month of embryonic life
36
What environmental factors affect embryogenesis?
Drugs, chemicals (thalidomide, alcohol), maternal infections (rubella), radiation, diabetes
37
What is the role of cytogenetics?
confirmation of malignancy, classification of a disease type, prognosis, monitoring, looking for inherited abnormalities
38
Where is the centromere found?
At any point on a chromosome (specific to each one)
39
What is a fusion/hybrid gene?
When a break occurs between the two genes involved and fusion creates a hybrid gene
40
What are the six main types of genetic testing?
diagnostic, carrier, predictive, pre-natal test, paternal test, genetic fingerprinting
41
What are the two methods of gene sequencing?
Sanger sequencing, Next generation Sequencing (NGS)
42
What are the features of sanger sequencing?
Single start point, single DNA fragment sequenced, high cost per gene, time consuming, very accurate, simple to analyse
43
What are the features of NGS sequencing?
library of DNA fragments, low cost per gene, very fast, huge amount of raw data to interpret, moderately accurate
44
What is the problem with NGS sequencing?
Sometimes secondary findings occur - consent is really key before any genetic test
45
What are the advantages of targeted panels?
specific genes are selected to sequence, less noise, fewer variants of uncertain significance
46
What are the two categories of chromosome abnormalities?
Numerical, structural
47
Give examples of numerical chromosome abnormalities
trisomy (1 extra chromosome), monosomy (1 less chromosome), polyploidy (more than 2 paired sets of chromosomes)
48
Give examples of structural chromosome abnormalities
translocation, inversions, duplications, deletions
49
When can non-disjunction occur?
In meiosis 1 or 2
50
What is Edwards syndrome?
When a person has an extra chromosome 18
51
What is Patau syndrome?
When a person has an extra chromosome 13
52
What is Klinefelter syndrome?
When a person has XXY
53
What is triple X syndrome?
When a person has XXX
54
What is turner syndrome?
When a person has only one sex chromosome X
55
Is maternal and paternal triploidy the same?
No
56
What is reciprocal translocation?
When part of one chromosome breaks off and attaches itself to the end of another chromosome
57
What is FISH?
Fluorescence in situ hybridisation - when DNA probes are used with fluorophores
58
What is a microarray?
A new technology which improves the resolution of detection of cytogenetic abnormalities
59
What is a constitutional mutation?
Mutation that occurs at gametogenesis, affects all cells of the body, heritable
60
What is an acquired mutation?
Mutation occurs during lifetime, restricted to malignant tissue, not heritable
61
What are the four main categories of genetic disorders?
Chromosome abnormalities, single gene disorders, multifactorial, polygenic disorders
62
Give examples of common changes in the structure of a chromosome
Translocation, deletion, inversions, duplications, ring chromosomes
63
What is a terminal deletion?
When the end of a chromosome is deleted
64
What does 'de novo' mean?
'In child' - the condition is not inherited from the parents
65
What are Mendel's three laws?
Segregation - for any gene, when the alleles are made the alleles separate
Dominance - for any gene one allele will be dominant and the other recessive
Independent Assortment
66
Give examples of mendelian inheritance
Autosomal vs sex-linked, dominant vs recessive
67
Give examples of non-mendelian inheritance
Imprinting, mosaicism, mitochondrial inheritance, multifactorial
68
What does a blank square mean on a pedigree chart?
unaffected male
69
What does a coloured circle mean on a pedigree chart?
affected female
70
What does a square with a diagonal line through it mean on a pedigree chart?
deceased male
71
On a pedigree chart what is the relationship between two people if they are connected by a double line?
Reproductive unity between two relatives
72
What does a triangle mean on a pedigree chart?
miscarriage
73
What does a diamond mean on a pedigree chart?
The sex is unknown
74
What is an autosome?
Any chromosome other than a sex chromosome
75
Define homozygous
The presence of two identical alleles at a given locus
76
Define heterozygous
The presence of two different alleles at a given locus
77
What is allelic heterogeneity?
The situation where different mutations result in the same clinical condition
78
What are the characteristics of an a autosomal recessive condition?
males and females affected in equal proportions, affected individuals only in a single generation
79
What does consanguineous mean?
Reproductive unity between two relatives
80
What does autozygosity mean?
homozygosity by descent (inheritance of the same altered gene through two branches of the same family - after consanguineous relationship)
81
What are the characteristics of an autosomal dominant condition?
Males and females affected in equal proportions, affected individuals in multiple generations, transmission by individuals of both sexes to both sexes
82
What is penetrance?
The percentage of individuals with a specific genotype showing the expected phenotype
83
What is expressivity?
The range of phenotypes expressed by a specific genotype
84
What is anticipation (in genetics) ?
Where a gene disorder affects successive generations, severity of the disorder increases through the generations usually due to expansion of triplet repeat sequences
85
What is somatic mosaicism?
When a genetic fault is present only in some tissues of the body
86
What is gonadal (germline) mosaicism?
When the genetic fault is present in gonadal tissue - different variants are found within gonadal cells
87
Define 'late onset'
The condition does not manifest at birth
88
Define congenial
The condition manifests itself at birth
89
What is a sex-limited condition?
Inherited condition in AD pattern that affects on sex more than the other e.g BRCA1
90
What are the characteristics of X-linked inheritance?
usually only males affected, usually transmitted through unaffected females, no male-to-male transmission
91
What is lyonization?
X-inactivation - generally only one of two x chromosomes are active in the female cell - can be skewed if one is mutated
92
What is genomic imprinting?
An epigenetic phenomenon that causes genes to be expressed in a parent-of-origin manner
93
How is mitochondrial DNA inherited?
From mother to child
94
What is homoplasmy?
A eukaryotic cell whose copies of mitochondrial DNA are all identical
95
What is heteroplasmy?
When there are multiple copies of mtDNA in each cell with different mutations
96
What is a mitochondrial disease?
A group of genetic diseases caused by dysfunctional mitochondria
97
What is a polymorphism?
A benign allelic variant
98
What is a pathogenic variant?
A harmful allelic variant
99
What are the seven main types of variant?
Duplications, deletions, splice-site variants, variants within the regulatory sequence, nonsense variant, mis-sense variant, expansion of trinucleotide repeats
100
What is a mis-sense variant?
Where one amino acid is replaced by another
101
What is a non-sense variant?
The introduction of a premature stop codon
102
What are the two categories of deletions?
Out-of-frame / in-frame
103
What is a splice-site variant?
Where some of the splice site is deleted causing the introns to be translated
104
What is the splice acceptor site?
four bases at the start of a non-coding region indicating where the non-coding region starts
105
What is non-sense mediated decay?
A surveillance pathway that removes mRNA transcripts containing premature stop codons
106
How can you tell if it is a polymorphism or a pathogenic variant?
If it disrupts the active site or spice site, not seen in large number of normal individuals, seen in other individuals with the same condition, functional studies
107
Give three examples of conditions caused by expansion of a tri-nucleotide repeat
Huntingdon's disease, myotonic dystrophy, Fragile X syndrome
108
What is allelic heterogeneity?
When there are lots of variants of one gene
109
What is locus heterogeneity?
When variants in different genes give the same clinical conditions
110
What are the three mechanisms of dominance?
loss-of-function variants, gain-of-function variants, dominant-negative variants
111
What is a loss-of-function variant?
Where only one allele is functioning, if a pathway is very sensitive to the amount of product produced, having only one working allele will cause a problem
112
What is a gain-of-function variant?
When increases gene dosage = increased gene activity
113
What is a dominant-negative variant?
Where the protein from the variant allele interferes with the protein from the normal allele
114
What is a diagnostic test?
If a patient shows symptoms of a disease, a molecular genetic test could confirm diagnosis
115
What is a pre-natal test?
A test performed during pregnancy, usually by amniocentesis or a chromonic villous sample
116
What is pre-implantation genetic diagnosis?
Testing of one cell from a blastocyst in IVF
117
What is a living organism?
Something made up of one or more cells, capable of reproduction, that responds to the environment, grows and requires energy
118
What are macromolecules?
large, complex, heterogeneous molecules e.g. haemoglobin
119
What is an oligosaccharide?
A polysaccharide with a carbon chain length of 3-12
120
What is a chiral centre?
A carbon with four different groups attached
121
What are the names of the two optically active forms when there is a chiral centre?
L and D - most sugars in living organisms are D
122
How can monosaccharides become ring structures?
The carbonyl group reacts with the hydroxyl group on the same molecule
123
Name four sugar derivatives
aminosugars, alcohol-sugars, phosphorylated sugars, sulphated sugars
124
What is a glycosidic bond?
A bond between monosaccharides formed when a hydroxyl group reacts with a NH or OH group
125
Where are O-glycosidic bonds found?
In polysaccharides
126
Where are N-glycosidic bonds found?
In DNA and nucleotides
127
What is a proteoglycan?
A long unbranched polysaccharide radiating from a core protein e.g. cartilage
128
What is glycogen?
A storage molecule made from polysaccharides attached to glycogenin
129
What are lipids?
Molecules made from fatty acids and glycerol
130
What does this mean when naming a fatty acid?
| 18:1 (triangle)^9
18 carbons long, with one double bond which is on the ninth carbon from the methyl group
131
What are phosphoacylglycerols?
messenger molecules found in cell membranes
132
What are sphingolipids?
molecules found in cell membranes of the brain and nerves
133
What are nucleotides?
The monomers that make up DNA, they consist of a sugar, phosphate group and a nitrogenous base
134
What is a nucleoside?
The sugar and nitrogenous base part of a nucleotide
135
What are the parts of an amino acid?
central carbon, amino group, carboxyl group, hydrogen group and a variable group
136
How does an amino acid's structure change with pH?
Hydrogen ions are removed from the carboxyl group or added to the amino group
137
Give some examples of types of proteins
immunoglobulins, fibrous proteins, enzymes, carrier proteins, receptors, neurotransmitters
138
What is a polypeptide?
A long chain of amino acids
139
What are the properties of peptide bonds?
They are very stable (only cleaved by proteolytic enzymes), flexible so allow multiple conformations
140
Which forces hold proteins together?
Van der Waals forces, hydrogen bonds, hydrophobic forces, ionic bonds and disulphide bonds
141
What are van der waals forces?
weak forces of interaction between atoms due to fluctuating electrical charges
142
What are hydrogen bonds?
Strong intermolecular forces between hydrogen atoms and the lone pair of electrons on a N, O, or F atom
143
What are hydrophobic forces?
non-polar side chains are repelled by water so they tend to form tightly packed cores at the centre of a protein
144
What is primary structure?
The sequence of amino acids in the chain
145
What is secondary structure?
the simple folding of amino acid chains into alpha helixes or beta-pleated sheets
146
What are the supersecondary structures?
helix-turn-helix, leucine zipper, beta-alpha-beta unit, zinc finger
147
What is tertiary structure?
When secondary structures fold round themselves to form complex 3D molecules
148
What is quaternary structure?
a complex 3D structure comprising of more than one polypeptide chain
149
What factors influence the rate of a reaction?
temperature, concentration, pressure, catalysts, surface area of reactant, pressure
150
What are isoenzymes?
enzymes with a difference sequence and structure but catalyse the same reactions
151
What are coenzymes?
structures which aid the function of enzymes
152
What do activation-transfer coenzymes do?
they form a covalent bond and are regenerated at the end of the reaction
153
What do oxidation-reduction coenzymes do?
They are involved in reactions where electrons are transferred from one compound to another
154
What is the structure of haemoglobin?
four polypeptide chains - two alpha and two beta. at the centre of the heme molecule is aporphyrin ring containing an iron ion
155
What factors affect the structure of haemoglobin?
temperature, O2 partial pressure, CO2 partial pressure, pH
156
What is sickle cell anaemia?
a genetic disorder characterised by the formation of hard sickle-shaped red blood cells, it is caused by a mutation in haemoglobin
157
What are immunoglobulins?
Antibodies
158
What is the structure of an antibody?
They are made from two heavy chains and two light chains, disulphide bonds hold the chains together
159
What is DNA like in prokaryotes?
no nuclear membrane, DNA is often arranged in a single chromosome
160
What is DNA like in eukaryotes?
DNA found in the nucleus, bound to proteins, normally in the form of chromosomes, some DNA in mitochondria
161
What are the functions of DNA?
Acts as a template and regulator for transcription and protein synthesis, structural basis of heredity and genetic diseases
162
What are the pyramidine bases?
Cytosine, Thymine, Uracil
163
What are the purine bases?
Adenine, Guanine
164
What are the useful properties of DNA?
Heat denaturation, alkali dissociation, hybridisation
165
what is the structure of a prokaryotic chromosome?
supercoiled, circular chromosomes, 2mm linear
166
What is the structure of a eukaryotic chromosome?
complex packaging, with histones, 2m long
167
Explain the basic concept of DNA replication
DNA opens at the replication fork, the base sequence on each parent strand is copied onto a complementary daughter strand, two new strands separated in front of the fork, new DNA is made behind the fork
168
Explain DNA replication in prokaryotes?
A binding protein starts the process at a single point of origin, the parental strands separate and form a bubble, both strands are copied simultanteously and in opposite directions, sequences are proof read, replication ends at the termination point, DNA is circularised by ligases, cytokinesis occurs
169
Which enzymes are involved in DNA replication?
Polymerases, ligases, helicases, nuclease, primase, topoisomerase
170
Which way does DNA polymerase read and print?
It reads 3' to 5'
| It prints 5' to 3'
171
What are the substrates to DNA polymerase?
deoxyribonucleotides and triphosphates
172
Which enzymes open up the DNA strand?
Helicase opens the strand, Ssb proteins keep it open, tropoisomerase unwinds it
173
How does DNA replication occur with the lagging strand?
DNA polymerase is complementary to the leading strand not the lagging strand so small RNA chains (okazaki fragments) complementary base pair onto the lagging strand, a repair DNA polymerase enzyme, fills in the gaps between fragments and ligase joins the fragments together
174
What are the ways DNA is repaired?
base or nucleotide excision, mismatch repair, transcription-coupled repair
175
What is the process of PCR?
Heat to 94 degrees to separate strands, cool to add primers, add heat-stable DNA polymerase - repeat, each cycle the amount of strands doubles
176
What are the three types of RNA?
mRNA, rRNA, tRNA
177
What is mRNA?
A long linear molecule with a poly-A-tail (group of adenine nucleotides at the end)
178
What are 80s ribosomes made from?
The four main types of rRNA and proteins
179
What does tRNA do?
It carries amino acids to ribosomes
180
What is the structure of a tRNA molecule?
Cloverleaf shape, RNA folded and held together by disulphide bridges, has an amino acid binding site, an anticodon
