MGD Flashcards
0
Q
Functions of cytoplasm
A
Metabolism of carbohydrates, amino acids and nucleotides
Fatty acid synthesis
1
Q
Functions of Golgi body
A
Export of proteins
Detoxification reactions
2
Q
Functions of lysosomes
A
Cellular digestion
3
Q
Functions of mitochondria
A
ATP synthesis
4
Q
Functions of endoplasmic reticulum
A
Export of proteins
Membrane synthesis
Lipid and steroid synthesis
Detoxification reactions
5
Q
Functions of nucleus
A
DNA synthesis and repair
6
Q
Functions of nucleolus
A
RNA processing and ribosome assembly
7
Q
Functions of plasma membrane
A
Cell morphology and movement
Transport of ions and small molecules
8
Q
Functions of ribosomes
A
Protein synthesis
free in cytoplasm or RER
9
Q
Key differences between
prokaryotic and eukaryotic cells
A
Organism (E-PAF) (P-B)
Chromosomes (many vs one circular strand of DNA/RNA)
Ribosomes larger in E
Cytoskeleton in E vs flagella only in P
P- cell wall
E - nucleus, ER, lysosomes, Golgi complex, mitochondria, vacuoles (small/ none in animals)
OCCCRNELGMV
10
Q
Name organisms with mammalian eukaryotic cells
A
Plants
Animals
Fungi
11
Q
Name organisms with prokaryotic cells
A
Bacteria
12
Q
Do eukaryotic cells have a cell wall?
A
No
13
Q
Do eukaryotic cells have a nucleus?
A
Yes
14
Q
Do eukaryotic cells have chromosomes?
A
Many (23 pairs in humans)
15
Q
Do eukaryotic cells have an endoplasmic reticulum?
A
Yes
16
Q
Do eukaryotic cells have ribosomes?
A
Yes (large)
17
Q
Do eukaryotic cells have lysosome?
A
Yes
18
Q
Do eukaryotic cells have a Golgi complex?
A
Yes
19
Q
Do eukaryotic cells have vacuoles?
A
Ys (small/ none in animals)
20
Q
Do eukaryotic cells have mitochondria?
A
Yes
21
Q
Do eukaryotic cells have a cytoskeleton ?
A
Yes
22
Q
Do prokaryotic cells have a cell wall?
A
Yes
23
Q
Do prokaryotic cells have a nucleus?
A
No
24
Do prokaryotic cells have chromosomes?
One circular strand of DNA/RNA
25
Do prokaryotic cells have an endoplasmic reticulum?
No
26
Do prokaryotic cells have ribosomes?
No
27
Do prokaryotic cells have lysosomes?
No
28
Do prokaryotic cells have a Golgi complex?
No
29
Do prokaryotic cells have vacuoles?
No
30
Do prokaryotic cells have mitochondria?
No
31
Do prokaryotic cells have a cytoskeleton?
Flagella only
32
Describe macromolecular structure
Monomeric units
| Joined by covalent bonds
33
Describe macromolecular interaction
Non-covalent interactions
34
Types of non-covalent (weak) interactions in macromolecules
Hydrogen bonds
Ionic interactions
Hydrophobic interactions
Van der waals interactions
35
What are ionic interactions ?
Can be attraction or repulsion of charged ions
36
What are hydrophobic interactions?
| What is a hydrophobic molecule?
Non polar molecules
Unable to interact with water
E.g. Lipids
Storage without water and can pass through bilayer
37
What are van der waals interactions ?
Any two atoms in close proximity
38
What are hydrophilic molecules?
Polar molecule
Interact with water
Reduces storage ability (e.g. Glycogen)
Cannot pass through bilayer unassisted
39
What is pH?
Measurement of conc of H+ ions in a sol
Strong acids and bases completely dissociate in sol
Weak acids and bases barely dissociate
40
What is pK?
Stronger the tendency of an acid to dissociate
| the lower the pKa value
41
What are buffers?
Weak acid + conjugate base
| Resist changes in pH
42
If pH> pK
Deprotonated form dominates
43
If pH
Protonated form dominates
44
If pH =pK
Amount of acid and conjugate base is equal
45
If deprotonated form dominates
pH>pK
46
Protonated form dominates
pH
47
Amounts of acid and conjugate base are equal
pH=pK
48
Amino acid with benzene rings
Aromatic
49
Amino acid without benzene rings
Aliphatic
50
What is a zwitterion?
Neutral molecule
| Has both positive and negative charge
51
What is pI?
Isoelectric point
| pH at which the protein has no overall net charge
52
What is the pI of acidic protein?
Low pH
Many neg charged aa
Low pI
Many pos H+ ions needed to become neutral
53
What is the pI of basic protein?
High pH
Many pos charged aa
High pI
Few pos H+ ions needed to become neutral
54
Key features of peptide bond
All atoms of the bond are in the same plane
No rotation about peptide bind due to double bond characteristics
Carbonyl oxygen and amide hydrogen in trans orientation
55
Define alpha helix
Type of regular protein secondary structure
Right handed helix
3.6 aa residues per turn
Pitch of 0.54 nm
56
Define amino acid
Building blocks of proteins
Composed of central carbon attached to 4 other chemical groups:
Amino group (-NH2), carboxyl group (-COOH), hydrogen atom and variable group (R)
57
Define amphipathic
Molecule that has both a polar (hydrophilic) and non-polar (hydrophobic) end
58
Define beta sheet
Type of regular secondary structure
Polypeptide chains are on extended conformation
Parallel or anti parallel
59
Define denaturation
Disrupting the normal folded conformation of a protein to produce an unfolded polypeptide chain
60
Define domain
Region of a protein that folds into a distinct globular unit
Will often have a specific functional role within the protein
E.g. Ligand binding, interaction with other proteins
61
Define disulphide bond
Covalent bond
formed between two sulphur atoms
of cysteine residues in a protein
62
Define fibrous protein
```
Insoluble class of proteins
Elongated structure
Repeating elements
```
63
Define globular protein
```
Water soluble class of proteins
Compact highly folded structure
```
64
Define hydrogen bond
Weak electrostatic interaction
| between a hydrogen atom bound to an electronegative atom (N,O) and another electronegative atom
65
What is a protein?
Polymer composed of aa monomers joined by peptide bonds
66
How many different types of aa are there?
20
67
In which aa is the carbon not a chiral centre?
Glycine
| Variable group of hydrogen
68
Two types of spatial arrangements of aa
Chiral centre - shows stereoisomerism
| D- and L- form
69
Naturally found spatial arrangement in proteins
L-form
70
Aromatic R groups
Phenylalanine
Tyrosine
Tryptophan
PTT
71
Polar, uncharged R groups
```
Cysteine
Asparagine
Threonine
Serine
CATS
```
72
Non polar, aliphatic R groups
Glycine, alanine, methionine, proline
Lucine, isoleucine, valine
GAMPLIV
73
Negatively charged R groups
Glutamate
Aspartate
GA
74
Positively charged R groups
Histidine
Arginine
Losing
HAL
75
Define peptide bond
Type of covalent bond
Joins amino acids in proteins
Forms between carboxyl group of one and amino group of 2nd
Peptide bond formation is a condensation reaction (release H2O)
76
Define primary structure
Linear amino acid sequence of polypeptide chain
| Determines the overall structure and function of protein
77
Define secondary structure
Local spatial arrangement of polypeptide backbone
78
Define tertiary structure
Overall 3-dimensional arrangement of all atoms in a polypeptide
Involves folding secondary structure
So far apart aa on primary sequence can interact
Larger proteins have distinct domains- serve particular roles
79
Define quarternary structure
3-dimensional arrangement of multi-subunit proteins
80
Bonds in primary structure
Covalent (peptide) bonds
81
Common secondary structures of polypeptides
Alpha helix
| Beta sheet
82
Bonds involved in secondary structure
Hydrogen bonds
83
Bonds involved in tertiary structure
```
Hydrogen bonds
Van der waals
Hydrophobic interactions
Covalent disulphide bonds
Ionic interactions
```
84
Bonds involved in quaternary structure
```
Hydrogen bonds
Van der waals
Hydrophobic interactions
Covalent disulphide bonds
Ionic interactions
```
85
What is a homomeric protein?
Protein where quaternary structure consists of identical polypeptide chain subunits
86
What is a heteromeric protein?
Protein where polypeptide subunits in quaternary structure are different
87
Role of globular proteins
Enzymes
| Regulatory proteins
88
Role of fibrous proteins
Structure
Support
Protection
89
What can assist some proteins with folding?
Molecular chaperones
90
What are molecular chaperones?
Assist some proteins with folding
91
Define allosterism
The binding of a ligand/ substrate
At one site in a multi subunit protein that influences the subsequent binding of other ligand/substrates to other subunits
92
Define competitive inhibition
```
Enzyme inhibition
Inhibitor competes with substrate
For binding at the active site
Increase in the Km for the substrate
Vmax remains unchanged
```
93
Define Bohr effect
Decrease in oxygen binding affinity of haemoglobin
| caused by decrease in pH
94
Define enzyme
Biological catalyst
Increases rate of reaction
Lowering the activation energy
95
Define haem
Poryphyrin derivative
Found in haemoglobin and myoglobin
Central iron atom
Site of reversible oxygen binding
96
Define Km
Substrate concentration that will give
Half the maximal rate (Vmax)
Michaelis constant
97
Define non-competitive inhibition
Enzyme inhibition
Inhibitor binds at a site other than the active site
Decreased vmax
Km for substrate remains the same
98
Define sickle cell anaemia
Haemoglobinopathy
Glu-to-Val mutation in B-haemoglobin molecules
resulting in deformed red blood cells
99
Define thalassaemia
Group of haemoglobinopathies
caused by mutations in globin genes
resulting in an imbalance between the globin proteins
100
Define Vmax
Maximal velocity of an enzyme catalysed reaction
101
Role of myoglobin and haemoglobin
Oxygen transporting proteins
102
Name two oxygen transporting proteins
Myoglobin (Mb)
| Haemoglobin (Hb)
103
What part of haemoglobin do oxygen atoms bind to?
Haem group
104
How many oxygen molecules can myoglobin carry?
One
| Single subunit protein
105
How many oxygen molecules can Hb bind to?
Four
| Tetrameric molecule
106
Describe oxygen binding curve for Mb
Hyperbolic oxygen binding curve
| No cooperativity
107
Describe the oxygen binding curve for Hb
Sigmoidal oxygen binding kinetics
| Cooperativitiy
108
What does 2,3-BPG stand for?
2,3-bisphosphoglycerate
109
How does 2,3-BPG affect oxygen binding curve?
Increasing amount of BPG
Decreases affinity of Hb for oxygen
Curve shifts to the right
110
How does CO2 and H+ affect oxygen binding curve?
Decreases affinity of Hb for oxygen
| Curve shifts to the right
111
How does CO affect oxygen binding curve?
Carbon monoxide binds tightly to Hb
| Prevents oxygen binding
112
What catalyzes nearly all chemical reactions in the body?
Enzymes
| Protein catalysts
113
What does lactase do?
Hydrolysed lactose into glucose and galactose
114
What does DNA polymerase do?
Polymerises nucleotides to form DNA
115
Name 6 classes of enzymes
```
Transferases
Hydrolases
Oxidoreductases
Lyases
Isomerases
Ligases
THOLIL
```
116
Role of oxidoreductase enzymes
Oxidation-reduction reactions
| Transfer of electrons
117
Role of transferase enzymes
Transfer C-,N- or P- containing groups
118
Role of hydrolases
Catalyse cleavage of bonds by the addition of water
119
Role of lyase enzymes
Addition or removal of groups to form double bonds
120
Role of isomerases
Transfer of groups within molecules to form isomers
121
Role of ligase enzymes
Formation of bonds between C and O, S and N, at the expense of ATP
122
What is a cofactor?
Prosthetic group
Inorganic ion
E.g. Fe2+, Mn2+
123
What are coenzymes?
Prosthetic group
Organic compounds
Act as temporary carriers of groups in reaction
E.g. NAD, CoA
124
What is NAD?
Nicotinamide Adenine Dinucletide
| Coenzyme
125
What is CoA?
Coenzyme A
126
Examples of prosthetic groups
Coenzymes
| Cofactors
127
What are prosthetic groups?
Tightly or covalently linked to enzyme protein
| Additional chemical components to catalyse reactions
128
Properties of enzymes
Highly specific
Increase rate of reaction
Left unchanged after reaction has occurred
129
Explain specifity of enzymes
Interact with one or only a few substrates
| Catalyse one type of reaction
130
How do enzymes affect equilibrium of a reaction?
They don't.
131
How do enzymes work?
Lower activation energy for reaction to occur
Substrate bind to active site on enzyme
Increase local concentration of reactants
Stabilised formation of high energy transition state
132
What is an active site?
Site of reaction on enzyme
Coded by few aa of the long polypeptide chain
Usually clefts or crevices in protein
133
Why is active site usually crevice/cleft?
Allow substrate to bind
| Exclude water from reaction
134
What is the lock and key hypothesis?
Only molecules that have a complementary shape to the active site will be able to bind
Specificity of enzyme
135
What is the induced fit hypothesis?
Binding of substrate results in changes in shape of enzyme
| To enhance binding
136
How is substrate held in active site?
Multiple weak bonds with aa in this part of enzyme
137
What does the Michaelis Menten equation show?
How the reaction velocity v0 varies with the substrate concentration
138
What is v0?
Initial reaction velocity
139
What is the intercept at y-axis of a Lineweaver-Burk plot?
1/vmax
140
What is the slope of a Lineweaver-Burk plot?
Km/Vmax
141
What is the intercept at x-axis of a Lineweaver-Burk plot?
-1/Km
142
What are the axis of a Lineweaver-Burk plot?
X-axis 1/[S]
| Y-axis 1/V
143
How do irreversible enzyme inhibitors work?
Bind covalently to the enzyme molecule to destroy enzyme function
144
Types of reversible enzyme inhibitors?
Competitive and non-competitive inhibitors
145
How do competitive enzyme inhibitors work?
Binds at active site
Affects Km not Vmax
Can be overcome by increasing substrate concentration
146
How do non-competitive inhibitors work?
Bind at site other than the active site
Affects Vmax not Km
Cannot be overcome by increasing the substrate concentration
147
Define base
Nitrogenous base
Component of nucleic acid involved in base pairing
I.e. guanine (G), adenine (A), thymine (T), cytosine (C), uracil (U)
148
Define base pair (BP)
A pair of nitrogenous bases held together by hydrogen bonds
I.e. G-Cbase pair with 3 hydrogen bonds
And A-T base pair (or A-U base pair ) with 2 hydrogen bonds
149
Define chromatin
DNA, proteins and RNA needed to package DNA into the cell nucleus
'Loose' chromatin is 'bead on a string DNA'
Highly condensed chromatin is a chromosome
150
Define chromosome
Structure in the cell nucleus containing DNA wrapped around histones in a highly folded structured fashion
(1 double stranded DNA molecule or 2 identical double stranded molecules after DNA replication)
151
Define covalent modification
Addition of a chemical group to a protein
| Reversible covalent modification is often used as means of regulating the activity of enzymes and other proteins
152
Define DNA
Deoxyribonucleic acid
| Polymer of deoxyribonucleotides
153
Define genome
Total genetic content (DNA sequence) of an organism
| In case of diploid organisms the DNA sequence of one set of chromosomes
154
Define isoenzymes
Enzymes that catalyse the same reaction but have a different amino acid sequence
155
Define nucleoside
Nitrogenous base
| And a pentose sugar
156
Define nucleotide
Nitrogenous base
Pentose sugar
And a phosphate
157
Define nucleosome
Basic repeat unit of eukaryotic chromatin
| Bead-like structure formed by DNA wrapped around histones
158
Define phosphorylation
Addition of a phosphate group
159
Define protein kinase
Enzyme that can catalyse addition of a phosphate group from ATP to Ser/Thr/Tyr residues in a protein
160
Define protein phosphatase
Enzyme that catalyses removal of a phosphate group from Ser/Thr/Tyr residues in a protein
161
Define purine
Two-ring nitrogenous base
| E.g. Guanine (G) and Adenine (A)
162
Define pyrimidine
One-ring nitrogenous base
| E.g. Cytosine (C), thymine (T) and uracil (U)
163
Define RNA
Ribonucleic acid
| Polymer of ribonucleotides
164
Define zymogen
Inactive precursor of a proteolytic enzyme
165
What are the main forms of enzyme regulation?
Substrate and product concentration
Changes in enzyme conformation
Changes in the amount of enzyme
166
Ways to change enzyme conformation
Allosteric control
Covalent modification
Proteolytic activation
167
What is an allosteric enzyme?
Multi subunit enzymes that contain more than 1 active site for the substrate
168
What is positive cooperativity?
Binding of substrate to one active site enhances subsets binding to other active sites
169
What does an allosteric activator do to the Michaelis Menten curve?
Increases activity of enzyme
Curve shifted to the left
Shifts the R to T conformational equilibrium toward R
170
What does an allosteric inhibitor do to the Michaelis Menten curve?
Decreases activity of enzyme
Curve shifted to the right
Shifts the R to T conformational equilibrium toward T
171
Which enzyme catalyses attachment of a phosphate group?
Kinase
172
Which enzyme catalyses removal of phosphate groups?
Phosphatase
173
What is the an enzyme's inactive protein precursor known as?
Zymogen
174
How are zymogen a activated?
Removal of part of the polypeptide chain
| Many proteases produced in this form
175
What is a protease?
Enzyme that can break peptide bonds
176
How is premature proteolytic cleavage prevented?
Many proteases are produced in inactive zymogen form
Transported safely to sites of action
Then activated
E.g. Blood clotting factors
177
Ways to change amount of enzyme for regulation purposes?
Regulation of enzyme synthesis
| Regulated protein degradation
178
How is enzyme synthesis regulated?
Increasing or decreasing rate of transcription of mRNA
179
How is protein degradation regulated?
Proteins can be tagged for destruction by the addition of a small protein molecule known as ubiquitin
180
Ways to regulate metabolic pathways
Feedback inhibition
Feed forward activation
Counter regulation
181
What is feedback inhibition in metabolic pathway regulation?
End product of a pathway inhibits its own rate of synthesis by inhibiting enzymes earlier in the pathway
E.g. High [ATP] inhibit catabolic pathways
182
What is feed forward activation?
Increased amounts of initial substrate increases first step in pathway
E.g. High concentration of ethanol induce microsomal ethanol oxidising enzymes
183
How does counter regulation of metabolic pathways work?
If a catabolic pathway breaking down compound A is activated
Then the opposing anabolic pathway making compound A will be inactivated
E.g. Glycogenolysis and glycogenesis
184
Main mechanisms which regulate the blood clotting cascade
Inactive zymogens present at low concentration
Amplification of an initial signal
Localisation of clotting factors to the site of damage
Feedback activation by thrombin
Termination of clotting by multiple processes
185
How are clotting factors localised to site if damage?
Factor with Gla domains bind to damaged endothelial cell lining
Allow rapid activation of downstream effector molecules
186
Explain feedback activation by thrombin
Activated thrombin enhances conversion of
| Factor V, VII and XI to activated forms
187
Ways to terminate clotting
Removal of activated proteins
Proteolytic digestion
Binding of inhibitor molecules
188
Factors of extrinsic pathway
Factor VII
| Factor X
189
Factors of intrinsic pathway
```
Factor XI
Factor IX
VIII
V
Factor X
```
190
What is prothrombin converted to?
Thrombin
| By factor Xa
191
What is fibrinogen converted to?
Fibrin
| By thrombin
192
Which factor is necessary to form cross linked fibrin?
Factor XIIIa (activated by thrombin)
193
How many chromosomes do humans have?
23 pairs
194
Examples of polynucleotides
DNA
| RNA
195
What links nucleotides?
Covalent phosphodiester bonds
196
Molecule at 5' end?
Free phosphate
197
Molecule at 3' end
Free OH- group
198
Conventionally, which way is DNA strand written?
5' to 3'
199
Mutation in CF
3bp deletion (
200
Mutation in SCA
A>T
Glu>Val
In human beta haemoglobin protein
201
What is achondroplasia ?
Form of short limbed dwarfism
202
Mutation in achondroplasia
G>A
GLY>Arg
In cDNA of fibroblast growth factor gene
203
Mutation in PKU
G>A
Premature stop codon
Unstable mRNA transcript
Of human phenylalanine hydroxylase gene
204
Define allele
Alternative form of a gene
Each individual has two alleles for every gene
which can either be the same or different
205
Define autosome
Chromosome other than the sex chromosomes
| I.e. human chromosome 1-22
206
Define centromere
Region of a duplicated chromosome where two sister chromatids touch
Region of a chromosome to which the micro tubule spindle attach during cell division
207
Define chiasmata (pl chiasmata)
Point where two chromatids exchange genetic information during crossing-over in meiosis
Only when 2 non-sister chromatids (chromatids from different homologous chromosomes within a chromosome pair) exchange information will there be a genetic consequence
208
Define chromatid
One of two identical components of a duplicated chromosome
| Each containing a single (identical) double stranded DNA molecule
209
Define dominant
Phenotypic trait is dominant when it occurs in both homozygotes and heterzygotes
210
Define gene
Unit of heredity
Transcription unit
Length of DNA on a chromosome that contains the code for a protein (or RNA)
And sequences necessary for its expression e.g. Promoter and terminator sequences and introns
211
Define genotype
Genetic make-up of an individual
| Either as a whole or for one specific genetic locus
212
Define heterozygous
Having two different alleles for a specific genetic locus
213
Define homozygous
Having two identical alleles for a specific genetic locus
214
```
Define locus (pl loci)
Or genetic locus or gene locus
```
Specific position on a chromosome
215
Define meiosis
Process of cell division by which gametes are produced
216
Define mitosis
Process of cell division for somatic cells
217
Define phenotype
All observable characteristics of an individual
| The observable trait as a result of genetic make-up of one (or more) specific gene locus (loci)
218
Define recessive
Phenotypic trait is recessive when it occurs in homozygotes only
219
Define somatic cell
Cell other than the gametes
220
Stages in the cell cycle
G1
S
G2
M
221
What happens in G1?
Cell prepares for DNA replication
| Cellular contents, excluding the chromosomes are duplicated
222
What happens in the S phase?
Semi-conservative DNA replication
| Each of the 46 chromosomes is duplicated by the cell
223
What happens in G2 phase?
Cell prepares for cell division
| The cell 'double checks' the duplicated chromosomes for error making any needed repairs
224
What happens in M phase?
Cell division (mitosis)
225
What substrates are used by the enzyme DNA polymerase?
Deoxyribonucleoside triphosphate (dNTP)
226
What reaction is catalysed by DNA polymerase?
(dNMP)n + dNTP -> (dNMP)n+1 + PPi
| 5' to 3' chain growth
227
What is semi-conservative DNA replication?
Each strand of the parent molecule is maintained in the two daughter molecules
228
What does DNA helicase do?
Unravels the DNA double helix
229
What are Okazaki fragments?
DNA fragments of the lagging strand which is made discontinuously
230
What does DNA ligase do?
Joins the Okazaki fragments
231
Which strand is synthesised continuously in DNA replication?
Leading strand
232
Composition of human somatic cells
Diploid
23 pairs of chromosomes
(22 pairs of autosomes and 1 pair of sex chromosomes XX/XY)
233
Composition of human gametes and examples
Sperm and egg
Haploid
One set of 23 chromosomes
234
Chromosome properties after replication
Classical X-shape
| Two identical sister chromatids joined by centromere
235
What is the centromere?
Region of a chromosome that joins two identical sister chromatids
236
How many daughter cells produced after mitosis?
2 diploid cells
| Each have same chromosomal content as parent cell
237
How many daughter cells produced after meiosis
4 haploid cells
| Each has half the number of chromosomes as the parental cell
238
What happens during meiosis?
Diploid cell undergoes
One round of replication
Two rounds of division (meiosis I and meiosis II)
239
Why does mitosis take place?
Growth
| Maintenance
240
What is the M phase?
Mitosis
241
Steps of mitosis
```
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis
```
242
What happens in prophase?
Break down of nuclear membrane
Spindle fibres appear
Chromosomes condense
243
What happens in prometaphase?
Spindle fibres attach to chromosomes
| Chromosomes condense
244
What happens in metaphase?
Chromosomes align
245
What happens in anaphase?
Centromeres divide
| Sister chromatids move to opposite poles
246
What happens in telophase?
Nuclear membrane reforms
| Chromosomes decondense
247
What happens in cytokinesis?
Cytoplasm divides
| Parent cell become 2 daughter cells with identical genetic information
248
What do all people in a horizontal line in a pedigree have in common?
Same generation
249
What are the main patterns of inheritance?
```
✔Autosomal recessive
✔Autosomal dominant
Sex-linked inheritance
✔X-linked recessive/dominant
Y-linked
```
250
What is autosomal inheritance?
When the gene in question is located on an autosome
251
What is sex-linked inheritance?
When the gene in question is loaded on a sex chromosome
252
What is X-linked inheritance?
When gene in question is located on the X-chromosome
| Sex-linked inheritance
253
What is Y-linked inheritance?
When gene in question is located on the Y-chromosome
Inherited directly from father to son
Sex-linked inheritance
254
Unaffected Male
| In pedigree
White Square
255
Unaffected female
| In pedigree
White circle
256
Affected individual
| In pedigree
Black
257
Carrier
| In pedigree
Half black shading
| Or black dot in centre
258
Deceased individual
| In pedigree
/
| Through symbol
259
Unknown sex
| In pedigree
Diamond
260
What are linked genes?
2 genes close together on the same chromosome
Don't show independent assortment during meiosis
They co-segregate
261
How can linked alleles separate during meiosis?
Crossing-over
| Recombination
262
Define anticodon
Three nucleotides on tRNA molecule that are complimentary to a codon on the mRNA template
263
Define codon
Three nucleotides on mRNA molecules that code for a specific amino acid in the protein sequence
(Except stop codon)
264
What is a stop codon?
Does not code for an amino acid
| Signals termination of polypeptide chain growth
265
Define genetic code
Universal 'conversion table' from DNA information into amino acid information
I.e. how sets of three nucleotides (codons) encode the information for the different amino acids
266
Define mature mRNA
End product of transcription
I.e. after capping, polyadenylation and splicing has occurred
Serves as template in translation
267
Define ORF
Open reading frame
| A area of gene that holds code for all amino acid residues of the gene product (the protein)
268
Define promoter
Area of gene upstream of the ORF which regulates transcription
And therefore gene expression
Include sequences for binding of transcription factors and FNA polymerase and many regulatory factors (activators and repressors)
269
Define ribosome
Two-unit particle composed of many protein and ribosomal RNAs
Site of protein synthesis
270
mRNA
Messenger RNA
271
rRNA
Ribosomal RNA
272
tRNA
Transfer RNA
273
Define transcription
Process by which the DNA 'transcribed' ('copied') into RNA message
274
Define transcription initiation
Start of mRNA production
| Dependent on RNA polymerase binding
275
Define transcription termination
End of mRNA production
| Which is sequence dependent
276
Define translation
Process by which RNA message is 'translated' into an amino acid code (protein)
277
Define translation initiation
Start of protein production
| I.e. at the AUG codon
278
Define translation termination
End of protein production
| I.e. at a stop codon (UAA, UAG, UGA)
279
Where is mRNA made, what is this process called?
Nucleus
Transcription
DNA to mRNA
280
Where is protein made?
Cytoplasm
Translation
mRNA to protein
281
What are the three phases in transcription process?
Initiation
Elongation
Termination
282
What happens in initiation of transcription process?
Promoter recognition
| And binding
283
What happens in elongation of transcription process?
Actual process of 'transcribing' by RNA polymerase
284
What happens in termination of transcription process?
Sequence-dependent termination of RNA chain growth
285
Post-transcriptional processes
Transform pre-mRNA into mature mRNA
Capping
Tailing
Splicing
286
What is capping?
Addition of 5' cap
287
What is tailing?
Polyadenylation
| Addition of 3' polyA tail
288
What is splicing?
Removal of introns
| Exons 'spliced together'
289
What are the types of RNA?
rRNA ribosomal 80+%
mRNA messenger
tRNA transfer
290
What codon is AUG?
Methionine
291
What is the initiation codon?
AUG
| Methionine
292
What are the stop codons?
UAA
UAG
UGA
293
What are the three phases in the translation process?
Initiation
Elongation
Termination
294
What happens in the initiation process of translation?
AUG codon recognition and binding
| And formation of functional ribosome
295
What happens in the elongation process of translation?
Actual process of 'translating' the RNA message into protein
mRNA read codon by codon from 5' to 3'
While polypeptide chain growth is from amino to carboxyl terminus
296
What happens in the termination process of translation?
Stop codon recognition and dissociation of ribosome
297
Define glycosylation
Attachment of carbohydrate groups (oligosaccharide) to protein (side chain of certain aa residues) via glycosidic linkages
Can be N-linked (via amino side chains of Asn residues)
Can be O-linked (via hydroxyl side cabins of Ser/Thr residues)
298
Define preproprotein
Protein containing both a signal peptide and a propeptide
299
Define proprotein
Inactive precursor of a protein
| To become fully active the protein must undergo limited proteolytic to remove the propeptide
300
Define protein targeting
Mechanisms involved in directing proteins to their correct site of action inside (or outside) the cell
301
Define scurvy
Disease caused by vitamin C (ascorbic acid) deficiency that results in inadequate formation of hydroxyproline residues in collagen, reducing the stability of the collagen fibres
302
Define signal peptidase
Enzyme that removes the signal peptide from secretory proteins after entry into the ER
303
Define signal peptide
Short N-terminal peptide sequence that directs a newly formed secretory or membrane protein into the ER
304
Define signal recognition particle
Complex containing protein and RNA that binds the signal peptide of newly synthesised secretory proteins and escorts it to the ER for translocation
305
Define tropocollagen
Collagen triple helices formed extracellularly where the N- and C-terminal regions have been removed
306
Which proteins are more likely to be made on ribosomes on the ER?
Proteins destined for insertion into the plasma membrane, lysosomes, Golgi/ER or secretion
307
What addition do secreted proteins have?
Signal sequence at the N-terminus that targets them to the ER
308
What do signal sequences contain?
10-15 hydrophobic residues
1+ positively charged residues near amino terminus before hydrophobic sequence
Few polar amino acids in the C-terminal region
309
Protein secretion pathway part 1 - signal sequence
1 Protein synthesis initiated on free ribosomes
2 N-terminal signal sequence produced
3 Signal sequence of newly formed protein is recognised by the signal recognition particle (SRP)
310
Protein secretion pathway part 2 - SRP
4 GTP-bound SRP directs the ribosome synthesising the secretly protein to SRP receptors on the cystolic face of the ER
5 SRP dissociates
311
Protein secretion pathway part 3
6 Protein synthesis continues and the newly formed polypeptide is fed into the ER via a pore in the membrane (peptide translocation complex)
7 Signal sequence removed by a signal peptidase
8 Ribosome dissociates and is recycled
312
Modification to proteins in lumen of ER
Disulphide bond formation
| Glycosylation
313
N-linked glycosylation
Carbohydrate added via N-glycosyl link to amide nitrogen of Asn
Occurs in ER
314
O-linked glycosylation
Carbohydrate added via glycosidic link to hydroxyl of Ser or Thr
Occurs mainly in Golgi
315
Types of secretion
Constitutive secretion
| Regulated secretion
316
What is constitutive secretion?
Continuous process
Not regulated
Proteins packaged into vesicles and release continuously by exocytosis
E.g. Serum, albumin, collagen
317
What is regulated secretion?
Proteins released in response to a signal/ stimulus e.g.hormone
Proteins packaged into vesicles but not released until stimulus received e.g. Insulin
320
What cuts pro insulin into 3 peptides?
Proteases
321
Biosynthesis of collagen part 1
1 Synthesis and entry of chain into lumen of rough ER
2 Cleavage of signal peptide
3 Hydroxylation of selected proline and lysine residues
4 Addition of N-linked oligosaccharides
5 Addition of galactose to hydroxylysine residues
322
Biosynthesis of collagen part 2
6 Chain alignment, formation of disulphide bonds
7 Formation of triple helical pro collagen from C- to N- terminus
8 Completion of O-linked oligosaccharide chains by addition of glucose
323
Biosynthesis of collagen part 3
9 Transport vesicle
10 Exocytosis
11 Removal of N- and C- terminal peptides
324
Biosynthesis of collagen part 4
12 Lateral association of collagen molecules followed by covalent cross-linking
13 Aggregation of fibrils
325
Define antibody
Protein which is produced by the body in response to a foreign compound (antigen) usually a protein.
Antibodies can be used diagnostically to detect specific proteins.
326
Define cloning
Production of exact copies of a piece of DNA
327
Define cloning vector
DNA molecule such as a plasmid, virus or artificial chromosome into which a piece of foreign DNA can be added for cloning
328
Define ELISA
Enzyme-linked immunoabsorbent assay
Technique using an antibody linked to an enzyme used to quantify the amount of a molecule
Used in diagnostic tests to measure the concentration of biological molecules in solution
329
Define gel electrophoresis
Technique which separates macromolecules (proteins/DNA/RNA) on the basis of their size or charge
Molecules are separated in gel and migrate due to the presence of an electric charge played across the gel
330
Define PCR
Polymerase chain reaction
Very powerful and sensitive technique whereby small fragments of DNA are amplified using a DNA (or RNA) template
Amount of template needed is minute
Amount of amplified DNA end-product is enormous
Enough for further experimental procedures
E.g. Gene cloning, restriction analysis and DNA sequencing
331
Define primer
Short oligonucleotide (10-25nt)
Can be 3'-extended by DNA polymerase
Primers of specific sequence used in molecular techniques like PCR and DNA sequencing
332
Define restriction endonuclease (restriction enzyme)
Enzyme that recognises and cuts double stranded DNA at a specific sequence (the restriction site)
333
Define restriction site
Sequence of DNA that can be recognised by a restriction endonuclease
Enzyme can then specifically cut the double stranded DNA molecule within (or adjacent to ) the recognition sequence
334
Define SDS-PAGE
Sodium dodecyl sulphate polyacrylamide gel electrophoresis
Gel electrophoresis of proteins in the presence of the detergent SDS
Proteins are separated on the basis of their size
335
Define western blotting
Technique where a protein separated by electrophoresis is transferred to a membrane filter and is detected by the binding of an antibody directed against it
336
Techniques for DNA analysis at gene level
Restriction analysis/ gene cloning
Gel electrophoresis
Polymerase chain reaction
353
How many disulphide bonds does insulin have?
3 disulphide bonds
Formed in pro insulin
Eer sent in mature insulin too
357
Proteolytic processing of insulin
Preproinsulin
= pro insulin + signal sequence
= mature insulin + C peptide
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