Book 1: Human molecular genetics Flashcards
(326 cards)
1
Q
How many macromolecules exist in molecule genetics?
A
3.
2
Q
Which are the 3 macromolecules that define molecular genetics?
A
- Proteins.
- DNA.
- RNA.
3
Q
What is DNA in organisms?
A
The genetic material.
4
Q
What is the function of DNA?
A
Transmitted to daughter cells when cells replicate.
Transmitted from generation to generation when organisms reproduce.
5
Q
What do viruses have?
A
Genetic material.
6
Q
Where is virus’ genetic material transmitted?
A
To viral progeny.
7
Q
What are the types of virus’ genetic material?
A
DNA.
RNA.
8
Q
On what does the type of virus’ material depend?
A
On the virus’ type.
9
Q
What is the genome of an organism?
A
Different DNA molecules set.
10
Q
What do all the proteins have?
A
A polypeptide core.
11
Q
How is the polypeptide core of proteins synthesized?
A
By using genetic information in DNA molecules.
12
Q
How is the genetic information stored in cells?
A
In DNA molecules.
13
Q
Why are genetic information stored in DNA and not in RNA anymore?
A
DNA is more chemically stable.
It can be copied accurately.
Transmitted to daughter cells and to generations.
14
Q
Where are DNA molecules found in eukaryotes?
A
In the chromosomes of nucleus.
Mitochondria.
15
Q
Where is the DNA stored in plants?
A
In chloroplasts.
16
Q
What are genes?
A
Segments of hereditary DNA/RNA molecules.
17
Q
What do genes make?
A
A polypeptide.
A mature functional RNA.
18
Q
What do polypeptides and RNA molecules make?
A
Working molecules.
19
Q
With what molecules are polypeptides complexed?
A
Carbohydrates.
Lipids.
Other polypeptides.
20
Q
How is the DNA packed in simple organisms?
A
With genes.
21
Q
How are genes packed in more complex eukaryotic cells?
A
Distributed within DNA.
22
Q
Of what does DNA consist in multicellular eukaryotes?
A
Of repetitive sequences.
23
Q
How is a coding RNA sequence called?
A
Messenger RNA (mRNA).
24
Q
What is the function of mRNA?
A
Carries information from DNA to protein synthesis.
25
Where is mRNA made?
In nucleus.
26
Where is mRNA exported?
In cytoplasm.
27
Why is MRNA exported in cytoplasm?
To make proteins.
28
Where else can mRNA synthesise proteins?
In mitochondria.
| Chloroplasts.
29
What is the characteristic of noncoding RNA sequences?
Second class of RNA.
Not used as template to make polypeptides.
Act in general way.
Regulate small genes' expression.
30
What do proteins represent?
The major DNA endpoint information.
31
How does genetic information generally flow?
In a one-way direction.
32
Why is DNA encoded?
To make RNA.
33
Why is RNA coded?
To make polypeptides.
34
What do polypeptides form?
Proteins.
35
Why the flow of genetic information has been described as the central dogma of molecular biology?
Because of its universality.
36
How many sequential processes are essential in all cellular organisms?
2.
37
Which are the 2 processes essential in organisms?
1. Transcription.
| 2. Translation.
38
What happens in transcription?
A sequence of bases on a DNA strand is used as a template --> RNA polymerase --> synthesises RNA.
RNA product --> makes mRNA.
39
What happens in translation?
mRNA is decoded --> makes polypeptides at ribosomes.
40
Where are large RNA-protein complexes found?
In cytoplasm.
In mitochondria.
In chloroplasts.
41
Where is genetic information encoded?
In linear sequence of nucleotides in DNA.
42
When is genetic information copied?
During transcription.
43
Why is genetic information copied during transcription?
To specify a linear sequence of nucleotides in RNA product.
44
What is read in a linear sequence to specify amino acids' sequence in polypeptide product?
3 nucleotides at a time = codons.
45
What do RNA viruses have?
An RNA genome.
| A gene that makes reverse transcriptase.
46
What happens in a reverse transcriptase of RNA viruses?
DNA polymerase uses RNA template --> make DNA sequence copy.
47
What do many DNA sequences in our cells specify?
Reverse transcriptase.
48
Why do many DNA sequences in our cells have reverse transcriptase?
To allow DNA copies to be made from different RNAs.
49
Where is the reverse flow of genetic information from RNA to DNA important?
In the evolution of our genome.
| Replication of DNA sequences at end of linear chromosomes.
50
What do all proteins have?
A linear polypeptide backbone with carbohydrate, lipid, and small chemical groups added.
51
What are DNA and RNA strands?
Large polymers.
| With very similar structures.
52
What does each of DNA and RNA strands have?
A linear sugar-phosphate backbone.
Alternating parts of a five-carbon sugar and a phosphate.
A nitrogenous base attached to each sugar part.
53
What are the sugars in RNA and DNA?
RNA sugar: ribose.
| DNA sugar: deoxyribose.
54
What is the difference between DNA and RNA sugars?
Lack (DNA)/possessing (RNA) -OH group at 2'-carbon positions.
55
What does identify the nucleic acid and determine its function?
Sequence of bases.
56
Of what do the bases of a nucleic acid consist?
Heterocyclic rings: carbon + nitrogen atoms.
57
What are the 2 structural classes bases are divided into?
1. Purines.
| 2. Pyrimidines.
58
What do purines have?
2 interlocked rings.
59
What do pyrimidines have?
A single ring.
60
What are there in both DNA and RNA?
4 principal base types.
2 purines.
2 pyrimidines.
61
Which are the common bases in both DNA and RNA?
Adenine.
Cytosine.
Guanine.
62
Which is the fourth in each of DNA and RNA?
DNA: Thymine.
RNA: Uracil.
63
What is the difference between thymine and uracil?
Uracil lacks 5-methyl group found in thymine.
64
To what is each base attached in nucleic acids?
To sugar.
65
How is each base attached to a sugar in nucleosides?
By an N-glycosidic bond.
66
What does N-glycosidic bond join in nucleosides?
A nitrogen to carbon 1' of sugar.
67
What is a nucleoside?
Sugar attached to a base.
68
What is the basic repeat unit of a DNA strand?
A nucleoside with a phosphate group attached at 5' or 3' carbon of sugar.
69
How is the nucleoside with a phosphate group attached at 5' or 3' carbon of a sugar called?
A nucleotide.
70
What else does DNA contain?
Minor base.
71
By what are minor base types produced?
Chemical modification.
72
By what are proteins composed?
One/more polypeptide chains.
73
How can polypeptide chains be modified?
BY addition of carbohydrate side chains.
| Other chemical groups.
74
What are polypeptides?
Polymers.
75
What do polypeptides have?
A linear sequence of repeating units.
76
How are the repeating units of polypeptides called?
Amino acids.
77
What happens to amino acids in their electrically neutral form?
Amino group connected by a-carbon atom to carboxyl group.
78
What does an identifying side chain determine in amino acids?
Their chemical nature.
79
What does the amino group gain at neutral pH?
A proton.
80
How does the amino group become once it gains a proton at neutral pH?
Positively charged.
81
What does the carboxyl group of amino acids lose at neutral pH?
A proton.
82
How does the carboxyl group of amino acids become once it loses a proton at neutral pH?
Negatively charged.
83
What does a polypeptide have?
A repeating backbone.
84
What happen on the repeating backbone of polypeptides?
Amino acids linked by amide groups by peptide bonds.
85
Into how many groups can the 20 different amino acids be classified?
3 main groups.
86
What do covalent bonds require to break?
High energy input.
87
How can noncovalent bonds break?
At physiological temperatures.
88
When are hydrogen bonds formed?
When H+ interacts with electron atoms: O2/Ni.
89
Where do ionic interactions occur?
Between charged groups.
90
Where are ionic interactions weak and when strong?
```
Weak = in aqueous environments.
Strong = in crystals.
```
91
Where are ionic bonds important?
In biological function.
| Enzyme-substrate recognition.
92
What do Van der Waals forces show?
Weak attractive bonding interaction.
93
Why do Van der Walls force have weak bonding?
Due to electrical charges.
94
What happens when atoms become extremely close?
Knockout each other strongly.
95
Where can Van der Walls forces be important?
Between surfaces of 2 macromolecules.
96
What is the cellular environment?
Aqueous.
97
What is the structure of water?
Complex.
98
What does the water structure include?
Rapid network.
| Noncovalent bonding.
99
What is the most important force in water molecules?
Hydrogen bond.
100
What is hydrogen bond?
Weak.
| Electrostatic.
101
Where does hydrogen bond occur?
Between positive hydrogen atoms and negative atoms.
102
What is a characteristic of charged molecules?
highly soluble in water.
103
What are DNA and RNA based on the phosphate groups of their nucleotides?
Negatively-charged polyanions.
104
What can proteins be based on their amino acid composition?
Neutral.
Positive.
Negative.
105
When are neutral proteins soluble?
If they contain charged/neutral polar amino acids.
106
Wat are the membrane-bound proteins with many hydrophobic amino acids, in a hydrophobic encironment?
Thermodynamically more stable.
107
What do noncovalent bonds allow?
Interactions between different molecules.
108
Why is hydrogen bonding important?
It allows interactions between different nucleic acids.
| Facilitates recognition by regulatory RNAs of target sequences in other rRNAs/DNA.
109
How are neighbouring sugars linked?
By 3'- 5' phosphodiester bonds.
110
What happens in 3'- 5'phosphodiester bonds?
Phosphate group links 3' carbon of one sugar to 5' carbon of next sugar-phosphate backbone.
111
What is the genetic material of viruses?
Single-stranded DNA.
112
How many species does each cellular DNA species have?
2 DNA strands.
113
How are the 2 DNA strands structured?
As a double helix.
114
What happens in the double helix?
Strands curve around each other.
115
How is base pair structured?
Each base on one DNA = non-covalently linked to opposed base on opposite DNA strand.
116
What does base pairing involve?
Certain purine-pyrimidine combinations only.
117
When doe the 2 DNA strands fit together correctly in double- stranded DNA?
When opposite every A on one strand is a T on the other strand and when opposite every G is a C.
118
Which base pairs are accepted in DNA?
A-T.
| G-C.
119
By how many hydrogen bonds are base pairs held together in the Watson-Crick model of DNA?
G-C: 3 bonds.
| A-T: 2 bonds.
120
Which bonds are stronger in the DNA molecule?
The 3 hydrogen bonds between G-C pairs.
121
How is the base composition of DNA measured?
Amount of A% = amount of T%.
Amount of G% = amount of C%.
Total = 100%.
122
What does a nucleic acid strand have?
Asymmetric ends.
5' end C not linked to another sugar.
3' end C not involved in phosphodiester bonding.
123
What is the orientation of each nucleic acid strand?
5' --> 3'.
124
In what orientation must 2 strands which form a duplex be?
In an antiparallel arrangement.
125
What do we mean by 'antiparallel arrangement of duplex DNA'?
5' --> 3' direction of one DNA strand = opposite to its partner's orientation.
126
Why are the hydrogen bonds formed in base pairing important?
They form a double helix.
127
Why are the base-stacking forces important?
They stabilise the helix between adjacent bases.
128
What are the characteristics of double helix?
Rigid.
| Uniform structure
129
What can double helix undergo?
Local changes.
| Alternative base pairing types.
130
Which base pairs can make the minor groove of double helix narrower?
A-T base pairs.
131
What is an alternative type of double helix that can be formed?
Z-type DNA double helix.
132
What can the base pairs in DNA adopt?
Different geometries.
133
What is an example of different geometry of base pairs in DNA?T
Flipped base pairing --> rotation of bases close to 180 degrees around N-glycosidic bond --> forms Hoogsteen base pairs.
134
What are the telomeres?
The specialised sequences at the ends of linear chromosomes.
135
What are the cytokine modifications?
Epigenetic marks important for regulating gene expression.
136
For how much distance do bases show perfect matching in a double-stranded DNA in humans?
Over 249 million nucleotides.
137
What do the 2 DNA strands of a duplex exhibit?
Base complementarity.
138
What do the 2 DNA strands of a duplex have?
Complementary base sequences.
139
By what is the genetic information encoded?
By the linear sequence of bases in DNA strands.
140
How are nucleic acids defined?
By their base sequences.
141
In which direction are base sequences written?
In the 5'-->3' direction.
142
What is the 5' --> 3' direction about?
The direction of synthesis of new DNA/RNA from a DNA template.
143
How must the sequence of a single-stranded oligonucleotide be written?
Accurately: 5' p-C-p-G-p-A-p-C-p-C-p-A-p-T-OH 3'.
144
How can we make a complementary DNA strand: 3' --> 5'?
By the template strand (given): 5' --> 3'.
145
How is DNA replication characterised?
Semi-conservative.
146
What must happen to each double-stranded DNA before cell divide?
They must be replicated.
147
Why must each double-stranded DNA be replicated before cells divide?
To generate 2 identifiable double helices, 2 daughter cells.
148
What must happen first in DNA replication?
The 2 DNA strands of original double helix --> unwound.
149
How can the 2 DNA strands be unwound?
By a DNA helicase.
150
What happens to the 2 unwound DNA strands?
Each is used as a template by a DNA polymerase.
151
What does each template strand make?
A complementary DNA strand.
152
How are the complementary strands made?
With 4 deoxy nucleoside triphosphates: dNTPS.
153
What is dNTPS?
A combination of dATP, dCTP, dGTP, and dTTP.
154
What does the DNA Polymerase do?
Cleaves the dNTP precursors between first and second phosphates.
155
How is DNA synthesis initiated?
By using an RNA primer and a specialised primase enzyme.
156
What happens in DNA synthesis?
The new DNA chain grows.
157
How does the new DNA chain grow?
By adding nucleotides one at a time to the 3'.
158
How are nucleotides added to make the new DNA strand?
By using a DNA-dependent DNA polymerase and dNTPS.
159
How is the DNA synthesis reaction driven?
By the change in free energy when dNTP is cleaved at phosphoanhydrite bond between first and second phosphate.
160
Of what does the parental duplex consist?
Of 2 complimentary DNA strands.
161
What does each completed daughter DNA duplex contain?
One of the 2 parental DNA strands + one newly synthesized DNA strand.
162
To what is each completed daughter DNA duplex identical?
To each other and to the original parental DNA duplex.
163
How is DNA replication characterised due to the fact that each daughter duplex has one strand from the original DNA and one new DNA strand?
Semi-conservative.
164
How are the specific points, DNA replication is initiated called?
Origins of replication.
165
What is the overall direction of chain growth for one newly synthesized daughter strand?
5'-->3'.
166
What is the direction for the lagging strand?
3' --> 5'.
167
What do the reactions catalysed by DNA polymerase involve?
Adding dNMP residues to the free 3' hydroxyl group of the growing DNA strand.
168
What does the leading strand always have?
A free 3' hydroxyl group that allows continuous elongation in the same direction as the replication moves.
169
Why is a DNA helicase needed?
To open up a replication fork.
170
What does DNA helicase allow?
Synthesis of new daughter DNA strands to begin.
171
Why is replication discontinuous?
Because lagging strand is synthesized in the opposite direction and is built up in pieces, Okazaki fragments.
172
What happens to the Okazaki fragments?
They will be stitched together with a DNA ligase.
173
What does the initiation of the leading strand and of each Okazaki fragments of the lagging strand require?
A short RNA primer synthesized and base-paired with the original DNA strand.
174
What will happen to the RNA primers after replication?
Will be removed and replaced by a DNA sequence.
175
What is the direction of synthesis of the lagging strand?
Opposite to replication fork direction.
176
What is the difference between RNA polymerases and DNA polymerases?
DNA polymerases need a primer with a free 3' hydroxyl end to initiate synthesis.
177
How many RNA primers are needed when synthesizing the leading strand?
Just one.
178
What happens due to the fact that synthesis of the lagging strand is discontinuous?
An RNA primer is needed to initiate the synthesis of each Okazaki fragment.
179
Where does the machinery for DNA replication rely?
On a variety of proteins and RNA primers.
180
How many DNA polymerases do mammalian cells have?
20.
181
What do DNA polymerases in our cells use?
An individual DNA strand as a template for synthesizing a complementary DNA strand.
182
What do RNA-directed DNA polymerases use in our cells?
RNA templates to make complementary DNA sequences.
183
How are RNA-directed DNA polymerases called?
Reverse transcriptases.
184
What do DNA-directed DNA polymerases include?
DNA polymerases delta and epsilon to copy accurately DNA sequences.
185
What do DNA polymerases do?
Replicate most of the nuclear DNA of our cells.
186
What does polymerase delta synthesize?
The lagging strand.
187
What does polymerase epsilon synthesize?
The leading strand.
188
What do the delta and epsilon enzymes have?
Low error rates.
189
Why do delta and epsilon polymerases have low error rates?
Because they have an associated 3' -5' exonuclease activity responsible for proofreading.
190
What do the epsilon and delta polymerases do in proofreading?
If a mistake is made --> wrong base is inserted at 3' hydroxyl group of growing DNA chain --> 3' -5' exonuclease snips it out --> the correct base is inserted.
191
What does initiation of DNA replication and of Okazaki fragments require?
DNA polymerase alpha.
192
What id the DNA polymerase alpha?
polymerase complex + primase.
193
What does DNA polymerase alpha lack?
Own proofreading function.
194
What happens in polymerase alpha?
Errors made in base incorporation are corrected without needing polymerase delta.
195
What does DNA polymerase gama have?
An intrinsic proofreading exonuclease activity.
196
What does polymerase gama synthesize?
Mitochondrial DNA.
197
Where do DNA polymerases function?
Recombination and DNA repair.
198
Which are the major classes of proteins involved in DNA replication?
1. Topoisomerases.
2. Helicases.
3. Single-strand-DNA binding proteins.
4. Primases.
5. DNA polymerases.
6. DNA ligases.
199
What do topoisomerases do?
Break a single DNA strand --> release tension --> helix uncoiled form --> DNA unwound.
200
What do helicases do?
Unwind double helix at replication fork.
201
What do single-strand-DNA binding proteins do?
Maintain stability of replication fork.
| Protect single-stranded DNA from being degraded.
202
What do primases do?
Attach a primer to single-stranded DNA at replication fork.
203
What do DNA polymerases do?
Synthesize new DNA strands.
204
What do DNA ligases do?
Seal nicks that remain in newly synthesized DNA after RNA primers are removed and small gaps are filled in by DNA polymerase.
Catalyse information of a phosphodiester bond between unattached adjacent 3' OH and 5' phosphate groups.
205
What is RNA normally?
Single-stranded.
206
What do certain RNA viruses have?
A double-stranded RNA genome.
207
How can double-stranded RNA be formed by a single-stranded RNA genome?
Transcription of RNA sequences --> make a complementary RNA.
208
What do RNA molecules need to have?
RNA-RNA base pairing.
209
What do RNA sequences form when they engage with DNA sequences?
RNA-DNA duplexes.
210
When is an A-type double helix formed rather than the common B-type helix?
When a 2' hydroxyl group is present on ribose sugar of an RNA-RNA or an RNA-DNA duplex.
211
What is it important in shaping the structure of a single-stranded RNA?
Hydrogen bonding.
212
Where else is hydrogen bonding important in single-stranded RNA?
Functional, short, double-stranded sequence recognised by specific RNA-binding proteins.
213
What are the most common type of secondary structure?
Hairpin structures.
214
Of what is the genome in many viruses made up?
One type of nucleic acid: single-stranded DNA, double-stranded DNA, single-stranded RNA, double-stranded RNA.
215
How can viruses be classified?
+ viruses.
| - viruses.
216
Where do DNA viruses replicate?
In nucleus.
217
Where do RNA viruses replicate?
In cytoplasm.
218
What does RNA replication have higher than DNA replication?
Error rate.
219
What does the elevated mutation rate allow RNA viruses?
Adapt rapidly to changing environmental conditions.
220
What are the retroviruses?
RNA viruses.
221
Where do retroviruses replicate?
In nucleus.
222
Into what is the single-stranded RNA genome of retroviruses converted?
A single-stranded complementary DNA.
223
How is the single-stranded RNA genome of retroviruses converted into a single-stranded complementary DNA?
By using a viral reverse transcriptase.
224
What happens to the complementary DNA?
Converted into a double-stranded DNA.
225
How is cDNA converted into a double-stranded DNA?
By using a DNA polymerase from the host cell.
226
What do viral proteins do?
Help instert the double-stranded DNA into the genome of the host cell.
227
What happens to the double-stranded DNA once it enters the genome of the host cell?
It remains for long periods or is used to synthesize new viral RNA genomes packaged as new virus particles.
228
Where is DNA replication initiated?
At origins of replication.
229
What does DNA replication generate?
Y-shaped replication forks.
230
What happens in Y-shaped replication forks?
The parental DNA duplex is opened up.
231
What do the antiparallel parental DNA strands do?
Serve as templates for the synthesis of complementary daughter strands which run in opposite directions.
232
What is the direction of one newly synthesized daughter, leading strand?
5' --> 3'.
233
What is the direction of the other daughter lagging strand?
3' --> 5'.
234
What do the reactions catalysed by DNA polymerase involve?
Adding dNMP residues to the free 3' hydroxyl group of the growing DNA strand.
235
Which strand has a free 3' hydroxyl group that allows continuous elongation in the same direction where the replication fork moves?
Only the leading strand.
236
What does a DNA helicase do?
Opens up a replication fork --> synthesis of new daughter DNA strands begins.
237
How is replication characterised?
Semi-discontinuous.
238
Why is replication semi-discontinuous?
Lagging strand is synthesized in the opposite direction --> built up in pieces Okazaki fragments A, B, C.
Leading strand is synthesized continuously.
239
How will the Okazaki fragments stich together?
Using DNA ligase.
240
What are the Okazaki fragments?
100-1000 nucleotides joined by enzyme DNA ligase that make the lagging strand, in opposite direction of replication fork.
241
How is the leading strand synthesized?
Continuously.
242
Can DNA polymerases initiate synthesis?
No.
243
When can DNA polymerases initiate synthesis?
Only when a short oligonucleotide primer with a free 3' hydroxyl end is provided.
244
For what are RNA primers needed?
Initiating synthesis.
245
By what are RNA primers synthesized?
DNA primase.
246
How many RNA primers are needed in synthesis?
Only one.
247
What happens in synthesis of Okazaki fragments?
An RNA primer is needed to initiate synthesis of each fragment.
248
How will the RNA primer be removed?
With a 5' --> 3' exonuclease.
249
By what will the RNA primers replaced after synthesis?
By the corresponding DNA sequence.
250
On what does the machinery for DNA replication rely?
On proteins.
On RNA primers.
On evolution.
251
Where is DNA replication more compelx?
In eukaryotes.
252
How many DNA polymerases do mammalian cells have?
20.
253
What does each DNA polymerase have?
Special function.
254
What are most of the DNA polymerases in our cells?
DNA-directed.
255
What do DNA polymerases do in our cells?
Use an individual DNA strand as a template --> synthesise a complementary DNA strand.
256
What other polymerases do we have in our cells?
RNA-directed DNA polymerases.
257
How are RNA-directed DNA polymerases named?
Reverse transcriptases.
258
What do RNA-directed DNA polymerases do?
Use RNA templates --> make complementary DNA sequences.
259
How many structures does a double helix have?
3.
260
What are the 3 structures of the double helixes?
A-form.
B-form.
Z-form.
261
What is the difference between the A-form and the B-form?
A-form is shorter and wider.
| Has a deep, narrow major groove.
262
When does A-DNA structure exist?
Only under non-physiological conditions.
263
Where .can G-U base pairing occur?
In short regions of double-stranded RNA in the RNA strand.
264
Is the G-U base pairing stable?
No.
265
Does the G-U base pairing distort the RNA-RNA helix?
No.
266
What can DNA have?
Cell-type specific function.
267
Why can DNA have cell-type specific functions?
Because it contains sequences used to make RNA and polypeptides which differ from cell to cell.
268
What are genes?
Discrete DNA segments.
Spaced at irregular intervals in the DNA strand.
Serve as templates.
269
Why do genes serve as tmplates?
To make complementary RNA sequences in transcription.
270
What must the initial primary RNA transcript undergo?
Maturation steps.
271
Why must the primary RNA transcript undergo maturation steps?
To make the mature functional mRNA.
272
What does the mature mRNA do?
Serves as template --> makes a polypeptide.
273
What are the gene products needed for?
Vital cell processes = DNA Replication, protein synthesis.
274
When are proteins and RNA products made in specific cell types and not in all?
In B and T lymphocytes which make immunoglobulins and T-cell receptors.
275
What are the DNA compositions of the different cell types in an organism?
Identical.
276
Why is there variation in cells in an organism?
Because there are gene expression differences in transcription.
Different genes are transcribed.
277
On what does gene expression depend?
On cells' needs.
278
What does transcription mean?
RNA --> synthesized
| Using DNA-directed RNA polymerases.
279
What happens in transcription?
DNA strands = templates for RNA synthesis.
280
Where is RNA synthesized in eukaryotic cells?
In nucleus.
281
What is transcribed in eukaryotic cells?
Nuclear genes.
282
Where is a small amount of genes transcribed.
In mitochondria.
| Chloroplasts.
283
How are genes transcribed in mitochondria and chloroplasts?
DNA in organelles --> transcribed.
284
Where are chloroplasts found?
In plant cells.
285
What happens to the DNA during transcription?
DNA helix --> unwound locally --> separated DNA strand --> RNA polymerase comes --> makes a complementary RNA sequence.
286
Where is RNA polymerase and DNA polymerase used?
RNA Polymerase: Transcription.
| DNA Polymerase: DNA Replication.
287
What does the RNA transcript have?
A complementary sequence of the template DNA strand.
5' - 3' direction.
Base = U instead of T.
Base sequence as the nontemplate DNA strand.
288
How is the nontemplate called?
Sense strand.
289
How is the template strand called?
Antisense strand.
290
Which DNA strand is used by the RNA polymerase as a template to synthesize a complementary RNA strand?
The template strand.
291
From what is the RNA strand synthesized?
Ribonucleoside triphosphate precursors. (rNTPs).
292
What does the polymerase do to synthesize RNA?
Opens rNTPs --> gives Ribonucleoside monophosphates (rNMPs).
293
How are the rNMPs inserted?
One nucleotide as a time.
294
How are the rNMPs inserted?
Join the 3'OH of previous nucleotide based on base pairing rules.
295
On what is RNA transcription based?
Base Pairing rules.
296
On which DNA strand will the RNA strand be complementary and on which identical?
Complementary to the template strand.
Identical to the sense strand.
297
From which 4 precursors does RNA Polymerase synthesize RNA?
ATP, CTP, GTP, UTP.
298
What does elongation involve?
Addition of appropriate ribonucleotide monophosphate: AMP, CMP, GMP, UMP to 3'OH end of growing RNA strand.
299
How can transcription run ffectively?
Various proteins bind DNA sequence --> guide RNA Polymerase.
300
What is also important to be added in transcription?
DNA elements.
301
How many classes of DNA-dependent RNA polymerase occur in eukaryotic cells?
4.
302
Where are the 3 DNA-dependent RNA polymerase classes used?
Transcribing nuclear genes.
303
Where is the last DNA-dependent RNA polymerase used?
Transcribing mitochondiral DNA.
304
By what is the mitochondrial RNA polymerase encoded?
Nuclear gene.
305
How is the mitochondrial DNA transcribed?
Nuclear gene --> encoded --> mRNA --> cytoplasm --> ribosomes --> translation --> mitochondria.
306
What is the difference between DNA Polymerases and RNA polymerases?
RNA polymerases do not need primer to initiate RNA synthesis.
307
What do RNA polymerases need to start transcription process?
Protein regulators = transcription factors \.
308
What do transcription factors do?
Bind to certain DNA sequences with gene --> activate transcription process.
309
To what can a transcription factor bind?
To a promoter.
310
What is a promoter?
A collection of closely spaced short DNA sequence elements in a gene neighbourhood.
311
What do transcription factors activate once they bind to a promoter?
The RNA Polymerase.
312
Where are promoters and primase used?
Promoter: RNA Polymerase --> transcription.
Primer: DNA Polymerase --> DNA replication.
313
What are the transcription factors?
Trans-acting.
314
Why are the transcription factors trans-acting?
Because they are produced be remote genes --> migrate --> to sites of action.
315
What are the promoter sequences?
Cis-acting?
316
Why are the promoters cis-acting?
Because the are located on the same DNA molecule where they regulate the genes.
317
For what is the RNA polymerase 2 responsible?
Transcribing all protein coding genes in nucleus + important genes encoding noncoding RNAs.
318
Where does RNA polymerase 2 rely?
Transcription factors.
Tissue specific
Cell specific factors
319
Where does RNA Polymerase 1 occur?
Nucleolus.
320
What does RNA Polymerase 1 synthesize?
Cytoplasmic ribosomal RNAs.
321
Where does RNA polymerase occur?
Nucleoplasm.
322
What does RNA Polymerase 2 synthesize?
mRNAs nuclear genes + noncoding RNAs, snRNAs, miRNAs, IncRNAs, snoRNAs.
323
Where does RNA Polymerase 3 occur?
Nucleoplasm.
324
What does RNA polymerase 3 synthesize?
Small noncoding RNAs, ribosomal RNA, cytosolic tRNAs.
325
Where does RNA Polymerase mt occur?
Mitochondria.
326
What does RNA polymerase mt synthesize?
RNAs from mitochondrial DNA.
