Book 1: Human molecular genetics Flashcards
How many macromolecules exist in molecule genetics?
3.
Which are the 3 macromolecules that define molecular genetics?
- Proteins.
- DNA.
- RNA.
What is DNA in organisms?
The genetic material.
What is the function of DNA?
Transmitted to daughter cells when cells replicate.
Transmitted from generation to generation when organisms reproduce.
What do viruses have?
Genetic material.
Where is virus’ genetic material transmitted?
To viral progeny.
What are the types of virus’ genetic material?
DNA.
RNA.
On what does the type of virus’ material depend?
On the virus’ type.
What is the genome of an organism?
Different DNA molecules set.
What do all the proteins have?
A polypeptide core.
How is the polypeptide core of proteins synthesized?
By using genetic information in DNA molecules.
How is the genetic information stored in cells?
In DNA molecules.
Why are genetic information stored in DNA and not in RNA anymore?
DNA is more chemically stable.
It can be copied accurately.
Transmitted to daughter cells and to generations.
Where are DNA molecules found in eukaryotes?
In the chromosomes of nucleus.
Mitochondria.
Where is the DNA stored in plants?
In chloroplasts.
What are genes?
Segments of hereditary DNA/RNA molecules.
What do genes make?
A polypeptide.
A mature functional RNA.
What do polypeptides and RNA molecules make?
Working molecules.
With what molecules are polypeptides complexed?
Carbohydrates.
Lipids.
Other polypeptides.
How is the DNA packed in simple organisms?
With genes.
How are genes packed in more complex eukaryotic cells?
Distributed within DNA.
Of what does DNA consist in multicellular eukaryotes?
Of repetitive sequences.
How is a coding RNA sequence called?
Messenger RNA (mRNA).
What is the function of mRNA?
Carries information from DNA to protein synthesis.
Where is mRNA made?
In nucleus.
Where is mRNA exported?
In cytoplasm.
Why is MRNA exported in cytoplasm?
To make proteins.
Where else can mRNA synthesise proteins?
In mitochondria.
Chloroplasts.
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.
What do proteins represent?
The major DNA endpoint information.
How does genetic information generally flow?
In a one-way direction.
Why is DNA encoded?
To make RNA.
Why is RNA coded?
To make polypeptides.
What do polypeptides form?
Proteins.
Why the flow of genetic information has been described as the central dogma of molecular biology?
Because of its universality.
How many sequential processes are essential in all cellular organisms?
2.
Which are the 2 processes essential in organisms?
- Transcription.
2. Translation.
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.
What happens in translation?
mRNA is decoded –> makes polypeptides at ribosomes.
Where are large RNA-protein complexes found?
In cytoplasm.
In mitochondria.
In chloroplasts.
Where is genetic information encoded?
In linear sequence of nucleotides in DNA.
When is genetic information copied?
During transcription.
Why is genetic information copied during transcription?
To specify a linear sequence of nucleotides in RNA product.
What is read in a linear sequence to specify amino acids’ sequence in polypeptide product?
3 nucleotides at a time = codons.
What do RNA viruses have?
An RNA genome.
A gene that makes reverse transcriptase.
What happens in a reverse transcriptase of RNA viruses?
DNA polymerase uses RNA template –> make DNA sequence copy.
What do many DNA sequences in our cells specify?
Reverse transcriptase.
Why do many DNA sequences in our cells have reverse transcriptase?
To allow DNA copies to be made from different RNAs.
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.
What do all proteins have?
A linear polypeptide backbone with carbohydrate, lipid, and small chemical groups added.
What are DNA and RNA strands?
Large polymers.
With very similar structures.
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.
What are the sugars in RNA and DNA?
RNA sugar: ribose.
DNA sugar: deoxyribose.
What is the difference between DNA and RNA sugars?
Lack (DNA)/possessing (RNA) -OH group at 2’-carbon positions.
What does identify the nucleic acid and determine its function?
Sequence of bases.
Of what do the bases of a nucleic acid consist?
Heterocyclic rings: carbon + nitrogen atoms.
What are the 2 structural classes bases are divided into?
- Purines.
2. Pyrimidines.
What do purines have?
2 interlocked rings.
What do pyrimidines have?
A single ring.
What are there in both DNA and RNA?
4 principal base types.
2 purines.
2 pyrimidines.
Which are the common bases in both DNA and RNA?
Adenine.
Cytosine.
Guanine.
Which is the fourth in each of DNA and RNA?
DNA: Thymine.
RNA: Uracil.
What is the difference between thymine and uracil?
Uracil lacks 5-methyl group found in thymine.
To what is each base attached in nucleic acids?
To sugar.
How is each base attached to a sugar in nucleosides?
By an N-glycosidic bond.
What does N-glycosidic bond join in nucleosides?
A nitrogen to carbon 1’ of sugar.
What is a nucleoside?
Sugar attached to a base.
What is the basic repeat unit of a DNA strand?
A nucleoside with a phosphate group attached at 5’ or 3’ carbon of sugar.
How is the nucleoside with a phosphate group attached at 5’ or 3’ carbon of a sugar called?
A nucleotide.
What else does DNA contain?
Minor base.
By what are minor base types produced?
Chemical modification.
By what are proteins composed?
One/more polypeptide chains.
How can polypeptide chains be modified?
BY addition of carbohydrate side chains.
Other chemical groups.
What are polypeptides?
Polymers.
What do polypeptides have?
A linear sequence of repeating units.
How are the repeating units of polypeptides called?
Amino acids.
What happens to amino acids in their electrically neutral form?
Amino group connected by a-carbon atom to carboxyl group.
What does an identifying side chain determine in amino acids?
Their chemical nature.
What does the amino group gain at neutral pH?
A proton.
How does the amino group become once it gains a proton at neutral pH?
Positively charged.
What does the carboxyl group of amino acids lose at neutral pH?
A proton.
How does the carboxyl group of amino acids become once it loses a proton at neutral pH?
Negatively charged.
What does a polypeptide have?
A repeating backbone.
What happen on the repeating backbone of polypeptides?
Amino acids linked by amide groups by peptide bonds.
Into how many groups can the 20 different amino acids be classified?
3 main groups.
What do covalent bonds require to break?
High energy input.
How can noncovalent bonds break?
At physiological temperatures.
When are hydrogen bonds formed?
When H+ interacts with electron atoms: O2/Ni.
Where do ionic interactions occur?
Between charged groups.
Where are ionic interactions weak and when strong?
Weak = in aqueous environments. Strong = in crystals.
Where are ionic bonds important?
In biological function.
Enzyme-substrate recognition.
What do Van der Waals forces show?
Weak attractive bonding interaction.
Why do Van der Walls force have weak bonding?
Due to electrical charges.
What happens when atoms become extremely close?
Knockout each other strongly.
Where can Van der Walls forces be important?
Between surfaces of 2 macromolecules.
What is the cellular environment?
Aqueous.
What is the structure of water?
Complex.
What does the water structure include?
Rapid network.
Noncovalent bonding.
What is the most important force in water molecules?
Hydrogen bond.
What is hydrogen bond?
Weak.
Electrostatic.
Where does hydrogen bond occur?
Between positive hydrogen atoms and negative atoms.
What is a characteristic of charged molecules?
highly soluble in water.
What are DNA and RNA based on the phosphate groups of their nucleotides?
Negatively-charged polyanions.
What can proteins be based on their amino acid composition?
Neutral.
Positive.
Negative.
When are neutral proteins soluble?
If they contain charged/neutral polar amino acids.
Wat are the membrane-bound proteins with many hydrophobic amino acids, in a hydrophobic encironment?
Thermodynamically more stable.
What do noncovalent bonds allow?
Interactions between different molecules.
Why is hydrogen bonding important?
It allows interactions between different nucleic acids.
Facilitates recognition by regulatory RNAs of target sequences in other rRNAs/DNA.
How are neighbouring sugars linked?
By 3’- 5’ phosphodiester bonds.
What happens in 3’- 5’phosphodiester bonds?
Phosphate group links 3’ carbon of one sugar to 5’ carbon of next sugar-phosphate backbone.
What is the genetic material of viruses?
Single-stranded DNA.
How many species does each cellular DNA species have?
2 DNA strands.
How are the 2 DNA strands structured?
As a double helix.
What happens in the double helix?
Strands curve around each other.
How is base pair structured?
Each base on one DNA = non-covalently linked to opposed base on opposite DNA strand.
What does base pairing involve?
Certain purine-pyrimidine combinations only.
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.
Which base pairs are accepted in DNA?
A-T.
G-C.
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.
Which bonds are stronger in the DNA molecule?
The 3 hydrogen bonds between G-C pairs.
How is the base composition of DNA measured?
Amount of A% = amount of T%.
Amount of G% = amount of C%.
Total = 100%.
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.
What is the orientation of each nucleic acid strand?
5’ –> 3’.
In what orientation must 2 strands which form a duplex be?
In an antiparallel arrangement.
What do we mean by ‘antiparallel arrangement of duplex DNA’?
5’ –> 3’ direction of one DNA strand = opposite to its partner’s orientation.
Why are the hydrogen bonds formed in base pairing important?
They form a double helix.
Why are the base-stacking forces important?
They stabilise the helix between adjacent bases.
What are the characteristics of double helix?
Rigid.
Uniform structure
What can double helix undergo?
Local changes.
Alternative base pairing types.
Which base pairs can make the minor groove of double helix narrower?
A-T base pairs.
What is an alternative type of double helix that can be formed?
Z-type DNA double helix.
What can the base pairs in DNA adopt?
Different geometries.
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.
What are the telomeres?
The specialised sequences at the ends of linear chromosomes.
What are the cytokine modifications?
Epigenetic marks important for regulating gene expression.
For how much distance do bases show perfect matching in a double-stranded DNA in humans?
Over 249 million nucleotides.
What do the 2 DNA strands of a duplex exhibit?
Base complementarity.
What do the 2 DNA strands of a duplex have?
Complementary base sequences.
By what is the genetic information encoded?
By the linear sequence of bases in DNA strands.
How are nucleic acids defined?
By their base sequences.
In which direction are base sequences written?
In the 5’–>3’ direction.
What is the 5’ –> 3’ direction about?
The direction of synthesis of new DNA/RNA from a DNA template.
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’.
How can we make a complementary DNA strand: 3’ –> 5’?
By the template strand (given): 5’ –> 3’.
How is DNA replication characterised?
Semi-conservative.
What must happen to each double-stranded DNA before cell divide?
They must be replicated.
Why must each double-stranded DNA be replicated before cells divide?
To generate 2 identifiable double helices, 2 daughter cells.
What must happen first in DNA replication?
The 2 DNA strands of original double helix –> unwound.
How can the 2 DNA strands be unwound?
By a DNA helicase.
What happens to the 2 unwound DNA strands?
Each is used as a template by a DNA polymerase.
What does each template strand make?
A complementary DNA strand.
How are the complementary strands made?
With 4 deoxy nucleoside triphosphates: dNTPS.
What is dNTPS?
A combination of dATP, dCTP, dGTP, and dTTP.
What does the DNA Polymerase do?
Cleaves the dNTP precursors between first and second phosphates.
How is DNA synthesis initiated?
By using an RNA primer and a specialised primase enzyme.
What happens in DNA synthesis?
The new DNA chain grows.
How does the new DNA chain grow?
By adding nucleotides one at a time to the 3’.
How are nucleotides added to make the new DNA strand?
By using a DNA-dependent DNA polymerase and dNTPS.
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.
Of what does the parental duplex consist?
Of 2 complimentary DNA strands.
What does each completed daughter DNA duplex contain?
One of the 2 parental DNA strands + one newly synthesized DNA strand.
To what is each completed daughter DNA duplex identical?
To each other and to the original parental DNA duplex.
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.
How are the specific points, DNA replication is initiated called?
Origins of replication.
What is the overall direction of chain growth for one newly synthesized daughter strand?
5’–>3’.
What is the direction for the lagging strand?
3’ –> 5’.
What do the reactions catalysed by DNA polymerase involve?
Adding dNMP residues to the free 3’ hydroxyl group of the growing DNA strand.
What does the leading strand always have?
A free 3’ hydroxyl group that allows continuous elongation in the same direction as the replication moves.
Why is a DNA helicase needed?
To open up a replication fork.
What does DNA helicase allow?
Synthesis of new daughter DNA strands to begin.
Why is replication discontinuous?
Because lagging strand is synthesized in the opposite direction and is built up in pieces, Okazaki fragments.
What happens to the Okazaki fragments?
They will be stitched together with a DNA ligase.
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.
What will happen to the RNA primers after replication?
Will be removed and replaced by a DNA sequence.
What is the direction of synthesis of the lagging strand?
Opposite to replication fork direction.
What is the difference between RNA polymerases and DNA polymerases?
DNA polymerases need a primer with a free 3’ hydroxyl end to initiate synthesis.
How many RNA primers are needed when synthesizing the leading strand?
Just one.
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.
Where does the machinery for DNA replication rely?
On a variety of proteins and RNA primers.
How many DNA polymerases do mammalian cells have?
20.
What do DNA polymerases in our cells use?
An individual DNA strand as a template for synthesizing a complementary DNA strand.
What do RNA-directed DNA polymerases use in our cells?
RNA templates to make complementary DNA sequences.
How are RNA-directed DNA polymerases called?
Reverse transcriptases.
What do DNA-directed DNA polymerases include?
DNA polymerases delta and epsilon to copy accurately DNA sequences.
What do DNA polymerases do?
Replicate most of the nuclear DNA of our cells.
What does polymerase delta synthesize?
The lagging strand.
What does polymerase epsilon synthesize?
The leading strand.
What do the delta and epsilon enzymes have?
Low error rates.
Why do delta and epsilon polymerases have low error rates?
Because they have an associated 3’ -5’ exonuclease activity responsible for proofreading.
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.
What does initiation of DNA replication and of Okazaki fragments require?
DNA polymerase alpha.
What id the DNA polymerase alpha?
polymerase complex + primase.
What does DNA polymerase alpha lack?
Own proofreading function.
What happens in polymerase alpha?
Errors made in base incorporation are corrected without needing polymerase delta.
What does DNA polymerase gama have?
An intrinsic proofreading exonuclease activity.
What does polymerase gama synthesize?
Mitochondrial DNA.
Where do DNA polymerases function?
Recombination and DNA repair.
Which are the major classes of proteins involved in DNA replication?
- Topoisomerases.
- Helicases.
- Single-strand-DNA binding proteins.
- Primases.
- DNA polymerases.
- DNA ligases.
What do topoisomerases do?
Break a single DNA strand –> release tension –> helix uncoiled form –> DNA unwound.
What do helicases do?
Unwind double helix at replication fork.
What do single-strand-DNA binding proteins do?
Maintain stability of replication fork.
Protect single-stranded DNA from being degraded.
What do primases do?
Attach a primer to single-stranded DNA at replication fork.
What do DNA polymerases do?
Synthesize new DNA strands.
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.
What is RNA normally?
Single-stranded.
What do certain RNA viruses have?
A double-stranded RNA genome.
How can double-stranded RNA be formed by a single-stranded RNA genome?
Transcription of RNA sequences –> make a complementary RNA.
What do RNA molecules need to have?
RNA-RNA base pairing.
What do RNA sequences form when they engage with DNA sequences?
RNA-DNA duplexes.
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.
What is it important in shaping the structure of a single-stranded RNA?
Hydrogen bonding.
Where else is hydrogen bonding important in single-stranded RNA?
Functional, short, double-stranded sequence recognised by specific RNA-binding proteins.
What are the most common type of secondary structure?
Hairpin structures.
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.
How can viruses be classified?
+ viruses.
- viruses.
Where do DNA viruses replicate?
In nucleus.
Where do RNA viruses replicate?
In cytoplasm.
What does RNA replication have higher than DNA replication?
Error rate.
What does the elevated mutation rate allow RNA viruses?
Adapt rapidly to changing environmental conditions.
What are the retroviruses?
RNA viruses.
Where do retroviruses replicate?
In nucleus.
Into what is the single-stranded RNA genome of retroviruses converted?
A single-stranded complementary DNA.
How is the single-stranded RNA genome of retroviruses converted into a single-stranded complementary DNA?
By using a viral reverse transcriptase.
What happens to the complementary DNA?
Converted into a double-stranded DNA.
How is cDNA converted into a double-stranded DNA?
By using a DNA polymerase from the host cell.
What do viral proteins do?
Help instert the double-stranded DNA into the genome of the host cell.
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.
Where is DNA replication initiated?
At origins of replication.
What does DNA replication generate?
Y-shaped replication forks.
What happens in Y-shaped replication forks?
The parental DNA duplex is opened up.
What do the antiparallel parental DNA strands do?
Serve as templates for the synthesis of complementary daughter strands which run in opposite directions.
What is the direction of one newly synthesized daughter, leading strand?
5’ –> 3’.
What is the direction of the other daughter lagging strand?
3’ –> 5’.
What do the reactions catalysed by DNA polymerase involve?
Adding dNMP residues to the free 3’ hydroxyl group of the growing DNA strand.
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.
What does a DNA helicase do?
Opens up a replication fork –> synthesis of new daughter DNA strands begins.
How is replication characterised?
Semi-discontinuous.
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.
How will the Okazaki fragments stich together?
Using DNA ligase.
What are the Okazaki fragments?
100-1000 nucleotides joined by enzyme DNA ligase that make the lagging strand, in opposite direction of replication fork.
How is the leading strand synthesized?
Continuously.
Can DNA polymerases initiate synthesis?
No.
When can DNA polymerases initiate synthesis?
Only when a short oligonucleotide primer with a free 3’ hydroxyl end is provided.
For what are RNA primers needed?
Initiating synthesis.
By what are RNA primers synthesized?
DNA primase.
How many RNA primers are needed in synthesis?
Only one.
What happens in synthesis of Okazaki fragments?
An RNA primer is needed to initiate synthesis of each fragment.
How will the RNA primer be removed?
With a 5’ –> 3’ exonuclease.
By what will the RNA primers replaced after synthesis?
By the corresponding DNA sequence.
On what does the machinery for DNA replication rely?
On proteins.
On RNA primers.
On evolution.
Where is DNA replication more compelx?
In eukaryotes.
How many DNA polymerases do mammalian cells have?
20.
What does each DNA polymerase have?
Special function.
What are most of the DNA polymerases in our cells?
DNA-directed.
What do DNA polymerases do in our cells?
Use an individual DNA strand as a template –> synthesise a complementary DNA strand.
What other polymerases do we have in our cells?
RNA-directed DNA polymerases.
How are RNA-directed DNA polymerases named?
Reverse transcriptases.
What do RNA-directed DNA polymerases do?
Use RNA templates –> make complementary DNA sequences.
How many structures does a double helix have?
3.
What are the 3 structures of the double helixes?
A-form.
B-form.
Z-form.
What is the difference between the A-form and the B-form?
A-form is shorter and wider.
Has a deep, narrow major groove.
When does A-DNA structure exist?
Only under non-physiological conditions.
Where .can G-U base pairing occur?
In short regions of double-stranded RNA in the RNA strand.
Is the G-U base pairing stable?
No.
Does the G-U base pairing distort the RNA-RNA helix?
No.
What can DNA have?
Cell-type specific function.
Why can DNA have cell-type specific functions?
Because it contains sequences used to make RNA and polypeptides which differ from cell to cell.
What are genes?
Discrete DNA segments.
Spaced at irregular intervals in the DNA strand.
Serve as templates.
Why do genes serve as tmplates?
To make complementary RNA sequences in transcription.
What must the initial primary RNA transcript undergo?
Maturation steps.
Why must the primary RNA transcript undergo maturation steps?
To make the mature functional mRNA.
What does the mature mRNA do?
Serves as template –> makes a polypeptide.
What are the gene products needed for?
Vital cell processes = DNA Replication, protein synthesis.
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.
What are the DNA compositions of the different cell types in an organism?
Identical.
Why is there variation in cells in an organism?
Because there are gene expression differences in transcription.
Different genes are transcribed.
On what does gene expression depend?
On cells’ needs.
What does transcription mean?
RNA –> synthesized
Using DNA-directed RNA polymerases.
What happens in transcription?
DNA strands = templates for RNA synthesis.
Where is RNA synthesized in eukaryotic cells?
In nucleus.
What is transcribed in eukaryotic cells?
Nuclear genes.
Where is a small amount of genes transcribed.
In mitochondria.
Chloroplasts.
How are genes transcribed in mitochondria and chloroplasts?
DNA in organelles –> transcribed.
Where are chloroplasts found?
In plant cells.
What happens to the DNA during transcription?
DNA helix –> unwound locally –> separated DNA strand –> RNA polymerase comes –> makes a complementary RNA sequence.
Where is RNA polymerase and DNA polymerase used?
RNA Polymerase: Transcription.
DNA Polymerase: DNA Replication.
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.
How is the nontemplate called?
Sense strand.
How is the template strand called?
Antisense strand.
Which DNA strand is used by the RNA polymerase as a template to synthesize a complementary RNA strand?
The template strand.
From what is the RNA strand synthesized?
Ribonucleoside triphosphate precursors. (rNTPs).
What does the polymerase do to synthesize RNA?
Opens rNTPs –> gives Ribonucleoside monophosphates (rNMPs).
How are the rNMPs inserted?
One nucleotide as a time.
How are the rNMPs inserted?
Join the 3’OH of previous nucleotide based on base pairing rules.
On what is RNA transcription based?
Base Pairing rules.
On which DNA strand will the RNA strand be complementary and on which identical?
Complementary to the template strand.
Identical to the sense strand.
From which 4 precursors does RNA Polymerase synthesize RNA?
ATP, CTP, GTP, UTP.
What does elongation involve?
Addition of appropriate ribonucleotide monophosphate: AMP, CMP, GMP, UMP to 3’OH end of growing RNA strand.
How can transcription run ffectively?
Various proteins bind DNA sequence –> guide RNA Polymerase.
What is also important to be added in transcription?
DNA elements.
How many classes of DNA-dependent RNA polymerase occur in eukaryotic cells?
4.
Where are the 3 DNA-dependent RNA polymerase classes used?
Transcribing nuclear genes.
Where is the last DNA-dependent RNA polymerase used?
Transcribing mitochondiral DNA.
By what is the mitochondrial RNA polymerase encoded?
Nuclear gene.
How is the mitochondrial DNA transcribed?
Nuclear gene –> encoded –> mRNA –> cytoplasm –> ribosomes –> translation –> mitochondria.
What is the difference between DNA Polymerases and RNA polymerases?
RNA polymerases do not need primer to initiate RNA synthesis.
What do RNA polymerases need to start transcription process?
Protein regulators = transcription factors .
What do transcription factors do?
Bind to certain DNA sequences with gene –> activate transcription process.
To what can a transcription factor bind?
To a promoter.
What is a promoter?
A collection of closely spaced short DNA sequence elements in a gene neighbourhood.
What do transcription factors activate once they bind to a promoter?
The RNA Polymerase.
Where are promoters and primase used?
Promoter: RNA Polymerase –> transcription.
Primer: DNA Polymerase –> DNA replication.
What are the transcription factors?
Trans-acting.
Why are the transcription factors trans-acting?
Because they are produced be remote genes –> migrate –> to sites of action.
What are the promoter sequences?
Cis-acting?
Why are the promoters cis-acting?
Because the are located on the same DNA molecule where they regulate the genes.
For what is the RNA polymerase 2 responsible?
Transcribing all protein coding genes in nucleus + important genes encoding noncoding RNAs.
Where does RNA polymerase 2 rely?
Transcription factors.
Tissue specific
Cell specific factors
Where does RNA Polymerase 1 occur?
Nucleolus.
What does RNA Polymerase 1 synthesize?
Cytoplasmic ribosomal RNAs.
Where does RNA polymerase occur?
Nucleoplasm.
What does RNA Polymerase 2 synthesize?
mRNAs nuclear genes + noncoding RNAs, snRNAs, miRNAs, IncRNAs, snoRNAs.
Where does RNA Polymerase 3 occur?
Nucleoplasm.
What does RNA polymerase 3 synthesize?
Small noncoding RNAs, ribosomal RNA, cytosolic tRNAs.
Where does RNA Polymerase mt occur?
Mitochondria.
What does RNA polymerase mt synthesize?
RNAs from mitochondrial DNA.
