Biochemistry - Gene Regulation of Protein Synthesis Flashcards
What does total DNA in each cell consist of?
The entire HUMAN GENOME.
What is GENETIC INFORMATION?
The information (instructions) to make up a whole organism.
Where is the information to make up an organism stored?
NUCLEOTIDE SEQUENCE of the GENOME
The DNA sequence determines the ………. .
SEQUENCE of AMINO ACIDS
What is the name of the process which produces RNA from DNA?
TRANSCRIPTION
nucleotide to nucleotide
What is the name of the process which produces PROTEIN from RNA?
TRANSLATION
nucleotide to amino acid
What is the sugar found in RNA?
RIBOSE
What is the sugar found in DNA?
DEOXYRIBOSE
In what way are the carbon atoms numbered within a nucleotide?
1’ 2’ 3’ 4’ 5’
where ‘ means prime
What is a NUCLEOTIDE?
BASE + SUGAR + PHOSPHATE GROUP(S)
What is a NUCLEOSIDE?
BASE + SUGAR
What are the four bases in DNA?
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
What are the four bases in RNA?
Adenine (A)
Guanine (G)
Cytosine (C)
Uracyl (U)
What group is found on the 3’ Carbon of a Deoxyribose sugar?
HYDROGEN group
What group is found on the 3’ Carbon of a Ribose sugar?
HYDROXYL (OH) group
What size are the Purines?
LARGE
(two)
SMALL NAME, LARGE STRUCTURE
What size are the Pyramidines?
SMALL
(one)
LARGE NAME, SMALL STRUCTURE
What bases belong to the Purines?
Adenine (A)
Thymine (T)
What bases belong to the Pyramidines?
Guanine (G)
Cytosine (C)
Uracil (U)
What are the DNA Building Blocks?
dATP
dTTP
dGTP
dCTP
What are the RNA Building Blocks?
ATP GTP UTP CTP (no deoxy (d) as they have ribose sugar, not deoxyribose)
NOMENCULTURE (base -> nucleoside)
Adenine -> Cytosine -> Guanine -> Thymine -> Uracil ->
(base -> nucleoside)
Adenosine Cytidine Guanosine Thymidine Uridine
What bond is formed between the 3’ OH Group and the 5’ Triphosphate Group?
PHOSPHODIESTER BOND
Which direction do the two strands run in DNA?
Strand 1: 5’ to 3’
Strand 2: 3’ to 5’
What is the name given to the direction in which both strands run in DNA?
ANTI-PARALLEL
Bases are held together by what type of bonding?
HYDROGEN BONDS
What are the base pairings in DNA?
A -> T
G -> C
What are the base pairings in RNA?
A -> U
G -> C
What is the name of the DNA Backbone?
SUGAR-PHOSPHATE BACKBONE
What name describes the type of replication DNA undergoes?
SEMI-CONSERVATIVE
What MUST take place before cell division?
DNA Replication
Why must DNA replication take place before cell division?
To ensure daughter cells have a complete chromosome complement.
Which enzyme catalyses DNA replication?
DNA POLYMERASE
What are the THREE characteristics of DNA Polymersase?
(1) Can only add nucleotides to existing nucleotides
(2) Cannot start DNA replication by itself
(3) Requires RNA primer to start replication
What genome has ORIGINS of REPLICATION?
-o—o—o—o—o-
EUKATYOTIC GENOMES
Where does DNA replication start along the DNA strand?
Starts simultaneously at several points along the strand.
What is the direction of DNA replication?
DNA replication is BIDIRECTIONAL.
What end of the DNA strand can nucleotides be added to?
3’ END ONLY!!!
The fact that nucleotides can only be added to the 3’ end of a growing strand is fine for what strand but a problem for the other?
Fine - Leading Strand
Problem - Lagging Strand
What is the difference between the Leading and Lagging strands in DNA?
Leading Strand - runs in 5’ to 3’ direction meaning DNA polymerase can add nucleotides without problems.
Lagging Strand - runs in a 3’ to 5’ direction causing a problem for DNA polymerase which can only add to the 3’ end of a growing DNA strand.
What is the function of the enzyme Helicase?
Helicase causes DNA to UNWIND and UN-ZIP.
What are the six stages involved in DNA replication?
(1) Helicase unwinds DNA.
(2) Helicase unzips DNA to Y-shaped replication fork.
(3) DNA polymerase adds complementary nucleotides to the 3’ end of Leading Strand without problems.
(4) Lagging strand must be replicated in fragments.
(5) Okizaki fragment tail created and glued by Ligase.
(6) RNA primers replaced with DNA polymerase as they degrade.
What is a PHOSPHODIESTER BOND?
A bond that forms on the 3’ OH Group and 5’ Triphosphate Group?
What enzyme catalyses RNA Primer synthesis?
PRIMASE
How can mutations be created?
By incorporating the WRONG NUCLEOTIDE.
What activity does DNA polymerase have?
3’ to 5’ EXONUCLEASE ACTIVITY
What does Exonuclease Activity do?
Exonuclease Activity is able to detect mistakes in the DNA sequence and correct them.
Further repair systems exist.
What are the three characteristics of RNA?
(1) Single-stranded
(2) U instead of T
(3) Ribose Sugar (OH on 3’C)
What are the three main classes of RNA?
rRNA
mRNA
tRNA
What is rRNA?
rRNA + PROTEINS -> RIBOSOMES
What is mRNA?
mRNA carries genetic information to Ribosomes for Protein Synthesis.
What is tRNA?
Carries AMINO ACIDS to Ribosomes to get incorporated into Polypeptide chains.
Which types of RNA is most stable?
tRNA and rRNA
What % of RNA are there in cells?
80% rRNA
15% tRNA
5% mRNA
Most of r/t as most stable.
What codes does tRNA have to adapt between?
NUCLEIC and AMINO ACID codes.
How many nucleotides make up an ANTI-CODON?
THREE.
What is attached to the 3’ end of tRNA molecule?
AMINO ACID.
Is tRNA 2D or 3D?
Strictly 3D Structure.
What shape does tRNA take after being flattened out?
FOUR LEAF CLOVER.
How many types of RNA Polymerase do Prokaryotic cells have?
ONE.
How many types of RNA Polymerase do Eukaryotic cells have?
THREE.
How many template DNA strands are used to copy nucleotide sequence into RNA?
ONE.
What are the four steps of TRANSCRIPTION?
(1) RNA Polymerase binging
(2) DNA Chain separation
(3) Transcription Initiation
(4) Elongation
What do promoters on DNA require?
TRANSCRIPTION FACTORS.
What is DNA Chain separation?
What does it allow?
- DNA unwinds locally
- Access available to nucleotide sequence
What is Transcription Initiation?
When the FIRST nucleotide for growing RNA strand is selected.
Describe Elongation
Further nucleotides are added as growing RNA strand lengthens.
At what nucleotide does Transcription start?
+1
What specific promoter is used?
RNA Pol II
How many nucleotides before the Transcriptional start is the TATA box present?
25 nucleotides.
What nucleotides is the transcriptional start?
-25
What is TBP?
Tata Box Binding Protein
What does the TBP recognise?
TATA Box
What additional requirements does transcription require?
Additional Transcription Factors
What two types of Ribosome exist?
Free Ribosomes
Bound Ribosomes
Where are Free Ribosomes found?
CYTOSOL.
Where are Bound Ribosomes found?
rER
Rough Endoplasmic Reticulum
Free Ribosomes make proteins for…
Cytosol
Nucleus
Mitochondria
Bound ribosomes make proteins for…
Plasma Membrane
ER
Golgi Apparatus
Secretion
Free Ribosomes are translocated…
POST-TRANSLATIONALLY
Bound Ribosomes are translocated…
CO-TRANSLATIONALLY
What is Glycolisation?
The addition and processing of CARBOHYDRATES in the ER and the Golgi
What are the main types of POST-TRANSLATIONAL MODIFICATIONS?
- folding of di-sulfide bonds in ER
- folding and assembly multisubunit proteins in ER
- specific proteolytic cleavage in ER, Golgi and secretory vesicles
I-CELL DISEASE
I-Y
- inherited recessive disorder of protein targetting
- lysosome proteins not properly sorted in Golgi
- secreted from cell
- clogged lysosomes (cannot digest material)
- death before age 8
What three things happen when protein is finished?
(1) Targeting
(2) Modification
(3) Degradation
Explain Targeting…
- moving a protein to its FINAL DESTINATION
- variable locations
(target, location, destination)
What does Targeting depend on?
Targeting depends on the presence of SPECIFIC AMINO ACID SEQUENCES within the protein itself
What is Modification?
ADDITION of FURTHER GROUPS (chemical)
Explain Degradation…
The REMOVAL of damaged or unwanted proteins.
LARGE MUTATIONS
- deletion
- duplication
- inversion
- translocation
POINT MUTATION
Change in a SINGLE base in DNA
MISSENSE MUTATION
Change in AMINO ACID SEQUENCE
Alters PROTEIN FUNCTION
Example of Missense Mutation
HAEMOGLOBIN
SICKLE CELL ANAEMIA
NONSENSE MUTATION
x3
New TERMINATION CODON
DNA sequence ends prematurely.
SHORTER protein produced.
SILENT MUTATION
NO change in amino acid sequence.
No effect on protein function.
Why does a Silent Mutation cause no harm?
Due to the DEGENERACY of GENETIC CODE.
FRAMESHIFT MUTATION
ADDITION/DELETION of single base or two.
Changes reading frame of protein translation.
Frame shifts - amino acids altered.
What is the POLYSOME?
Many, many ribosomes joined together.
What happens in Transcription Elongation?
Transcription bubble moves in ONE direction along DNA strand.
How does the DNA unwind?
DNA unwound in front of Polymerase and rewound behind it.
What direction is RNA synthesised in?
5’ -> 3’
The new RNA sequence is … to the template DNA sequence.
COMPLEMENTARY.
The new RNA sequence is … to the CODING strand.
IDENTICAL
except U instead of T
How does Transcription Termination take place?
(1) Stem-loop structure formed
(2) UUUUUU sequence
(3) Specific enzyme CLEAVES RNA
