1B: Transmission of genetic information from the gene to the protein Flashcards
Nucleotides
Monomers of nucleic acids, consists of sugar, nitrogenous base and phosphate group
Types of Nucleotides
Thymine, Adenine, Guanine, Uracil
Structure of Nucleotides
Phosphorus is linked at the 5 carbon of the sugar; Nitrogenous Base is linked to the 1 carbon of the sugar
Pyrimidines
Single ring; Cytosine, Uracil, Thymine
Purines
Two rings; Adenine, Guanine
Nucleoside
Sugar + Nitrogenous Base
Types of Nucleosides
Cytidine, Uridine, Adenosine
DNA
Deoxyribonucleic Acid
Double Helix
2 single strands of DNA wound around each other held together by hydrogen bonds
Watson-Crick Model
Two linear strands running antiparallel and twisted in a right-handed spiral; bases are located inside of the helix
Base Pairing Specificity
Nucleobases are connected via hydrogen bonds:
A2T
C3G
DNA with more G-C are more stable
Function of DNA in transmission of Genetic Information
Complementary base pairing property allows for DNA replication and transmission of genetic information
Central Dogma
DNA -> RNA -> Protein
Denaturation of DNA
dsDNA comes apart due to heating or a change in pH
Annealing of DNA
ssDNA joins again due to complementary nucleotide sequences and random molecular motion
Hybridization of DNA
Denatures two different DNA sequences then uses ssDNA from each to anneal to dsdna
Process of PCR
Denature -> Anneal -> Extend
Mechanism of Replication
- Separation of Strands
2. Coupling of Free Nucleic Acids
Enzymes of Replication
- DNA Gyrase
- Helicase
- SSB - Primase
- DNA Pol III
- DNA Pol I
- DNA Ligase
Helicase
Unwinds double helix of DNA
DNA Pol III
Binds one strand of DNA from an RNA primer, moves 3’ to 5’ producing a leading strand
Primase
Produces RNA primers at the 5’ end, allowing for the synthesis of Okazaki fragments
Okazaki Fragments
Short discontinued fragments of replication products on the lagging strand
DNA Pol I
Removes RNA primers by the 5’ end to 3’ end
DNA Ligase
Seals the spaces in the strand between the Okazaki Fragments
Single-Strand Binding Protein
Responsible for keeping the DNA unwound after helicase unwinds the helix
DNA Gyrase
Uncoils DNA ahead of the replication fork
Semi-conservative nature of replication
Each DNA helix contains one parent strand and one new strand; older DNA has more methyl groups added so its always possible to determine which strand is older
Origin of Replication
Point at which replication begins; multiple points in eukaryotes and singular in prokaryotes
Telomerase
Replicates the end of DNA molecules which consist of telomeres that help keep genetic information and prevent it from being lost during replication
Repair during Replication
DNA Pol has proofreading activity (3’->5’ exonuclease) which replaces incorrect nucleotides
DNA Pol I has 5’->3’ exonuclease activity which allows for removal of incorrect nucleotides
Repair of Mutation
Mismatch Base-Excision Nucleotide-Excision Nick Translation SOS Response
Mismatch Repair
Enzymes recognize incorrectly paired bases and cuts out the stretch of DNA containing the mismatch; utilizes methylations to determine old from new strand
Base-Excision Repair
A single base is removed and replaced using DNA Pol and Ligase
Nucleotide-Excision Repair
Damaged nucleotide gets cut out and replaced (due to thymine dimers)
Nick Translation
RNA primers are replaced with DNA through 5’ to 3’ activity
SOS Response
When there is too much DNA for normal repair; the DNA Pol replicates over the damaged area as if it were normal
Triplet Code (Codon)
Sequence of nucleotides of mRNA that codes for amino acids; 3 nucleotides = single amino acid
Anticodon
3 bases at the end of tRNA (transfer anticodon) that correspond to the nucleotide triplet in mrNA during translation
Degenerate Code
Multiple 3 codon combinations code for the same amino acid (20 total); more than one codon codes for a given amino acid
Wobble Pairing
When two nucleotides in RNA molecules do not follow Watson-Crick base pairing rules
Types of Wobble Base Pairs
G-U I-U I-A I-C I=hypoxanthine
Missense Mutations
A new nucleotide changes the codon to produce a changed amino acid in protein
Nonsense Mutations
A new nucleotide changes the codon to a stop codon that prematurely truncates a protein
Initiation Codon
AUG (methionine); starts the translation process
Prokaryotes = Shine-Delgarno Sequence
Eukaryotes = Kozak Sequence
Termination Codon
End translation of the mRNA strand
UAA
UAG
UGA
mRNA
Carries genetic information (in the form of codons) that corresponds to amino acids for protein synthesis
5’ terminal is capped by a 7-methyl guanosine triphosphate cap; 3’ end is added poly-A tail
tRNA
In the cytoplasm, directs translation of mRNA into proteins; contain anticodon
rRNA
Necessary for ribosome assembly, plays a role in mRNA binding to ribosomes and in translation, contains active site for catalysis (peptide bond formation)
Mechanism of Transcription
[Eukaryotes = Nucleus]
[Prokaryotes = Cytoplasm]
Initiation -> Elongation -> Termination
Initiation
RNA Pol binds to the promoter region of DNA
Elongation
Transcription factors unwind the DNA strand and allow RNA Pol to transcribe a strand of DNA into a strand of mRNA; C3G, A2U
Termination
RNA Pol reaches a terminator sequence and then releases the mRNA polymer and detaches from the DNA
Eukaryotic Structure
5’ UTR
Coding Sequence
3’ UTR
Coding Sequence
Where translation begins and ends; contains amino acid sequences for protein synthesis during translation
3’ UTR
Contains crucial information for mRNA stability
Processing in Eukaryotes
- Cap Addition
- Polyadenylation
- Splicing
Cap Addition
Addition of a 5’ methyl guanosine cap that occurs during transcription; prevent chain degradation
Polyadenylation
A poly-A tail is added to the 3’ end; enhances the stability of mRNA and regulates transport to cytoplasmic compartment
Splicing
Removes introns
Introns
Not expressed in proteins
Exons
Encoding sequences and they are reserved
Ribozymes
Ribonucleic Acid Enzymes; catalyzes biochemical reactions, join amino acids together and form protein chains; play a role in RNA splicing, viral replication and RNA biosynthesis
Spliceosomes
Splicing machines that remove and cut introns from pre-mRNA
snRNA
Small nuclear RNA, couples with snRNPs that 5’ and 3’ splice sites of introns
snRNPs
Combine of snRNA and protein factors that are essential in intron removal
Eukaryotic Ribosome
40S + 60S; 80S
Prokaryotic Ribosome
30S + 40S; 70S
General Ribosome Structure
mRNA binding site (small subunit); E site, P site and A site (large subunit)