DNA/RNA Flashcards
Structure of a nucleotide (3 parts)
Phosphate group on 5’ carbon, Pentose sugar with OH on 3’carbon, Nitrogen base
DNA Polymerase can only build DNA from the __ end.
3’ End. (With -OH group)
DNA strands are connected by…
Hydrogen bonds
How many bonds are between each base pair?
A-T have 2. G-C have 3.
When does DNA replicate?
Just before cell division
Where does DNA replicate?
Nucleus
Where can you find an origin of replication site?
At a place with a lot of A-T base pairs
Replication proteins: Helicase
Unwinds DNA by breaking H bonds.
Replication proteins: Single strand binding proteins
Prevents re-pairing of DNA strands.
Replication proteins: Topoisomerase
prevents “super twisting”
Replication proteins: DNA Polymerase
Makes DNA starting on 3’ side
Replication proteins: Primase
makes RNA primer
Replication proteins: DNA Ligase
Makes phosphodiester bond “seals nick”
Genome
Complete set of genetic information for an organism
Telomeres
ends of chromosomes, stretches of repeated bases. prevent lose of genes by buffering loss of chromosome length.
Somatic Cells
General body cells
Hayflick Limit
40 divisions
Which kinds of cells can pass the hay flick limit?
Zygotes and stem cells
Telomerase
exists in zygotes and stem cells to extend length of telomeres so that chromosomes do not shorten.
Repair Systems for DNA (2 General)
DNA Polymerase has a proofreading system. Also some mismatch repair systems.
Excision Repair
Nuclease Enzyme cuts DNA, DNA Pol fills gap, Ligase finishes
Nuclease Enzyme
cuts DNA during excision repair
Chromosome cell structure
DNA wraps around histones->8 histone nucleosome complex->nucleosomes wrapped into 30 nm fiber->fibers wrapped into looped domains (300nm) ->loops form metaphase chromosomes
Gene Expression
Process from DNA to building of protein
Gene Expression (Specifics)
Transcription->Pre mRNA->RNA Processing=mRNA ->Translation at ribosome to make protein.
Transcription Process (3 general steps)
Initiation, Elongation, Termination
Transcription: Initiation stage
RNA Polymerase binds to promoter, unwinds DNA and reads bottom strand, builds in 5’-3’ direction
Transcription: Elongation stage
RNA Pol continues down DNA strand making RNA strand longer
Transcription: Termination stage
signals end of gene
TATA box
25 base pair downstream that indicates where RNA Pol must start
Transcription Factors (object)
Binds to TATA box before RNA Pol comes in
Transcription Initiation Complex
Combo of Transcription Factors and RNA Pol.
Pre mRNA -> mRNA process (Step 1)
Add 5’ cap and Poly A tail to pre mRNA
Pre mRNA -> mRNA process (Step 2)
Remove introns via RNA Splicing
Introns
Non expressed portions of gene
Exons
Expressed section of gene
RNA Splicing
brings exons together
snRNA’s
involved in splicing out introns
SNURP
small nuclear ribo proteins (snRNA’s and protein complex)
Spliceosome
Complex of slurps that splice exons together
Alternative RNA Splicing
Each gene can create more than one protein depending on which exons are cut out
Sections of RNA
untranslated region, start codon, codons, stop codon
Redundancy
a single amino acid can have multiple three letter codons
Sites on a tRNA
amino acid attachment site, and anticodon part to complement mRNA
Aminoacyl tRNA Synthetases
connect amino acids to tRNA’s.
Ribosomes
workbench of translation, made of ribonucleoprotein complexes
Ribonucleoprotein Complex
combo of rRNA and proteins
Formation of an Ribosome
Put together in nucleolus, 2 subunits, large and small.
4 Binding Sites of a Ribosome
mRNA binding site, A, P, and E sites
“A” Binding site of a Ribosome
tRNA with an amino acid sits here and waits to be connected to the mRNA
“P” Binding site of a Ribosome
tRNA binds with the mRNA peptide
“E”Binding site of a Ribosome
tRNA exits
Translation: Initiation Stage (3 steps)
- ) mRNA sits in ribosomal small subunit with AUG in P site
- ) Anti codon of tRNA initiator binds to start codon
- ) Large ribosomal subunit binds ontop
Translation: Elongation Stage (4 steps)
- ) Codon Recognition
- ) Peptide bond formation
- ) Translocation
- ) uncharged tRNA leaves through E site
Translation Elongation Stage: Codon Recognition
Anticodon of next charged tRNA binds to A site
Translation Elongation Stage: Peptide Bond Formation
tRNA start bond broken (met) Met forms peptide bond with next amino acid
Translation Elongation Stage: Translocation
Ribosome moves down mRNA and A site become vacant again
Translation: Termination Stage
Ribosome reaches stop codon and in comes the “Release Factor Protein”, which makes the complex decouple
Release Factor Protein
Comes into a ribosome during termination stage to decouple the entire Ribonucleoprotein Complex
Post Translational Localization
Proteins brought to their destination AFTER translation process
Co-Translational Localization
Signal peptide for ER causes a “Signal Recognition Particle” to bind to signal peptide and halt translation until complex reaches ER, then resumes again.
Point Mutations: 2 Types
Base Substitution and Deletion/Insertion
Types of Base Substitutions
Silent, Missense, and Nonsense Mutations
Point Mutations: Base Subs: Silent
a single base pair is substituted, however it still codes to the same amino acid
Point Mutations: Base Subs: Missense
a single base pair is substituted, however this causes a different amino acid to be put here
Point Mutations: Base Subs: Nonsense
a single base pair is substituted, and this causes a stop codon which causes protein truncation
What system allows protein destruction?
Ubiquitin-Proteosome System
Ubiquitin
a tag that is put on proteins, signaling them to be destroyed
Ubiquitin Protein Ligase
Protein that puts the ubiquitin tag on proteins
Proteosome
chops up ubiquitinated proteins
