Exam Review Flashcards
What did Frederick Griffith contribute to our understanding of DNA
Performed experiments with Smooth (S) and Rough (R) bacteria. Injecting mice with killed S and live R killed mice and they found live S and live R.
Lead to the transforming principle
What is the transforming principle
Ability of a substance to change the genetic characteristics of a cell
How did Oswald Avery contribute to our understanding of DNA
Found the component responsible for the transformation principle
Combined the live R and dead S with 1) proteases to kill protein 2) ribonucleases and 3) DNA-ase to breakdown DNA
combination 1 and 2 produced living S, using DNA-ase stopped the formation of live S
How did Hershey and Chase contribute to our understanding of DNA
Determined what substance hereditary information was made of using the Waring Blender Experiment
Used radioactive phosphorus to identify DNA and radioactive sulphur to identify protein.
After bacteriophages injected into bacteria, used centrifuge to separate phage ghosts (only protein) and bacteria (labeled with DNA)
Purines
A and G
2 ring structure
Pyrimadines
T and C
1 ring structure
How does DNA replication occur
Semi-conservatively
Steps to initiation of DNA replication
initiation complex binds to origin of replication
DNA helicase catalyzes unwinding
SSB proteins keep the strands separated
Steps to elongation of DNA replication
DNA primase makes an RNA primer
DNA polymerase III extends DNA from this primer in the 3’ direction
RNA primers are added as replication bubble opens
DNA polymerase I replaces RNA primers with DNA
DNA ligase seals the 3’ OH and 5’ PO4 nicks by catalyzing phosphodiester bonds
Stop Codons
UAA, UAG, UGA
What did Crick and Benner contribute to our understanding of the amino acid reading frame
Evidence for triplet code
Mutations occuring in multiples of 3’s provide proteins that still function as long as mutations are close together
Start Codon
AUG
Rho-dependent vs Rho-independent transcription termination
dependent = no terminator on RNA, rho protein causes destabilization of polymerase independent = terminator on RNA, base pairing causes a secondary structure of a hairpin to form
True or false:
Prokaryotes use sigma factor to form a holoenzyme with RNA polymerase to attach to the promoter region
True
Intragenic suppression
restoration of gene function occurs with one mutation cancelling out another one
Initiation of translation in prokayotes
small ribosomal subunit binds to shine-dalgarno sequence
tRNA carrying f-Met binds to start codon
large ribosomal subunit binds placing tRNA in P site
Initiation of translation in eukaryotes
small ribosomal subunit binds to 5’ methylated cap
Proceeds to the first start codon (AUG) downstream
Making a clone
Put a fragment of DNA into a vector
Treat both plasmid and fragment with the same restriction enzyme
To determine if the cells have taken up the plasmid test with ampicillin - to see if resistant - and lactose - to see if stays white or turns blue
genomic library
DNA clone collection that contains theoretically every DNA fragment in a genome
contains ALL sequences
not organism dependent
mostly used for prokaryotes or gene sequencing
cDNA
Complimentary DNA
DNA sequences that have been copied from mRNA transcripts
Contains only exon sequences
cell type dependent
mostly used for eukaryotes or expressed sequences
Whose experiment lead to the understanding of semi-conservative DNA replication
Meselson and Stahl
