DNA Function

How large is the human genome

6 billion bp

What binds to origins of replication to start DNA replication

initiator proteins

What does helicase do

unwinds DNA breaking H-bonds at the replication fork

What do origin binding proteins do 

open DNA helix at origin of replication 

What does topoisomerase do

prevents supercoiling by creating microcuts and fixing them once the tention has passed

Why are nucleotides only able to be added at the 3’ end

due to the free -OH

How does energy from nucleotides create energy to build DNA

2 of the 3 phosphates split off to form pyrophosphate and then 2x Pi generating energy 

What does DNA Primase do

synthesizes DNA primers for the lagging strand

How accurate is DNA Polymerase

1:107 before proofreading

What happens if an error is made by DNA Polymerase

phosphodiester bonds are cleaved

What does DNA Polymerase III do

elongation

What does DNA Polymerase I do

replacement of RNA primer with nucleotides

What does DNA Ligase do

joints ekazaki fragments

What are the stop codons 

UAA, UAG, UGA

When is the 5’ cap added

first 20-30 nucleotides

Why is the 5’ cap essential

required to bind to ribosome

What direction do the tRNA and mRNA run in

antiparalell

What is the name for a ‘loaded’ tRNA

aminoacetyl-tRNA

What are the roles of rRNA

structural and catalytic

What are the 3 sites of the ribosome for tRNA binding

A,P,E

Where does initation occur

the small ribosomal subunit

What is the start codon

AUG, codes for Met

What happens when the start codon is reached 

initiation factors disassociate and large ribosomal subunit binds to create whole ribosome

Where does elongation occur

The P site

What is the stop codon recognized by

release factors

Where does release factor bind 

A site