| Question |
Answer |
| replication |
DNA Synthesis |
| Transcription |
RNA synthesis |
| Translation |
protein synthesis |
| When in the cell cycle does DNA replication occur? |
S phase |
| Requirements for DNA replication |
DNA Polymerase
Mg +2
Template
dNTP
Primer |
| Direction of DNA replication |
5' to 3' |
| Complimentary characteristic of DNA replication |
for each A of the template strand, a T is added to teh new strand, and for each G a C is added |
| DNA Polymerase |
enzymes that replicate DNA by catalyzing nucleotide polymerization |
| DNA Replication Proofreading |
3'-5' exonuclease activity excises mixmatches |
| Magnesium |
it is a cofactor required for replication |
| De Nova Strand |
New DNA strand |
| Primer |
free 3' OH on a previously existing strand
A strand with a 3' OH is often reffered to as a primer |
| Bidirectional |
replication in both directions from central origins of replication |
| discontinuous |
lagging strand replicated in short stretches
Okazaki fragments |
| Proofreading |
3' to 5' exonuclease activity that double checks for mistakes |
| dNTPs |
Deoxyribonucleotides
Building blocks of DNA
All four are required for replication |
| complimentary |
Every A is paired with a T and every G with a C
Matching, mirror image sequences are called complimentary sequences |
| How many charges do A and T have? |
Two specific charges |
| How many charges do G and C have? |
Three |
| Semiconservative |
One strand of a daughter chromosome is newly synthesized, the other template strand is inherited intact from teh parental chromosome |
| Overview of DNA Replication |
Initiation
Extension |
| What is the ori? |
Origins of replication
sequences where DNA replication begins.
|
| What is a replicon? |
Region of a eukaryotic chromosome that is replicated as a unit, from one central ori. |
| Where does replication begin? |
At teh ori in teh center of a replicon and extends. |
| How does replication move from the replicon? |
Extends in both directions until it reaches the end of an adjacent replicon |
| What is a helicase |
An enzyme that unwinds DNA
One of the first factors to bind to an ori |
| What are single stranded Binding Proteins? |
SSB
Factors that stabilize single stranded DNA by preventing it from winding back into a double helix. |
| What is a DNA Replication Apparatus? |
a cluster of factors that assemble around helicase to replicate DNA. |
| What are the most important factors of DNA replication apparatus? |
helicase
DNA Polymerase
Pol alpha
Beta clamp
primase |
| Beta clamp |
Ring like protein that wraps aroudn DNA to stabilize the association of teh replication apparatus
Required for Pol processivity
Allows for greater extension |
| Leading Strand Replication |
One strand is continuously synthesized in teh normal 5' - 3' direction |
| DNA Polymerase |
enzyme that replicates the leading strand.
It reads the template one base at a time incorporating complementary nucleotides, ligating their 5' phosphate to the 3' OH of the growing leading strand |
| Pol |
DNA Polymerase |
| Discontinuous Replication of the Lagging Strand |
Other strand is replicated discontinuously with okazaki fragments because the overall direction of lagging strand synthesis is in the opposite direction |
| Primase |
enzyme binds the unwound lagging strand template and transcribes a short stretch of RNA.
Is a primer, providing 3' OH group required by Pol alpha |
| DNA polymerase alpha |
Pol alpha
This enzyme uses the RNA primer to synthesize an okazaki fragment |
| How many Okazaki fragments does Pol alpha synthesize? |
one |
| How long does Pol alpha replicate the okazaki fragment? |
until it reaches the primer at the end of the previous fragment. |
| What happens to the primase when the lagging strand is released? |
Primase makes the next primer at th eend of the new single stranded region and the process is repeated |
| What is a consequence of unwinding by helicase? |
Supercoiling increases |
| What do Topoisomerase do? |
restores the DNA to the proper level of supercoiling |
| How is RNA primers removed from the lagging strand? |
RNAse
DNA polymerase beta
DNA Ligase |
| RNAase |
This enzyme digests any RNA |
| DNA Polymerase beta |
This polymerase fills in gaps in DNA.
It fills in the gaps left after the RNA primers are removed.
Leaves nicks in teh DNA |
| DNA ligase |
Binds any free 3' hydroxyls and 5' phosphates of DNA.
It seals the nicks between the okazaki fragments left by the Pol beta. |
| Telomerase |
Reverse transcriptase
Uses RNA as a template to make DNA
Fills in the gap from overhang that can't be filled in by the DNA polymerase.
It also extends the length of the DNA |
Biology Lab Midterm
