DNA Structure and Replication (7.1)
SECTION LINKS: |
NOTES HLHL JEOPARDY GAME REVIEWFor Core Material See
|
The Hershey & Chase Experiment
Throughout the 1900s most scientists believed that protein held the key to our inheritance. Yet, it was theory without evidence. But in:
|
|
The Experiment:
Due to the discovery or radioactive isotopes of various elements, Hershey and Chase were able to develop an experiment that could track where the protein and DNA went.
|
Rosalind Franklin & Maurice Wilkins
Roslind Franklin and Mauric Wilkins were co-workers at King's College in London. Franklin is best known for her work on X-ray Crystallography using DNA.
|
|
DNA Structure suggests a method for replication
One of the significant aspects of the discovery of the structure of DNA was that the structure immediately suggested a method for replication. Because of the hydrogen bonding in the middle between bases AND the complementary base pairs (A-T/ C-G), scientists immediately began to ask the question- it whould be able to replicate and produce exact copies of itself. This led to the competeing theories of DNA replication at the time and ultimately Meselson & Stahl's experiment that determined semi-conservative replication.
DNA Replication
DNA replication is one of the most complicate, elaborate, and beautiful processes in biology. It's sophistication should make you appreciate the complexity of life, as well at the nature of the age old question- how did that first cell originate?
Molecular Mechanisms |
A few reminders:
|
Stages of Replication:
Initial Steps:
Initial Steps:
- Gyrase unwinds the double helix
- Helicase splits the hydrogen bonds of the two strands.
- Single Stranded binding proteins (SSBPs) bind to the single strands to stabilize them until replication occurs
- DNA primase adds a short length of RNA at the origin of replication (called a primer) allowing DNA polymerase III to bind to the DNA strand.
- DNA polymerase III moves in the direction of replication (5'--> 3') adding complementary bases
- DNA Primase adds a short length of RNA (called a primer) allowing DNA polymerase III to bind.
- DNA polymerase III adds complementary bases moving 5' ---> 3' however, it is moving in the opposite direction of replication
- These steps are repeated as new single stranded DNA is made avaliable by the movement of the helicase.
- Results in sections on the lagging strand called Okazaki Fragments
- DNA Polymerase I replaces the RNA primers with DNA nucleotides
- DNA Ligase seals the nicks in the DNA strands making it one continuous strand
- Both DNA polymerase I and III proofread the strand for base pairing mistakes.
|
|
Short Tandem Repeats
DNA profiling: process of determining a individual's DNA characteristics. Usually done using PCR<, Restriction Enzymes, and Gel Electrophoresis.
|
|
|
Visualization Software
Through visualization software we can actually see what many molecules look like. Use a site like this, to search for what you are interested in. Here are a few to look at.
tRNA synthatase tRNA in a tRNA synthatase- note the tRNA embedded in the enzyme. Note where the active sites may be located tRNA and ribosome - note the location of the tRNAs in the small ribosomal subunit, as well as the location of where the mRNA would be. |
- Home
-
DP Biology Core
-
HL Biology Only
-
DP ESS SL
- Foundations in ESS (Topic 1) >
- Ecosystems and Ecology (Topic 2) >
- Biodiversity and Conservation (Topic 3) >
- Water, Food Production Systems and Society (Topic 4) >
- Soil Systems and Society (Topic 5) >
- Atmospheric Systems and Society (Topic 6) >
- Climate Change and Energy Choice (Topic 7) >
- Human Systems and Resource Use (Topic 8) >
- Biology 1
- All things Lab
- More DP