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- author "Ant"
- tags "Gene Expression Tony Russell Biology Genetics DNA"
- description "Gene Expression"
- fileName "Gene Expression 1 - Chapter Two"
- freezingBlueDBID -1.0
- Freidrich Miescher Isolated "Nuclein". What is "Nuclein" now known as?
What did Griffith do in his experiment?
He infected mice with Streptococcus Pneumoniae, of both Living R-strain,and heat killed S-strain. Through this he discovered transformation of the live R-strain.
What did Avery do in his experiment?
He followed on from Griffith by using enzymes to degrade the molecules in question for heredity.
Trypsin and Chemotrypsin break down...?
What is Chromatin
A complex of DNA and its associated proteins.
What were the purpose of Nucleases in Avery's experiments?
Nucleases, more precisely Ribonuclease and Deoxyribonuclease broke down RNA and DNA respectively. In this way it was possible to determine hereditory material in Transformation.
Briefly explain Ultracentrifugation. State how it helped confirm DNA for Avery.
- Ultracentrifugation is centrifugation (seperation by mass, high speed spinning) at especially high speeds.
- Avery found the hereditory molecule quickly dropped to the bottom of the tube, indicating an large, heavy molecule, such as DNA.
Briefly explain Electrophoresis. State how it helped Avery confirm DNA as hereditory.
- Electrophoresis analysis by observing behaviour of a substance in an electric field.
- Avery found the hereditory material responded greatly to an electric field. DNA is a negatively charged molecule, as a result Avery's experiments suggest DNA.
Avery used UV absorbtion to determine DNA as the hereditory material. What results suggested this?
The peak absorbtion was wound to be ~260nm. Characteristic of DNA.
What wavelength of UV light does DNA absorb most readily?
What wavelength of light do proteins absorb most readily?
Avery used Elementary Chemical Analysis to determine the ratio between phosphorus and nitrogen.
- This was low suggesting DNA
- (Proteins have a lot of nitrogen but no phosphorus)
- (DNA also has a lot of nitrogen, but it has a lot of phosphorus too. This gives a low ratio.)
What was chagraff's contribution to understanding DNA?
Chagraff's rules. Chagraff discovered that bases were not found in equal proportions in DNA.
What bacteriophage did Hershey and chase use to demonstrate DNA as hereditory?
What is a Nucleoside?
Base + Sugar = Nucleoside (No phosphate)
What is a Nucleotide?
Base + Sugar + Phosphate = Nucleotide
Nucleosides are named based on their base. For each base, state its DNA name
- (Uracil is not common in DNA)
Name each base in RNA nuceosides...
- (Thymine is not common in DNA)
Phosphates on a nucleotide are termed alpha, beta and gamma with respect to the exocyclic 5' carbon.
That is all...
Define Exocyclic. Give an example.
Exocyclic means "outside of the ring". In genetics, this often refers to the 5' carbon on the nucleotide sugar.
Charge charge repulsion from the sugar-phosphate backbone is destabilizing. What stabilizes this?
Captions in aqueous solution.
What is helical pitch?
Helical pitch is the number of base pairs per helical turn.
What is the helical pitch of DNA?
10 base pairs or 3.4nm pass pairs are 0.34nm apart)
What is the helical width of DNA?
2nm in B-form DNA
Right handed DNA can also be called ___. It indicates that the structure spirals to the right.
What is the process for naming nucleotides?
- Name the base (considering which type of base it is), determine which carbon the phosphate lies on, then state how many phosphates, e.g,
What can cause DNA to bend?
Either proteins binding with major and minor grooves, or A-T rich DNA sections.
What are the characteristics of B-form DNA?
- -> Right handed
- -> Neatly stacked bases
- -> It has intermediate helical width and pitch
What are some characteristics of Z-form DNA?
- -> Largest helical pitch (more space between bases)
- -> Smallest helical width
- -> Left handed
- -> Bases "zigzag"
What are some characteristics of A-form DNA?
- -> Large Helical Width
- -> More bases per turn (shorter turn length)
- -> Right Handed
When my Z-form DNA arise?
A -GCGC- pattern in the correct aqueous conditions will form Z-DNA
Why is Z-form DNA important?
Some proteins only recognize Z-form DNA. Therefore is is useful for gene expression.
What is the DNA melting temperature?
The point at which 50% or more of DNA molecules are completely seperated.
What affects DNA melting temperature?
- -> Strand length
- -> Composition (G-C content)
- -> Aqueous conditions (Salinity)
- -> Presence of Formanide and Urea (Destabillizing)
Why do Formanide and Urea destabilize the helix?
They compete for hydrogen bonding interactions.