Ch 7 DNA Flashcards
What are the purine bases?
Adenine
Guanine
What are the pyrimidine bases?
Thymine
Cytosine
Uracil
What is Streptococcus pneumonia?
Pathogen that can cause benign infections
What do smooth strains of streptococcus pneumonia produce? (S) cells
Capsule called Virulent which are deadly
What are rough strains of streptococcus pneumonia called? (R) cells
Avirulent which are benign
What is the capsule of the smooth strain?
Extracellular polysaccharides that are sticky
Is the capsule deadly or harmless?
(S) cells containing capsule are deadly
What happens to the mice injected with (R) strain? (Avirulent)
They live; it’s harmless
No capsule renders it benign
What happens if mice are injected with live (S) strain cells (Virulent)?
It dies; (S) cells are virulent
Overwhelm immune system
What happens to mice injected with (S) cells that have been heated to kill the cells?
They live; Virus is dead
What happens to mice injected with live harmless (R) cells and heat killed (S) cells?
They die; The heat killed (S) cells broke open and transformed (R) cells.
(R) cells absorbed (S) cell DNA making them deadly
What did Griffith’s transforming principle conclude?
Something in (S) cell DNA, RNA and Proteins transformed (R) cells. Assumption was proteins were inherited
What are Degradative enzymes?
What do they destroy?
RNase - RNA only
Protease - Proteins only
DNase - DNA only
You can identify which degradative enzyme by which it destroys
What happened when DNase was added to heat-killed (S) cells?
DNase killed the DNA preventing capsule from growing
Was the transforming principle experiment a paradigm shift? Was the finding of DNA being the molecule of inheritance important?
Yes it was a paradigm shift
Won a Nobel prize
Discovered horizontal gene transfer
What is the 3 Dimensional structure of DNA?
Double Helix
RIght handed twist every 3.4 nm
Diameter of 2.0 nm
What did streptococcus do?
(R) strains absorbed DNA from the (S) strains and made the capsule
What is horizontal gene transfer?
Acquiring DNA from environment to make part of their chromosome
Does the number of pyrimidines always equal the number of purines?
Yes
How did Rosalind Franklin capture a photo of DNA
X-Ray Crystallography
2D image
Who determined the double helix shape of DNA?
Francis Crick and James Watson without any of their own experiments and won Nobel prizes
Who won the Nobel prize for discovering the structure of DNA?
Watson
Crick
Maurice Wilkins (Helix shape/Right-hand twist)
What is DNA composed of
Phosphate
Sugar
Base
How are A and T and G and C paired?
Hydrogen bonds
How many hydrogen bonds do A and T always have?
2
How many hydrogens bonds do G and C always have?
3
How are the strands of DNA held together?
Hydrogen bonds
DNA is anti-parallel T/F
True
In what direction is DNA copied?
5 Prime to 3 Prime
DNA is made to engage proteins T/F
True
What was the advantage of X-ray crystallography to measure DNA?
Scattering of X-RAYS produced a diagnostic pattern
What was the breakthrough Watson and Crick made building DNA models?
Pairing of Py and Pu were consistent with 2nm diameter
Determined DNA was a double helix
What did the Hershey and Chase experiment conclude?
DNA and NOT protein is in genetic bacteriophages; Singled out that DNA was responsible for inheritance
Why is DNA held together by hydrogen bonds?
Hydrogen bonds are easy to break
DNA is half old and new strands T/F
True
Is DNA replication semi-conservative?
Yes
What did Meselson and Stahl find int their experiment?
DNA replication is semiconservative
How do N14 and N15 differ?
One neutron
What does DNA polymerase do?
- Enzymes that put in complementary base
- Proofreads
- 1 in every billion nucleotides it makes a mistake
What happens to DNA before it is replicated?
It is pulled apart by replisome
What is a replisome?
Protein that carries out replication and unwinds DNA for it to be copied
What do DNA polymerase Dimers do?
Ensure DNA is simultaneously copied but only in 5 prime to 3 prime direction
Why is it important for bio students to ID the 5’ and 3’ prime carbons in Deoxyribose?
Knowledge of DNA structure is important for understanding biological processes
Avery, Macleod, and McCarty followed up Griffith’s transforming principle by treating heat killed (S) cells then added (R) cells. What did it conclude?
Only solutions with intact (S) cell DNA resulted in transformation
Hydrogen and Oxygen are highly electronegative? T/F
True
What is complimentary base pairing?
Bases like PY and PU pairing together
When the (S) cell was heat killed and broke open, What did the benign (R) cells absorb to make them deadly?
(S) cell DNA
(R) cells acquired the genes that formed capsule
What did Griffth’s experiment find?
How genetics and inheritance work
What is the molecule of inheritance?
DNA
What is the portion “Deoxyribose” made up of?
Phosphate and sugar backbone
What was Chragaff’s findings?
Purines always equaled Pyrimidines
