EXAM 2 BIO 219 Questions With Complete
Solutions
How do we know that DNA is the hereditary material of organisms? Knowledge of DNA
and bacteriophage structure led to evidence that DNA is genetic material
What experiments led to the conclusion that DNA is hereditary material? 1. Griffiths
2. ...
How do we know that DNA is the hereditary material of organisms? Knowledge of DNA
and bacteriophage structure led to evidence that DNA is genetic material
What experiments led to the conclusion that DNA is hereditary material? 1. Griffiths
2. Avery, McCarty, MacLeod
3. Hershey, Chase
Describe the Griffiths experiment. Used 2 strains of pneumococcus, R is not toxic and
mice lived when injected, and S is toxic and mice died when injected. Heat-killed S bacteria
injected into mice did not kill the mice. However, when heat-killed S bacteria were injected
along with non-toxic R, the mice still died. This means that live 'R' bacteria were transformed
and became infectious 'S' bacteria.
Describe the Avery, McCarty, and MacLeod experiment. Same idea as the Griffiths
experiment, but done on plates. Used reverse genetics to determine what the "transforming
agent" was by taking one macromolecule off the plate at a time to determine whether colonies
lived or died.
, EXAM 2 BIO 219 Questions With Complete
Solutions
Describe the Hershey, Chase experiment. Labeled viruses with either 32P (blue)or 35S
(Red), observed whether proteins or DNA was transferred to bacterium. Sulfates are only in
proteins and Phosphates are found in DNA, RNA, and proteins.
What experiments contributed to the double-helix model of DNA? 1. Chargaff
2. Watson and Crick/Franklin, Wilkins & Gosling
Describe the Chargaff experiment. Isolate nucleotides from various organisms and
determine %'s. Hypothesized that A=T=C=G but was wrong! Actually, A=T and C=G.
Based on Chargaff's work, which of the following is true?
1. The %A in a mouse is approximately equal to the %A in a gorilla
2. %A = %C
3. %A + %C = %T + %G
4. Organisms have equal proportions of A, T, C and G 3. %A + %C = %T + %G
Describe what Hershey, Chase/ Franklin, Wilkins & Gosling did. Not an experiment, just
rearranged the pieces until they fit.
, EXAM 2 BIO 219 Questions With Complete
Solutions
What they knew:
DNA and RNA are composed of nucleotides
What they assumed:
The chemical reaction between 2 nucleotides
Model they built: Most double-stranded DNA in the cell is B-DNA
What are the key features of a nucleotide? Sugar, base, and phosphate
Draw a general nucleotide.
Where are the hydrogen bonds in the structure of DNA? Connecting nucleotides in base
pairs
Where are the covalent bonds in the structure of DNA? In the backbone, between the 3'
OH of the end of the existing strand, and the phosphate of the addition.
What direction does each strand of DNA move? 5' to 3'
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