Theme 1A experiments of DNA as hereditary molecule

Question 1

What are the three classical experiments?

Answer 1

1. Griffith: Found a substance that genetically transform pneumonia.
2. Avery, Macleod and Mccarthy: Identified that DNA transformed pneumonia to an infective form.
3. Hershey and Chase: final piece to DNA as hereditary molecule.

Question 2

Which strain allowed for virulence? (experiment 1)

Answer 2

Smooth strain, rough strain was non-virulent.

Question 3

What is transforming principle? (experiment 1)

Answer 3

The killed S cells could transform R cells genetically to virulent. The transformation is permanent and heritable.

Question 4

What did Avery, Macleod and Mccarthy prove?

Answer 4

That DNA was responsible for transforming principle.

Question 5

What are two possible life cycles for a virus?

Answer 5

lytic cycle: massive reproduction of virus resulting in host cell lysis (disintegration).
lysogensic cycle: replication of viral genome, whose DNA is integrated with bacterial chromosome.
(lysogenic cycle to switch to lytic cycle given viral DNA escapes bacterial chromosome).

Question 6

How did Hershey and Chase identify what was injected into E.coli by bacteriophage.

Answer 6

They used the isotope 32P for DNA, and 35S on protein.
Then 32P was found in E.coli cells and progeny bacteriophage, but not within detached bacteriophages.
35S was found in detached bacteriophages, meaning it was not injected.

Question 7

Explain how gene expression and protein expression determine phenotype.

Answer 7

Gene: produces RNA and protein
Protein: the type and abundance of protein in a cell.