Schwabe 1 DNA structure & replication

Question 1

Evidence for DNA structure

1) Transformation of pneumococci in vivo

Answer 1

Steptococcus pneumonia has 2 forms=> ‘smooth’, make polysaccharide capsule PATHOGENIC, killed by heat. ‘rough’ non-pathogenic, no capsule. => ‘rough’ pneumococci could be TRANSFORMED by something from dead smooth bacteria (in mice)

Question 2

Evidence for DNA structure

DNA is transforming principle

Answer 2

crude extract from dead, smooth pneumoccoi transformed rough strain in vitro with protein-free extract activity destroyed by DNase.

Question 3

Evidence for DNA structure

DNA is hereditary material

Answer 3

Used radiolabelled phages: DNA =32P, Protein = 35S => infect E.coli
Infection interrupted by shearing => culture centrifuged => DNA not protein had been injected

Question 4

PHAGES

Answer 4

= DNA + protein, viruses that infect bacteria & multiply inside cells.

Question 5

DNA stands for

Answer 5

deoxyribonucleic acid

Question 6

Components of DNA

Answer 6

4x nitrogenous bases, 5carbon deoxyribose sugar, phosphate.

Question 7

NUCLEOSIDE:

Answer 7

base attached to C’ on sugar joined by B, -glycosidic cond N-C

Question 8

Purines

Answer 8

Adenine

Guanine

Question 9

Pyrimidines

Answer 9

Cytosine

Thymine

Question 10

Base x5

Answer 10

Adenine
Guanine
Cytosine
Thymine
uricil

Question 11

Nucleoside x5

Answer 11

adenosine
guanosine
cytidine
thymidine
uridine

Question 12

Polynucleotide:

Answer 12

Polynucleotide: Nucleic acids are polyneucelotides, polymers of nucelotides, joined by phosphodiester bond, 3’-> 5’ phosphate ribose backbone.

Question 13

Sequence hypothesis:

Answer 13

entire science of molecule base sequence in DNA determine amino acid sequence in protein.

Question 14

anti-parallel

Answer 14

3’-> 5’ phosphate ribose backbone. 5’end & 3’ ends, in double stranded DNA 2 strands are anti-parallel => polarity