7.1 DNA Structure and Replication

Question 1

Outline Hersey and Chase

Answer 1

• Proved that DNA is the genetic material
• Grew viruses in radioactive sulfur (in protein not DNA) or radioactive phosphorus (in DNA not protein)
• Infected E.coli bacteria with the viruses
• Seperated bacteria and virus via centrifugation, produced a pellet
• The pellet contained radioactive phosphorus

Question 2

What did Rosalind Frankling do?

Answer 2

• Worked at Kings College in London during the 1950’s
• Used X-ray crysallography to obtain a 3d picture of DNA
• Showed that DNA is double stranded, that phosphate groups need to be on the outside, and that DNA is a helix

Question 3

What did Watson and Crick do?

Answer 3

• Used Franklin’s picture to help them in creating a DNA model
• Found that the bases can not be too far away from eachother
• Found that a purine needs to be bonded to a pyrmidine
• Led to the hypothesis of semi-conservative replication

Question 4

Purines

Answer 4

• Adenine
• Guanine

Question 5

Pyrmidines

Answer 5

• Cytosine
• Uracil
• Thymine

Question 6

What DNA is associated with histones?

Answer 6

Eukaryotic DNA

Question 7

What is considered naked DNA?

Answer 7

Prokaryotic DNA, since it is not associated with histones

Question 8

What does histones do?

Answer 8

They pack eukaryotic DNA into nucleosomes

Question 9

What are nucleosomes?

Answer 9

A nucleosome is 8 histones with DNA wrapped around them. They are connected via short sections of DNA

Question 10

What are the bennefits of nucleosomes?

Answer 10

Nucleosomes contribute to supercoiling, which allows long strands of DNA to be packed in a smaller space in the nucleus. This helps eukaryotes in packing their large genome.