structure of DNA and RNA

Question 1

nucleic acids

Answer 1

• composed of nucleotides which are the “building blocks”
• 3 components: nitrogenous bases, sugar (pentose), phosphate (phospho-diester bond)

Question 2

nitrogen-containing bases

Answer 2

2 types: purines and pyrimidines
purines: 2 ring structures - adenine and guanine
pyrimidines: 1 ring structures - cytosine, thymine and uracil (in RNA)

Question 3

how are nucleotides joined

Answer 3

by phosphodiester bonds
- links C-3 of one sugar to C-5 of another
-

Question 4

DNA polarity

Answer 4

• one end is 3’ one is 5’
• 5’ end has a free 5’ carbon
• 3’ end has a free phosphate group
• polarity allows enzymes to replicate in right direction

Question 5

nucleotide pairs

Answer 5

A and G (via 2 H-bonds)
C and T (via 3 H-bonds)
pairs are found in equal proportions in double-stranded DNA

Question 6

William Astbury discovery

Answer 6

X-ray diffraction analysis showed that DNA is a polymer of stacked bases

Question 7

the Watson-Crick model

Answer 7

• %A = %T, %C = %G
• helical structure
• bases stuck like coins over each other

Question 8

DNA assumptions

Answer 8

• DNA is a double helix
• two strands were anti-parallel
• the sugars form a phosphate backbone
• the bases are held together by H-bonds

Question 9

how can you break apart DNA

Answer 9

• heat is needed
• GC value = how much heat is needed to break apart strands
• more H-bonds = more heat needed