3.6 Nucleic acids

Question 1

what do nucleic acids contain

Answer 1

CHO + nitrogen + phosphorus

Question 2

what are the 3 components on nucleotides

Answer 2

• pentose monosaccharide
• phosphate group
• nitrogenous base

Question 3

in DNA, what are the 4 bases divided into

Answer 3

• pyrimidines = small bases with single carbon ring structures
• purines = large bases with double carbon ring structures

Question 4

pyrimidines

Answer 4

T and C

Question 5

purines

Answer 5

A and G

Question 6

structure of DNA

Answer 6

• 2 strands of double helix held together by hydrogen bonds between bases
• each strand as phosphate group (5’) at one end and hydroxyl group (3’) at other
• anti parallel strands running in opposite directions

Question 7

complementary base pairing

Answer 7

A and T = 2 hydrogen bonds
C and G = 3 hydrogen bonds

purine always binds to pyrimidine maintaining constant distance between backbones

equal amounts of A and T/ C and G

Question 8

what is the pentose sugar in DNA vs RNA

Answer 8

DNA = deoxyribose

RNA = ribose

Question 9

RNA

Answer 9

• essential role in transfer of genetic info from DNA—> proteins
• mRNA leaves nucleus as DNA is too large
• T is replaced by uracil (U)

Question 10

what happens to RNA molecules after protein synthesis

Answer 10

degraded in the cytoplasm

phosphodiester bonds = hydrolysed
RNA nucleotides =released and reused

Question 11

explain the process of DNA extraction

Answer 11

1. grind sample (breaks down cell walls)
2. mix sample with detergent (breast down cell membrane to release cell contents into solution)
3. add salt (breaks hydrogen bonds between DNA and water)
4. add protease enzyme (break down proteins associated with DNA in nuclei)
5. add layer of alcohol on top of sample (causes DNA to precipitate out of solution)
6. DNA is seen as white strands between sample and alcohol layer, picked up by ‘spooling’ on a glass rod