2.6 strucutre of DNA and RNA

Question 1

nucleic acids are composed of

Answer 1

recurring monomeric units – nucleotides

Question 2

3 parts of a nucleotide

Answer 2

1. nitrogenous base
2. pentose sugar
3. phosphoric acid

Question 3

differences in DNA and RNA 4

Answer 3

1. nitrogenous base/ base composition:
   CGAT vs CGAU
2. pentose sugar
   deoxyribose vs ribose
3. number of strands
   double stranded vs single stranded
4. stability
   more stable vs less stable (Versatile)

Question 4

drawing nucleotides
IMAGINE ONE RN

Answer 4

circle (phosphate group) – 5-carbon pentose sugar (pentagon) ^– rectangle (nitrogenous base)

• rectangle attached to the 1’-carbon atom (right point)
• circle attached to 5’-carbon atom (left point) and angled upwards

Question 5

how are nucleotide monomers linked into a single strand

Answer 5

condensation reaction
- phosphate grp of one attaches to sugar of another molecule (at 3’-hydroxyl (-OH) group)
- phosphodiester bond forms (water by product)

Question 6

RNA vs DNA but its the thing on 2’ carbon of the pentose sugar

Answer 6

RNA has OH
DNA has H

Question 7

3 types of RNA

Answer 7

• messenger RNA mRNA
  transcript copy of gene which encodes a specific polypeptide
• transfer RNA tRNA
  carries polypeptide subunits (AA) to organelle responsible for synthesis (ribosome)
• ribosomal RNA rRNA
  a primary component of the ribosome, resposible for its catalystic activity

Question 8

DNA polynucleotide chains of DNA are held tgt via

Answer 8

hydrogen bonding

adenine (two bonds) thymine
guanine (three bonds) cytosine

Question 9

DNA strand strucutre

Answer 9

• double helix
• run in opposite directions (for bases to face each other and pair) : antiparallel

Question 10

what did crick and watson discover

Answer 10

the structural organisation of DNA
- composed of nucleotides made up of a sugar, phosphate and base
- composed of equal number of AG(purines) and CT(pyrimidines)
- DNA has a helical structure

Question 11

crick and watson assembled a DNA model that demonstrated: 3

Answer 11

• DNA strands are antiparallel and form a double helix
• DNA strands pair via complementary base pairing
• outer edges of bases remain exposed (allows access to replicative and transcriptional proteins)

Question 12

faults of early crick and watson model

Answer 12

• triple helix
• bases on the outside and sugar-phosphate residues in the centre
• nitrogenous bases did not demonstrate complementarity