nucleic acids

Draw labelled diagrams to show the structure of RNA nucleotides and how they are linked together to form a molecule of RNA (4)

a. ribose drawn as pentagon and labelled sugar/ribose;
b. base drawn with correct link to (C₁ of) ribose and labelled base/nitrogenous base;
c. phosphate drawn with correct link to (C₅ of) ribose and labelled P/phosphate;
d. two (or more) ribonucleotides drawn with correct link (C₃ to C₅)

Explain how the two strands of the DNA double helix are held together (2)

1. hydrogen bonding between nucleotides / bases;

2. complementary base pairs;

3. adenine-thymine and cytosine-guanine form base pairs (between the two strands with H-bonding);

4. 2 bonds between A and T, while 3 bonds between C and G

Describe the structure of the DNA molecule (5)

a. two stranded/double helix ✔

b. antiparallel / strands running in opposite directions
OR
one strand organized 5’ to 3’ and the other 3’ to 5’ ✔

c. sugar-phosphate backbone ✔

d. each strand formed by chains of nucleotides ✔

e. each nucleotide is formed by a phosphate, a deoxyribose and a base / annotated diagram of a nucleotide clearly indicated as a nucleotide ✔

f. the bases are adenine, guanine, cytosine and thymine ✔

g. strands held together by hydrogen bonds (between complementary base pairs)
OR
A pairs with T and C pairs with G ✔

Sketch the complementary strand to complete the section of a DNA diagram (3)

Distinguish between the structures of DNA and RNA (3)

DNA is double stranded, RNA is singe stranded

DNA: deoxyribose, RNA: ribose

DNA: thymine, RNA: uracil

DNA: helical RNA: variety of forms → mRNA, tRNA, rRNA

draw a labelled nucleotide (3)