Nucleotides and nucleic acids

Question 1

state the components of a DNA nucleotide (3)

Answer 1

• deoxyribose sugar
• phosphate group
• purine/pyrimidine base

Question 2

Describe how the structure of RNA differs from that of DNA (2)

Answer 2

has ribose ;
uracil / U, instead of, thymine / T ;
single stranded ;
3 forms / AW ;

Question 3

Describe how a DNA molecule is replicated (7)

Answer 3

untwist / unwind ;
unzip / described ;
H bond breaks ;
both strands act as template ;
(aligning of) free (DNA) nucleotides ;
complementary, base / nucleotide, pairing ;
C to G and T to A / purine to pyrimidine ;
hydrogen bonds reform ;
sugar-phosphate back bone forms ;
(using) covalent / phosphodiester, bond ;
semi-conservative replication ;
DNA polymerase ;

Question 4

Suggest how changing the sequence of DNA nucleotides could affect the final product the DNA codes for (2)

Answer 4

There will be a different sequence of amino acids (primary structure) which leads to a different protein forming. This means the protein may no longer function or have a different function

Question 5

State the role of a gene (1)

Answer 5

codes for a specific polypeptide

Question 6

Explain how the structure of DNA allows replication

Answer 6

DNA is double stranded (both strands act as a template). hydrogen bonds easily break/form between bases. which leads to complementary base pairing. purines are only able to bind to pyrimidines. There is H bonds between A, T (2 H bonds) and C, G ( 3 H bond)