4.1 DNA, genes and chromosomes practise questions

Question 1

Describe how a gene is a code for the production of a polypeptide. Do not
include information about transcription or translation in your answer.

Answer 1

1. (Because) base/nucleotide sequence;
2. (In) triplet(s);
3. (Determines) order/sequence of amino acid sequence/primary
   structure (in polypeptide);

Question 2

Describe how a phosphodiester bond is formed between two nucleotides
within a DNA molecule.

Answer 2

) 1. Condensation (reaction)/loss of water;
2. (Between) phosphate and deoxyribose;
3. (Catalysed by) DNA polymerase;

Question 3

Define ‘non-coding base sequences’ and describe where the non-coding
multiple repeats are positioned in the genome.

Answer 3

DNA that does not code for (sequences of) amino acids (introns)
2. (Positioned) between genes;

Question 4

Not all mutations in the nucleotide sequence of a gene cause a change in
the structure of a polypeptide.
Give two reasons why

Answer 4

1. Triplets code for same amino acid
   Accept: DNA/code/triplets are degenerate
2. Occurs in introns /non-coding sequence;

Question 5

WHat is a homologous pair

Answer 5

(Two chromosomes that) carry the same genes;