DNA Genes Chromosomes 2016-2021

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

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

Question 3

show three differences between DNA in the nucleus
of a plant cell and DNA in a prokaryotic cell.

Answer 3

Introns v no introns;
Linear v circular;
histones/proteins v no histones/proteins;

Question 4

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

Answer 4

DNA that does not code for protein/polypeptides
(Positioned) between genes;

Question 5

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

Answer 5

• mutations occur in introns
• code is degenerate

Question 6

What is a homologous pair of chromosomes?

Answer 6

2 chromosomes that carry the same genes

Question 7

similarities the DNA in eukaryotic cells with the DNA in
prokaryotic cells.

Answer 7

-identical nucleotide structure
-nucleotides both joined by a phosphodiester bond

Question 8

Give one other difference between the structure of a DNA nucleotide and
the structure of an RNA nucleotide.

Answer 8

• Deoxyribose pentose sugar
• ribose sugar
  or
• thymine in DNA and Uracil in RNA

Question 9

what does structure mean?

Answer 9

what something is made up of

Question 10

what does compare mean?

Answer 10

similarities and differences

Question 11

Describe the structure of DNA.

Answer 11

1. Polymer of nucleotides;
   Accept ‘Polynucleotide’
   Accept for ‘phosphate’. phosphoric acid
2. Each nucleotide formed from deoxyribose, a phosphate (group) and
   an organic/nitrogenous base;
3. Phosphodiester bonds (between nucleotides);
4. Double helix/2 strands held by hydrogen bonds;
5. (Hydrogen bonds/pairing) between adenine, thymine and
   cytosine, guanine;

Question 12

Describe how the separation of strands occurs.

Answer 12

1. DNA helicase;
2. Breaks hydrogen bonds between base pairs/

Question 13

1. the role of the single-stranded DNA fragments

Answer 13

acts as a template determining sequence of amino acid s