Draw a labelled diagram to show how two nucleotides are joined together in a single strand of DNA.

Outline a basic technique for gene transfer.

Explain the process of translation.

Award [1] for each labelled item shown above.
Award [2 max] if the two nucleotides are not shown in a single strand.

plasmid removed from bacteria;
plasmid cleaved/cut open by restriction enzymes;
desired gene/DNA extracted from donor;
DNA from donor cleaved using same restriction enzyme;
results in sticky ends;
with complementary base sequences;
pieces of DNA from two organisms mixed;
ligase used to splice pieces (DNA);
recombinant plasmids formed;
insertion into host cells;

translation is the synthesis of proteins/polypeptide chain/specific sequence of amino acids;
translation occurs in cytoplasm/ribosomes;
uses information on the mRNA;
mRNA carries the genetic information of DNA;
mRNA binds to ribosome;
mRNA contains series of codons/base triplets;
tRNA binds with an amino acid and carries it to the ribosome;
tRNA has the anticodon that is complementary to the codon on the mRNA;
two tRNAs bind to a ribosome/mRNA at the same time;
(peptide) bond forms between two amino acids (carried by tRNA molecules to the ribosome);
the first tRNA detaches, ribosome moves along mRNA and another tRNA carrying an amino acid binds;
process repeats forming chain of amino acids/polypeptides;

Many candidates gained full marks for their diagrams of joined DNA nucleotides. As mentioned earlier, the problem for some candidates was their misinterpretation of “a single strand of DNA.” Though appropriate shapes were given, the bonding was improper.

In their outlines of gene transfer, candidates (as a group) eventually included each of the ten marking points. A number of candidates thoroughly understood the topic, while others wrote about meiosis and crossing over! The nature of the topic allowed candidates to express their ideas in a logical sequence.

The process of translation has been examined frequently on past papers. Though the topic involves many different molecular structures and events, some candidates seemed to correctly grasp much of the detail and overall result. Some excellent answers appeared. However, as in previous years, there were candidates who confused translation with transcription (perhaps a reading error after glancing at the question?) and those who mixed accurate with inaccurate information.