Explain the biochemical evidence for the common ancestry of organisms on Earth.

all organisms use DNA as genetic material;

same four (nucleotide) bases makes up DNA in all organisms;

number of mutations reflect differences between organisms;

all organisms use the same genetic code / minor differences;

genetic code is degenerate/OWTTE;

all organisms use the same 20 amino acids;

function of proteins constant between species;

protein/molecule examples; (eg hemoglobin, cytochrome, chlorophyll)

only left-handed amino acids have been observed in living organisms;

although right-handed amino acids will have been available;

only right-handed glucose/carbohydrates used in organisms;

similarities in glycolysis/metabolic pathways;

all use RNA/same enzymes in transcription/translation;

Candidates had more difficulty with this question than with questions requiring longer answers in the other options, but many nevertheless provided good answers and managed to gain all the marks; those who were less successful confused biochemical evidence with origins of life.