Genome sequencing produced a human reference

1. The Human Genome Project was an international programme that determined the order of bases across the human genome.
2. The project also identified the positions of genes within the sequence.
3. A human genome contains about $3\times 10^9$ base pairs and approximately $20,000$ protein-coding genes.
4. The completed sequence provides a reference genome against which individual genomes can be compared.

Genome data supports medicine

1. Comparing DNA sequences can identify alleles associated with inherited disorders.
2. This information can support diagnosis, carrier testing and estimates of disease risk.
3. Knowledge of a gene and its protein can guide the development of treatments.
4. Personalised medicine uses genomic information to help select a medicine or dose for an individual.
5. A risk allele does not guarantee disease because many conditions are affected by several genes and environmental factors.

Sequence comparisons reveal ancestry

1. More similar DNA sequences suggest that two individuals or populations share a more recent common ancestor.
2. Patterns of sequence similarity can therefore be used to investigate ancestry and past human migration.

Genomic information raises ethical issues

1. A statistical association between an allele and a disease does not always prove that the allele causes the disease.
2. Predictions may be uncertain and can cause anxiety for the person tested.
3. Genomic records require informed consent and secure storage because employers or insurers could misuse the information.