How is the human genome sequenced and analysed, and how does this support personalised medicine?
The sequencing and analysis of the human genome, the role of bioinformatics in comparing sequences, and the use of genomic and pharmacogenetic information in personalised medicine.
An SQA Higher Human Biology answer on human genomics, covering how the genome is sequenced and analysed, the coding and non-coding sequence of the genome, the role of bioinformatics and comparative genomics, single nucleotide polymorphisms, and how pharmacogenetics and genomics enable personalised medicine.
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What this dot point is asking
The SQA wants you to explain what sequencing the genome means, describe how bioinformatics analyses and compares sequences, explain how comparing genomes reveals relationships and disease links, and describe how genomic and pharmacogenetic information supports personalised medicine.
Sequencing and analysing the genome
The human genome is made up of two kinds of sequence. A small proportion codes for proteins (the genes), and a much larger proportion is non-coding. Non-coding DNA is not useless: some of it regulates transcription, switching genes on or off, and some is transcribed into functional RNA such as tRNA and rRNA. In humans only a small percentage of the genome actually codes for protein, so analysing the genome means making sense of far more than just the genes.
Bioinformatics and comparing sequences
Sequencing produces enormous data sets, far too large to analyse by hand. Bioinformatics is used to:
- Identify genes within the sequence and predict the proteins they code for.
- Compare sequences between different individuals, looking for differences linked to disease.
- Compare sequences between species (comparative genomics) to work out evolutionary relationships and how genes have changed over time.
Personalised medicine
The combination of cheap sequencing and bioinformatics makes it possible to read and analyse an individual's genome. This supports personalised medicine, in which treatment is matched to the patient's own genetic make-up.
An individual's genome can be used in two main ways. First, it can predict the diseases a person is at risk of developing, allowing earlier monitoring or prevention. Second, through pharmacogenetics, it can guide the choice and dose of medicines: because people metabolise and respond to drugs differently depending on their genes, doctors can select the most effective drug at the safest dose and avoid harmful side effects. This moves medicine away from a one-size-fits-all approach towards treatment tailored to the individual.
Examples in context
Example 1. Targeted cancer treatment. Sequencing the DNA of a patient's tumour can reveal which mutations are driving it. Doctors then choose a drug that targets that specific change, an example of personalised medicine guided directly by genomic data.
Example 2. Avoiding adverse drug reactions. Some people carry gene variants that make them break down a particular drug very slowly, so a standard dose can be dangerous. Pharmacogenetic testing identifies these individuals so the dose can be reduced, preventing harmful side effects.
Try this
Q1. State what is meant by sequencing a genome. [1 mark]
- Cue. Determining the order of the bases along the DNA.
Q2. Explain how an individual's genome can guide the dose of a medicine. [1 mark]
- Cue. Genes affect how a person metabolises a drug (pharmacogenetics), so the genome predicts their response and lets the dose be matched to them.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher 20193 marksExplain what is meant by sequencing the genome, and describe the role of bioinformatics in genomics.Show worked answer →
A 3-mark answer needs a definition of sequencing plus the role of bioinformatics.
Sequencing the genome means determining the order of the bases (the order of A, T, G and C) along all of an organism's DNA. The human genome includes a small proportion that codes for proteins and a large proportion that does not code for protein, some of which regulates transcription.
Bioinformatics is the use of computers and statistics to store, organise and analyse the large amounts of sequence data. It is used to compare sequences between individuals and between species, to identify genes, and to look for sequence differences linked to disease.
Award (1) order of bases determined, (2) genome includes coding and non-coding sequence, and (3) bioinformatics uses computing to analyse and compare sequence data.
SQA Higher 20223 marksExplain how knowledge of an individual's genome can be used in personalised medicine, and what is meant by pharmacogenetics.Show worked answer →
This is a 3-mark application question on personalised medicine.
Personalised medicine uses an individual's genome information to predict the diseases they are likely to develop and to guide the choice and dose of medicine. Knowing which alleles a person carries can show their risk of a particular condition and how they are likely to respond to a drug.
Pharmacogenetics is the study of how differences in a person's genes affect their response to medicines. Because people metabolise drugs differently depending on their genome, pharmacogenetics allows doctors to select the most effective drug and dose and to avoid harmful side effects.
Markers reward (1) genome used to assess disease risk, (2) genome used to guide drug choice and dose, and (3) pharmacogenetics defined as genes affecting drug response.
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