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The control of gene expression - A Level only (3.8)›Differences in individuals' DNA used for identification and diagnosis - AL only (3.8.4.2)

Differences in individuals' DNA used for identification and diagnosis - AL only (3.8.4.2)

An overview of differences in individuals' DNA used for identification and diagnosis - AL only (3.8.4.2) from AQA A level Biology
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A DNA probe is a short, single-stranded piece of DNA.

The DNA probe is labelled in one of two ways:

  • Radioactivity: nucleotides containing the radioactive isotope can be used, which allows the DNA probe to be identified using X-ray film.
  • Fluorescence: nucleotides can be chemically altered to produce fluorescence under certain conditions.
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The image depicts two types of DNA probes: 'Radioactive DNA probe' and 'Fluorescent DNA probe'. Under 'Radioactive DNA probe', it states 'Phosphate groups in DNA probe contain 32P'. Below this, two parallel DNA strands are shown: the upper strand labeled 'A C C A G T' and the complementary lower strand labeled 'A T G G T C A T'. An arrow points to the lower strand with the label 'Complementary DNA'. On the right, under 'Fluorescent DNA probe', a green oval labeled 'Fluorescent group' is attached to the upper strand labeled 'A C C A G T'. The complementary lower strand is labeled 'A T G G T C A T' with an arrow pointing to it labeled 'Complementary DNA'.
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DNA probes can be made to identify specific genes or DNA sequences. The DNA probe is made to be complementary to the section of DNA.

  1. Denaturation – DNA is separated into two separate strands.
  2. Hybridisation – the DNA probes are added and attached to the complementary section of DNA.
  3. Identification – the DNA probe can be identified using radioactivity or fluorescence.
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DNA probes can be used for:

  • Genetic screening: identifying faulty alleles which could cause genetic disorders, which can then be used in genetic counselling.
  • Drug responses: certain alleles can affect how a person responds to specific drugs; this can be used to decide which medications or dosages a person receives.
  • Oncogenes: detecting different oncogenes within tissues, which can lead to increased mitosis and tumour formation.
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Genetic counselling involves providing people with advice and information to help them make informed choices.

A table with three columns and three rows. The columns are labeled 'Application,' 'Screening,' and 'Potential options discussed.' Row 1: 'Becoming parents' under 'Application,' 'Risk of passing on a genetic disorder' under 'Screening,' and bullet points under 'Potential options discussed' listing 'Genetic testing of parents,' 'Embryonic or foetal testing,' and 'Decisions whether or not to have biological children.' Row 2: 'Treatment decisions' under 'Application,' 'Genetic mutations of cancer cells' under 'Screening,' and 'Certain genes within the cancer cells can help indicate which treatments could be most effective' under 'Potential options discussed.' Row 3: 'Disease risk' under 'Application,' 'Screening for genes related to an increase cancer risk, such as the BRCA1 and BRCA2 genes' under 'Screening,' and bullet points under 'Potential options discussed' listing 'Risks of developing disorders or cancers,' 'Screening decisions, such as frequency or age of when to start screening,' and 'Prevention decisions, such as a preventative mastectomy.' The table is © Medify.
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