Genetic testing may be used to find out if an ❌ has a genetic disease - a disease which they have ❌ and which is a result of a defect in their DNA.
To investigate a person’s DNA, ❌ blood cells are used because they are easy to obtain from a blood sample, and (unlike ❌ blood cells) they have a nucleus containing the DNA.
1. Isolation of DNA from white blood cells
A small quantity of blood has chemicals added to it. The chemicals split open the red cells. The sample is then put into a centrifuge and spun very rapidly so that the white cells form a ❌ at the bottom of the tube.
The pellet of white blood cells is then ❌ in a liquid. More chemicals are added which split open the cell membranes and release the DNA from the ❌.
The DNA is collected and then ❌ (more copies of it are made) so that there is enough to test. The DNA is then broken up into smaller sections using ❌ and put onto a special gel. An electrical ❌ is applied, and the pieces of DNA separate out along the gel.
2. Gene Probe
A gene ❌ is a short section of single-stranded DNA that has a ❌ chemical attached to it which will glow under UV light. The chemical is added to a length of DNA which has the ❌ base sequence to the gene that codes for a particular disease, eg cystic fibrosis.
3. Adding the gene probe to the sample DNA
The separated pieces of DNA on the gel are ‘blotted’ to split the DNA into single strands. The gene probe is added and if the gene the scientist is searching for is present, the gene probe will ❌ to it because it has a complementary base sequence to the gene being ❌.
4. Using UV light
The gel is then viewed under ❌ light. If the gene is present, the gel will glow at that point. The gene has therefore been identified as being ❌ in the person’s DNA.
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complementary
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