7.3.1 Restriction Fragment Length Polymorphisms: Genetic Markers

Question 1

Restriction Fragment Length Polymorphisms (RFLPs)

Answer 1

• differences in homologous sequences of DNA that can be detected between individuals.
  • RFLP analysis involves exposing homologous segments of DNA to a restriction enzyme and separating the resulting fragments by electrophoresis.
  • Since RFLPs result from differences in DNA sequences, they can be passed along to offspring.
  • RFLPs that are associated with particular genes can serve as genetic markers for those genes.
• small differences in DNA sequences between individuals. RFLPs are detected by examining the different restriction fragments that result after exposure to the same restriction enzyme.
• When two homologous pieces of DNA have different
  restriction fragments after exposure to restriction enzyme, the pieces are said to be polymorphic.
• A single base-pair mutation can cause a difference in RFLP patterns.
• In the diagram to the left, DNA piece 1 has two restriction enzyme cut sites. Three fragments of DNA will result after the DNA is exposed to the restriction enzyme: fragments w, x, and y.
• As seen in DNA piece 2, the difference in a single base pair causes a restriction enzyme cut site to be lost. Now only two fragments of DNA will result after the DNA is exposed to restriction enzyme: fragments y and z.
• RFLPs can be passed to offspring like genes and can be used
  as genetic markers for particular genes.
• For example, a particular RFLP could be linked to a disease, such as cystic fibrosis. If the RFLP is found in all carriers of cystic fibrosis, then it can be used as a genetic marker for that disease.

Question 2

The technology used to detect RFLPs can detect differences between

Answer 2

• specific genes

Question 3

Restriction fragment length polymorphisms

Answer 3

• are an indication of a difference in the DNA sequences of the two fragments initially treated with the restriction enzyme

Question 4

Restriction fragment analysis relies on the fact that

Answer 4

• restriction enzymes cut at specific DNA sequences.
• a particular fragment of DNA will show a distinctive banding pattern when cut with a specific restriction enzyme.
• gel electrophoresis can sort DNA fragments clearly and repeatably by size.

Question 5

Restriction fragment analysis can distinguish between two alleles of the same gene

Answer 5

• only if the difference between the two alleles affects the location of a restriction site