DNA Sequencing/Variation
Terminologycontinued
Molecular Diagnostics
(MDx) Review 566
TERM EXPLANATION
Polymorphism
Single nucleotide polymorphism (SNP)
Restriction endonucleases
Restriction site (recognition site)
Palindrome
Restriction digest
Restriction pattern (RFLP profile)
Restriction fragment length
polymorphisms (RFLPs)
Variation in DNA sequence that occurs in at least 1% of population. Some cause suscepti-
bility to disease, affect response to drugs.
“Snip.” Variation in single base. Most common type of variation in human genome. May or
may not cause disease.
Bacterial enzymes used to cut DNA at specific sites. Used to produce short fragments for
electrophoresis.
Nucleotide sequence recognized by restriction endonuclease. Most are palindromes.
Nucleotide sequence that reads same in both directions, e.g., the complementary strand to
5’-CATG-3’ is 3’-GTAC-5’. Since reading is from 5’ to 3’ direction, both are read as CATG.
DNA fragments formed by action of restriction endonucleases on DNA.
Pattern of DNA fragments produced following digestion with restriction endonucleases.
Fragments separated by gel electrophoresis. Stained with ethidium bromide & viewed
under UV light or blotted onto nitrocellulose membrane & detected with labeled probe
(Southern blot).
Differences in restriction patterns due to variations in nucleotide sequences that change
where restriction enzymes cleave DNA. Useful in forensic & paternity testing, detection of
genes associated with specific diseases, ID of microorganisms.
