Genetic Polymorphisms

Question 1

Polymorphism

Answer 1

A heritable change in DNA sequence which occurs at a frequency greater than that sustained by mutation.
In other words, a common sequence
variation, typically more than 1% of the
population.

Question 2

SNP (snips): Single Nucleotide Polymorphism

Answer 2

• A single base change in sequence.
• Basically the same as a point mutation only occurring at a higher frequency and in most cases having no phenotypic consequence.
• In those cases where there is a phenotype, the SNP is associated with a predisposition syndrome

Question 3

RFLP: Restriction Fragment Length Polymorphism

Answer 3

• The fragment produced by cut of DNA by a restriction enzyme.
• The polymorphic variation is either having or not having a particular restriction site.
• When a site is lost, or less commonly gained, the enzyme cut at the next site, results in a longer, or shorter fragment.

Question 4

VNTR: Variable Number Tandem Repeat

Answer 4

• Tandem repeated sequences of variable length.
• Usually 10-100 bp for each repeated sequence.
• Also called a minisatellite in the DNA
• Useful in mapping, diagnosis and forensics.

Question 5

SSR: Simple Sequence Repeat

Answer 5

• Tandem repeated sequences usually 1-6 nucleotides long.
• More common than VNTR’s and now the most useful group of polymorphic markers for mapping, diagnosis and forensics.
• Also called microsatellites

Question 6

CNV’s: Copy Number Variants

Answer 6

• A deletion or duplication of a relatively large scale, typically 50 kb to 12 Mb.
• May or may not have an observable phenotype
• May be inherited and/or de novo