Consequences of Genetic Variation

Gene

Allele

sequence variant of a gene; different alleles code for different information

a section (locus) of DNA that encodes information

Single Nucleotide Polymorphisms

Allelic Variation in Coding Regions of Genes

Indels and Frameshift Mutations

Copy Number Variants

change to a single base-pair in DNA

Indels: Insertions or deletions of basepairs

Frameshift: if the indels are not in multiples of 3

changes to # of copies of a gene or cluster of genes (can be duplications or deletions

Silent

Missense

Nonsense

Substitution DOES NOT change the amino acid

Substitution CHANGES amino acid

Substitution creates a STOP codon

changes the reading frame of translation

Dominant Alleles

Recessive Alleles

determines phenotype even if only one copy is present

determines phenotype only when two copies are present

Polymorphic Genes

Codominance

Incomplete dominance

Environmental Influences on Phenotype

example: flower color

acidic soil = blue hydrangea

basic soil= pink hydrangea

There are more than two alleles in a population

example: hair color

Multigenic Traits

traits influenced by more than one gene

example: skin color

Epistasis

traits influenced by more than one gene

When one gene controls other genes

most transcription factors are epistatic

ex: albinsim

overrides other pigment information

labrador example

both alleles are simultaneously expressed in the heterozygote

example: blood type

the phenotype of the organism is a blend between the phenotypes of its parents

example: parent flowers are red and white, offspring has pink petals

Genetic Variation: complicated relationships between alleles and genes

Terms:

example: amylase gene