Transcript Genetic Nomenclature

Genetic Nomenclature
Wild-type allele: most frequent allele for a gene,
“the standard”, designated by superscript “+”
Mutant allele: allele that is not wild-type
Wild-type allele is not always dominant over a
mutant allele.
w
w+
white eyes (recessive)
wild-type (dominant)
Cy curly wings (dominant)
Cy+ wild-type (recessive)
Genetic Nomenclature
Allele designation is sometimes historical. The
name of a gene is often based on mutations for
the trait.
Cy is the gene for curly wings in Drosophila.
Wild-type phenotype is straight wings.
w is the gene for white eyes in Drosophila.
Wild-type phenotype is brick-red eyes.
Genetic Nomenclature
Aa is equivalent to A/a to describe a genotype.
“/” is used to show that “A” allele and “a” allele
are associated with homologous chromosomes “A” is on one homologue, “a” is on the other
homologue.
Aa Bb is equivalent to A/a ; B/b where “;” is
used to indicate that the two genes (locus A and
locus B) are on two different chromosomes
(different sets of homologues).