EPISTASIS Flashcards
■ Interaction of nonallelic genes in the formation of the phenotype
Epistasis
__________ is a form of gene interaction in which one gene masks the phenotypic expression of another.
Epistasis
■The alleles that are masking the effect are called epistatic alleles
Epistatic alleles
The alleles whose effect is being masked are called the hypostatic alleles.
hypostatic alleles
Epistasis can be described as either ______ or ________
recessive epistasis or dominant epistasis.
Occurs when the dominant allele of one gene masks the effects of either allele of the second gene.
Dominant epistasis
__________color is controlled by two genes
Squash fruit color
__________ gene that can affect the expression of another gene
EPISTATIC
Also known as dominant inhibitory epistasis
DOMINANT RECESSIVE INTERACTION
Traits that occur in distinct categories
DISCONTINUOUS
Distribution of phenotypes in the population varies along a continuum
CONTINUOUS
Is an o-methyled anthocyanin responsible for the blue pigments of primula polyanthus plant
MALDVIN
Dominant recessive example is
MALDVIN IN PRIMULA FLOWERS
More than two alleles and genes control the expression of trait
POLYGENIC INHERITANCE
Also known as Duplicate Gene Action
DUPLICATE DOMINANT EPISTASIS
Also known as complementary Gene action
Duplicate recessive epistasis
Dominant alleles complement each other
DUPLICATE RECESSIVE EPISTASIS
Dominant epistasis
Ratio 12:3:1
Recessive epistasis
Ratio 9:4:3
● If a dominant allele of both gene loci produces
the same phenotype without cumulative effec
DUPLICATE DOMINANT EPISTASIS
Both the dominant non allelic alleles, when
present together, give a new phenotype, but
when allowed to express independently, they
give their own phenotypic expression separately
DUPLICATE GENES WITH CUMULATIVE EFFECTS
If both gene loci have homozygous recessive
alleles and both of them produce identical
phenotype.
DUPLICATE RECESSIVE EPISTASIS
DUPLICATE GENES WITH CUMULATIVE EFFECTS
● The ratio will be 9:6:1
The dominant allele, either in homozygous or
heterozygous condition, of one gene and the
homozygous recessive of other gene produce
the same phenotype
● Ratio 13:3
The phenomenon in which a single gene
conditions affects several different phenotypical
traits
PLEIOTROPY
a is an abnormality
in the expression of a single mutated
each BB gene which produces
numerous consequences throughout the
body
SICKLE CELL ANEMIA
It is caused by a defect in the
phenylalanine hydroxylase enzyme. So
the gene responsible for that is mutated
● Phenylketonuria
○ Lack of thyroxine from birth
○ Or before birth
○ Could be lack of thyroid gland
○ Or lack of iodine in mother
○ Severe and irreparable mental defects
○ Stunted growth
○ Reduced growth and function of many
organs
CRETINISM
○ genes with at least one allele that one
present in the genotype of an individual,
causes death.
○ it can be dominant or recessive lethal
● Lethal Genes
○ The perfect example is the Huntingdon’s
disease. If the father is recessive to
Huntington’s disease and the mother is
heterozygous you will produce 50
percent affected child and 50 percent
normal child.
● Dominant Lethal Genes
Low levels of thyroid hormone in early years life
CRETINISM
Dwarfism
ACHONDROPLASIA
Example of Recessive lethal genes
Manx cats tail less
CFTR means
Cystic Fibrosis Transmembrane Receptor
CFTR gene mutation
Cystic Fibrosis
