notes: incomplete dominance phenotype is affected by · pdf filephenotype can depend on...
TRANSCRIPT
Notes: Incomplete Dominance Phenotype is affected by many different factors.
Phenotype can depend on interactions of alleles.
• In incomplete dominance, neither allele is completely dominant nor completely recessive.
– Heterozygous phenotype is a blend between the two homozygous phenotypes
– Homozygous parental phenotypes not seen in F1 offspring
Four o’clock plants aka Carnations
• Homozygous plants are either red (RR) or white (R’R’).
• Heterozygous (RR’) are pink.
This animation shows the cross between a black homozygous
dominant cat and a white homozygous recessive cat. This
results in a litter of all heterozygous gray cats.
• Codominant alleles will both be completely expressed.
– Codominant alleles are neither dominant nor recessive.
– The ABO blood types result from codominant alleles.
This animation shows the cross between a black homozygous recessive cat and a white homozygous dominant cat. This results in a heterozygous litter of black and white spotted kittens.
Codominance
• Multiple alleles: exists when genes have more than two alleles
– The ABO blood types result from multiple alleles that are codominant
Many genes may interact to produce one trait.
• Polygenic traits are produced by two or more genes.
Order of dominance: brown > green > blue.
• An epistatic gene can interfere with other genes by overshadowing them for a particular trait.
Labrador Retriever Genetics
• Black is dominant to chocolate B or b
• Yellow is recessive epistatic (when present, it blocks the
expression of the black and chocolate alleles) E or e
Phenotype Possible Genotypes
BBEE BbEE
BBEe BbEe
bbEE bbEe
Bbee Bbee
bbee
The environment interacts with genotype.
• Examples: • sex of sea turtles depends on both genes and temperature
• Phenotype is a combination of genotype and environment.