Chapter 5: Mods of Basic Principles Flashcards
What is incomplete dominance?
Only one allele is expressed; the other allele is nonfunctional. Mixing of two
What is codominance
Heterozygote displace phenotype of both homozygotes
- Red blood cells
Why is dominance tricky?
At molecular level heterozygotes have both normal and mutant Cl channels (codominance)
Only homozygous recessive individuals show symptoms of disorder (complete dominance)
It has been suggested that carrier have mild symptoms and less susceptible to cholera (overdominance)
What is penetrance?
The percentage of individuals having a particular genotype that express the expected phenotype
What is expressivity
The degree to which a character is expressed
What is incomplete penetrance
Genotype does not always produce the expected phenotype
such as polydactyly
What is variable expressivity
Variation in the degree to which a trait is expressed
What cause incomplete/variable expressivity
Environment (temp)
Effects of other genes
Concentration threshold where heterozygotes are right at the threshold
What are lethal alleles?
Cause death at an early stage of development, and so some genotypes may not appear among the progeny. This makes them recessive
What is gene interaction
Effects of genes at one locus depend on the presence of genes at another locus
Such as bell pepper
What is epistasis
One gene masks the effect of another gene
What is the difference between epistatic gene and hypostatic gene?
Epistatic: gene that does the masking
Hypostatic gene: gene whose effect is masked
What is the Bombay phenotype?
H locus is epistatic to the ABO locus
ABO locus determines which sugar, if any, get added onto a glycoprotein
H locus encodes an enzyme that adds a sugar that is necessary for adding on the terminal sugar that determines the phenotype of the ABO locus
