EXAM 3 Extensions of Mendel Notes Flashcards
(26 cards)
What does the recessive allele do in a simple dominant/recessive relationship?
Does not affect the phenotype of the heterozygote
What are the two possible explanations for the wild-type phenotype of the heterozygote?
- 50% of normal protein is enough for function
- Heterozygote produces more than 50% of functional protein
What is a dominant mutant?
Much less common than recessive mutants
What are the three explanations for most dominant mutations?
- Gain-of-function
- Dominant-negative
- Haloinsufficiency
Define incomplete dominance.
Heterozygote exhibits a phenotype intermediate between corresponding homozygotes
What are essential genes?
Absolutely required for survival
What is a lethal allele?
Has the potential to cause the death of an organism
What are conditional lethal genes?
May kill an organism only under certain environmental conditions
Give an example of a temperature-sensitive conditional lethal gene.
A developing Drosophila larva may be killed at 30 degrees C but will survive at 22 degrees C
What are semilethal alleles?
Kill some individuals in a population, not all
What is an example of multiple alleles in genetics?
Coat color in rabbits with 4 different alleles
What are the four alleles for coat color in rabbits?
- C (full coat color)
- c^ch (chinchilla pattern)
- c^h (himalayan pattern)
- c (albino)
What is the ABO blood group determined by?
Type of antigen present on the surface of red blood cells
What are the three different types of antigens found on red blood cells?
- Antigen A (I^A)
- Antigen B (I^B)
- Antigen O (i)
What is overdominance?
Heterozygote is more vigorous than both corresponding homozygotes
What is an example of overdominance?
Sickle cell anemia
What are the two alleles for hemoglobin in sickle cell anemia?
- Hb^A (normal hemoglobin)
- Hb^S (abnormal hemoglobin)
What is incomplete penetrance?
Dominant allele is not expressed in a heterozygote individual
What does expressivity refer to?
Degree to which a trait is expressed
What is pleiotropy?
Multiple effects of a single gene on the phenotype of an organism
What is gene interaction?
Occurs when two or more different genes influence the outcome of a single trait
What does epistasis describe?
A gene can mask the phenotypic effects of another gene
What is sex-influenced trait?
Trait where an allele is dominant in one sex but recessive in the opposite sex
Give an example of a sex-influenced trait.
Pattern baldness in humans
