|
.
|
- Biologists can use Punnett squares to dettermine the probability that a specific trait will be displayed by an offspring.
- Geneticists use capital letters to refer to dominant alleles, and lowercase letters to refer to recessive alleles.
- Each trait in an organism has three possiible genotypes, TT, tt, or Tt
- TT and tt are homozygous traits. (True-brreeds)
- Tt is a heterozygous trait.
- Mendels' original 3: 1 ratio can be conveerted into percent probability:
1/4 = 25% Recessive Trait
3/4 = 75% Dominant Trait
- The genotypes can also be determined
aas 1 : 2 : 1 or
1/4 = 25% TT
2/4 = 50% Tt
1/4 = 25% tt
- A monohybrid cross is used to determine tthe probability of one specific trait, but a dihybrid cross can be used to determine the probability of two traits.
- - Not all traits are simply dominant or recessive:
- ) Incomplete Dominance- Heterozygous trait (Tt) is displayed differently from both dominant and recessive traits
- ) Codominance- there is no recessive trait so that two traits are displayed at the same time.
- ) Multiple Alleles- there are more than just two genes for a trait.
- ) Continuous Variation- Physical traits exhibit a wide variety of possibilities
- ) Environmental Influences- Physical traits may be able to change to better suit the environment.
|
