Vocabulary
Genes
A trait that an organism possesses
Vocabulary
Alleles
A version of a trait
There are two alleles in each organism.
Vocabulary
Dominant
An allele that overrules any other recessive alleles
Part of an organism’s phenotype unless there are no dominant alleles
Vocabulary
Recessive
An allele that is overruled by any other dominant alleles
Only seen in a phenotype if a recessive homozygous allele is present
Vocabulary
Genotype
The alleles in an organism
Example: AA, Aa, or aa
Vocabulary
Phenotype
The physical appearance of a gene
Example: A or a
Vocabulary
Homozygous Allele Combinations
When two of the same type of an allele are present in a gene.
Dominant or recessive homozygous allele combinations can exist
Example: AA or aa
Vocabulary
Heterozygous Allele Combinations
When two different types of an allele are present
Most commonly one dominant allele and one recessive allele
Example: Aa
Questions
What allele combinations show the dominant phenotype?
AA or Aa
A combination including dominant allele(s) will be a dominant phenotype
Questions
What allele combinations show the recessive phenotype?
aa
A combination with no dominant allele(s) will have a recessive phenotype
Questions
What is the molecule that contains information for traits?
Alleles
Alleles contain genes, which contain the information for traits.
Questions
What are Punnett squares and why are they useful?
Punnett squares are 2 by 2 grids that theoretically contain both parent’s genotypes and all of their possible offspring’s genotypes. They can be useful becuase they can be a easy way to visually show and organize experiments and what their results would be in addition to assisting the calculation of how probable each outcome/result is.
Questions
How can you tell if a trait is dominant, recessive, or co-dominant? What crosses would you have to do to figure this out?
TRIAL #1: Cross a phenotype with another of the same phenotype:
* If a new trait appears, the original genotypes are heterozygous (Aa). The new trait is recessive (aa).
* If no new traits appear consistently, then the genotypes are homozygous (AA or aa) or they are co-dominant. Try trial #2 with the original phenotype and a new, different phenotype to further determine the type of trait.
TRIAL #2: Cross a phenotype with a different phenotype:
* If both of the original traits are expressed at the same time in the same organism, then they are co-dominant traits.
* If both of the original phenotypes are expressed in different organisms in the results, then one of the original genotypes is heterozygous (Aa) and one of the organisms is recessive (aa). Or, they are both co-dominant. Try trial #1 twice: one for one original phenotype and one for the other original phenotype. If one of them turns out to be heterozygous, then the other is recessive. If not, you might have to try trial #2 again, but with a different copy of the same phenotype.
* If only one of the phenotypes result consistently, then the genotype that is resulting is a heterozygous (Aa) and the parent phenotype that matches the resulting phenotype has a uniformly dominant (AA) genotype. The parent’s genotype that doesn’t match the resulting phenotype is recessive (aa).
