Phenotypes and Genotypes

Science, Grade 6


Table Of Contents: Phenotypes and Genotypes

1. What Are Genotypes and Phenotypes?
A genotype refers to the genetic makeup, or allele combinations, of an organism. A phenotype is the physical appearance of an organism.
2. Dominant and Recessive Phenotypes
If a dominant allele is present, then the phenotype will always be the dominant trait. A phenotype will be the recessive trait when two copies of the recessive allele are present.
3. BB x bb Cross
In this Punnett square, the parental cross results in offspring with only one allele combination. All the offspring would have the same genotype and phenotype.
4. BB x Bb Cross
The offspring in this Punnett square have two different genotypes, but all have the same phenotype.
5. Bb x Bb Cross
For this cross there are three possible genotypes and two possible phenotypes.
6. Probability for a Bb x Bb Cross
You could predict that 75% of the offspring would have black fur and 25% white fur. This is the same percentage that Mendel observed when crossing the F1 generations of pea plants.