Monohybrid cross and the Punnett square
A monohybrid cross and the Punnett square
In order to solve a monohybrid cross using a Punnett square let's review some basic genetic vocabulary.
Trait A characteristic that can be passed from one generation to another.
An example of a trait would be eye color.
An allele is a different form of the same trait.
Having different eye color would be an example of an allele.
Alleles are described as either dominant or recessive depending on their associated traits
When solving Punnett squares keep the following in mind
dominant allele + dominant allele = dominant phenotype ( homozygous because both alleles are the same)
dominant allele + recessive allele = dominant phenotype ( heterozygous two different alleles)
recessive allele + recessive allele = recessive phenotype ( homozygous )
A dominant trait is always written with a capital letter.
Recessive is written with a lower case
The steps for setting up a Punnett square are as follows.
Draw the Punnett Square box.
Write the genotype of the parents on the top and on the side of the Punnett square.
Fill in the boxes
Determine the percentages of phenotypes which is the physical expression of the trait
Each box of the Punnett square is 25 %
Two red heterozygous flowers are crossed. For this flower type, the color can be white or red. Use a Punnett square to determine the probability of one of their offspring having a white color.
Step 1 Draw the Punnett square
Step 2 Write the genotype of the parents. I need to look for information in the problem.
Both flowers are heterozygous for red color.
I will use the letter T
Heterozygous is written capital letter lower case.
A heterozygous genotype is always a dominant trait.
So both parents are written Tt because they are heterozygous
Step 3 Fill in the boxes
Now let’s see what the chances are a white flower will appear.
