Lesson 4 Summary
Mendel
Peas
Phenotypes
Inheritance
Dominant & Recessive
Ratios 1
Ratios 2
Checkpoint
Human Health
Summary
In this lesson, we've learned about the difference between genotype and phenotype. We've also learned about the difference homozygous and heterozygous genotypes as well as dominant and recessive phenotypes. We also visualized Mendelian inheritance using Punnett squares.
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Let's put together everything we've learned into one final exercise:
1. Brachydactyly is a medical term which literally means "shortness of the fingers and toes."
This trait is inherited in a Mendelian fashion. Imaging you are in Medical school and interested in studying this recessive trait. You assemble a cohort of patients and sequence their genomes and find the following genotypes:
Genotype
AA
Aa
aa
Number of Patients
10
25
11
Calculate the following:
a. The number of patients with average-length fingers and toes?
b. The ratio of patients with average-length digits to those with brachydactyly?
Hint: You know now that in a Mendelian trait, homozygous dominant (AA) and heterozygous (Aa) genotype carriers will display the dominant phenotype, while homozygous recessive genotype carriers will display the recessive phenotype.