Gregor Mendel did his research with pea plants that have simple dominant/recessive characteristics. He used capital letters to represent the dominant “factor” (gene) for a trait, and the same letter stated in lower-case to represent the recessive “factor” for the same trait. The possible patterns of inheritance his research revealed for such simple dominant v. recessive traits were: AA, aa or Aa. As research progressed over the years, one question people kept asking was, “Why don’t the recessive traits disappear over generations of breeding within a given population?”
If one allele for a characteristic is dominant, and another allele for the same body feature is recessive, then you would expect that the recessive gene would disappear from a given population over time. In fact, recessives do not vanish from most normal populations.
In 1908 Godfrey Hardy and Wilhelm Weinberg proposed a mathematical explanation for the stability of successive generations of populations, specifically populations that might be in a state of genetic equilibrium.
The Hardy-Weinberg Principle represents an ideal situation that probably never occurs in the natural world, but it allows us to study the expression of traits mathematically it also proves the existence of natural selection within a population.
|Hardy Weinberg Equation = p2 + 2pq + q2 = 1
|Frequency of AA = p2
||Frequency of Aa = 2pq
||Frequency of aa = q2
You will work in teams of two for this lab. Each person will have a bag of “alleles”. Dark beans will be used to represent the dominant allele (“A”), and light beans will represent the recessive allele (“a”). One person will be “male”; the other will be “female”. Each will have the same numbers and types of “alleles” in his/her bag.
Each parent will select one allele from his/her bag and place it next to a selection made by the other person. This pair represent alleles donate by the two parents. You will perform 60 of these “matings” and then review the results.
How often was the F1 “AA”, how often “Aa” and how often “aa”? Also – each time a dominant allele was donated to form an “Aa” offspring, which parent donated the dominant: the male or the female?