Solving Mendelian Genetics Problems
Genetics is a science that involves symbols (A, b, p), structures (chromosomes, ribosomes) and processes (meiosis, replication, translation) which interact in a variety of ways. Because of this interaction (both in time and space), genetics should not be approached as a topic filled with facts that should be memorized. You will find your study of genetics much more rewarding if you strive to understand not only how the symbols, structures and processes work but the interrelationships between them. Please remember that it takes time, work and patience to understand genetics.
I suggest going through the following steps when solving genetics problems: (1) analyze each problem carefully to determine what information is provided and what information is asked for; (2) translate the words of the problem into symbols, and (3) solve the problem using logic.
The most basic problems involving Mendelian inheritance usually give some information about the parental genotype (P) and ask you to come to conclusions about the genotypes or phenotypes of the F1 or F2 generations, The solution uses several steps:
1. Carefully read the problem and establish the genotype of each parent, assigning letter symbols if necessary.
2. Based on their genotypes, determine what types of gametes can be formed by each parent.
3. Unite the gametes from the parents in all combinations. Use a Punnett square if necessary. The Punnett square automatically gives you all possible genotypes and their expected ratios for the F1 generation.
4. If necessary, use all combinations of F1 individuals as parents of the F2, and repeat steps 2 and 3 to derive the genotypes and phenotypes of the F2 generation.
When working genetics problems in this course, always assume that members of the P generation are homozygous, unless the information given, or the data provided, indicates otherwise.