GENETICS - BIOL 7            Homework due Oct 26, 2006

All homework must be typed - printed by machine.  See general class instructions regarding homework.  Assignments may be emailed; if you email, please do NOT also turn in hard copy.

1.  Explain ABO +/- blood group types and use them to illustrate the exceptions to Mendel: codominance, epistasis, multiple alleles, multiple genes.  Are there any components of this system that follow Mendelian “rules”?  If so, explain.

2.  Explain the difference between incomplete dominance and co-dominance.  What experiments or investigations would generate data distinguishing these two explanations for red flowering plant x white flowering plant –> all pink flowering plants.  F2 yielded red : pink : white = 1:2:1.

3.  An alternative explanation for red x white –> pink; F2 a mixture of red, pink, and white offspring could entail 2 genes.  Describe such a system, and predict the ratio of red : pink : white offspring in the F2 according to your model.

4.  Consider biochemical pathways that convert a substrate to an intermediate to a final product, using a distinct enzyme to catalyze the reactions; imagine systems in which the enzyme is the product of a single gene.  For each of the following, clearly state the predicted phenotypic ratios for the appropriate dihybrid cross to investigate the two enzymes and the presumed pathway with the predicted genotypes arranged by the phenotypes they cause.

     a.  The phenotypes for accumulated substrate, intermediate, and product can all be distinguished.

     b.  The phenotypes for accumulated substrate and accumulated product can NOT be distinguished; accumulated intermediate is distinct.

     c.  The phenotypes for accumulated substrate and accumulated intermediate can NOT be distinguished; accumulated product is distinct.

     d.  another distinct pathway of your own choosing – DO NOT REPEAT!