BIOL 234 - One gene three alleles worksheet(1)

BIOL 234 - One gene three alleles worksheet(1) - BIOL 234...

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BIOL 234 Summer 2017 Genetic analysis with one gene, three alleles (Yes, you are responsible for knowing this, and yes, this could be on an exam) Good news: with diploid organisms, and independent assortment (genes of interest on separate chromosomes), there are only so many possible F1/F2 ratios that we can observe. Individuals are still either homozygous or heterozygous, and alleles are still dominant/co-dominant/recessive (it depends): there are just more alleles to choose from. Activity 1 – blood types Consider the example of blood type, with which you are probably familiar. The ABO blood groups are determined by the presence or absence of sugar molecules on the surface of red blood cells. These sugars are called antigens, which means that they are recognized by cells of the immune system. There are 3 possible alleles: I A (antigen type A) I B (antigen type B) i (no antigen produced – type O) Write out all of the possible genotypes that could result in each blood type (A, B, AB, and O). What are the dominance relationships between the alleles? Now try some crosses. In cases where you can’t tell whether an individual is true-breeding, leave one allele blank at first. Then, fill in the blank with possible options for the second allele. Predict F1 phenotypic ratios for each cross, including multiple possible outcomes in cases where you don’t know if an individual is true-breeding. Cross 1: type AB x type O Cross 2: type B x type A Cross 3: type O x type A Cross 4: type AB x type B
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Activity 2 – design your own problem Try this activity – it will help you to understand why you see certain ratios in the F1/F2, given certain parents. 1. Consider how many genes are involved, and how many alleles of each gene (e.g. 2 genes, one with 2 alleles, and the other with 3 alleles).
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