Investigating Independent Assortment

In this post, we are going to discuss independent assortment. To give you a basic understanding, independent assortment is where individual heredity factors assort themselves independently during gamete production. This gives different traits equal opportunity of occurring together.

To begin, we are going to determine which allele combinations are possible in two or three trait crosses. To accomplish this, I used http://www.sumanasinc.com/webcontent/animations/content/independentassortment.html as a source. Based on the animation, we are able to determine that if the dipoid cell aligns its chromosomes in all ways possible,  the result will consist of equal amounts of sY, sy, Sy, and SY genotypes. We are also able to determine that the alleles of the S and Y genes assort themselves independently.

Next, we are going to answer some questions surrounding the topic of independent assortment.  To do this, we are going to use http://www.biology.arizona.edu/mendelian_genetics/problem_sets/dihybrid_cross/dihybrid_cross.html as a source for information.

1. What type of gametes will be produced by a plant of genotype AaBb?

    A plant with the genotype AaBb will produce AB, Ab, aB, and ab gametes, due to the fact that if you go through all possibilities this is the only combination that can be achieved.

2. What type of gametes will be produced by a plant of genotype aabb?

A plant with the genotype aabb will produce ab gametes, due to the fact that there are no dominant genes present.

3. List all the genotypes you would find among the offspring of an AaBb x aabb test cross.

    A cross between the genotype AaBb and the genotype aabb will produce AaBb, Aabb, aaBb, and aabb genotypes. These are all the combinations possible in a cross between AaBb and aabb types.

4. What is the expected phenotypic ratio of the offspring of an AaBb x aabb test cross? Show the punnett square you would use for predicting the outcomes.

   A cross between the genotype AaBb and the genotype aabb will produce AaBb, Aabb, aaBb, and aabb genotypes. The punnett square used to determine these genotypes is displayed below.

The phenotype created would be shown through the dominant alleles in the combination.

5.What are the genotypic and phenotypic ratios from a AaBb x Aabb mating?

   A cross between the genotype AaBb and the genotype aabb will produce a phenotypic ratio of 1:1:1:1 because there is only one occurrence of each genotype. The ratio is also 1:1:1:1 for the genotypic ratio.

6. List all possible gametes from a trihybrid individual whose genotype is RrSsTt.
   A trihybrid individual with the genotype RrSsTt will produce the following gametes: RST, RSt, RsT, Rst, rST, rsT, rSt,  and rst.