Biology Lab Report 7 “Independent Assortment & Dihybrid Cross”
Biology Lab Report 7
“Independent Assortment & Dihybrid Cross”
10-22-2013
Biology 202
Introduction: In genetics, when crossing a purebred white flower with a purple flower, we might expect its offspring to be a blend of both colors. Instead, we see that its offspring is purple as well. This is led to be by one trait being dominant over another trait. Gregor Mendel came up with a theory that each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results would be random. This law is known as the law of independent assortment.
In this laboratory experiment we will count and score the phenotypes of Drosophila melanogaster from a F2 generation of a dihybrid cross involving loci on the two major autosomes, chromosome two and three. A dihybrid cross is a cross between two parents that differ by two pairs of alleles. An example for this would be a parent from the F1 offspring who is (AABB) and the other parent being (aabb). Crossing those two parents to make offspring would be a dihybrid cross. A phenotype is an organism’s observable characteristics or traits while a genotype is a specific allelic combination for a certain gene or set of genes.
The reason why we will be using drosophila melanogaster or a “fruit fly” as an organism to study genetics and compare Medal’s laws to its offspring is because fruit flies can be produced in small vials and life cycles can be complete in about twelve days. It is inexpensive to maintain or breed these flies and take up very minimal space in a lab room. Also, it is easy and simple to observe our results and if needed, recreate the same experiment to check for inconsistencies. Using the chi-square formula we will calculate the goodness of fit to our expected ratio and our observed ratio when we determine and record our results. My null hypothesis for this lab experiment is that our ratio for the fruit flies will be at 9:3:3:1
“Independent Assortment & Dihybrid Cross”
10-22-2013
Biology 202
Introduction: In genetics, when crossing a purebred white flower with a purple flower, we might expect its offspring to be a blend of both colors. Instead, we see that its offspring is purple as well. This is led to be by one trait being dominant over another trait. Gregor Mendel came up with a theory that each member of a pair of homologous chromosomes separates independently of the members of other pairs so the results would be random. This law is known as the law of independent assortment.
In this laboratory experiment we will count and score the phenotypes of Drosophila melanogaster from a F2 generation of a dihybrid cross involving loci on the two major autosomes, chromosome two and three. A dihybrid cross is a cross between two parents that differ by two pairs of alleles. An example for this would be a parent from the F1 offspring who is (AABB) and the other parent being (aabb). Crossing those two parents to make offspring would be a dihybrid cross. A phenotype is an organism’s observable characteristics or traits while a genotype is a specific allelic combination for a certain gene or set of genes.
The reason why we will be using drosophila melanogaster or a “fruit fly” as an organism to study genetics and compare Medal’s laws to its offspring is because fruit flies can be produced in small vials and life cycles can be complete in about twelve days. It is inexpensive to maintain or breed these flies and take up very minimal space in a lab room. Also, it is easy and simple to observe our results and if needed, recreate the same experiment to check for inconsistencies. Using the chi-square formula we will calculate the goodness of fit to our expected ratio and our observed ratio when we determine and record our results. My null hypothesis for this lab experiment is that our ratio for the fruit flies will be at 9:3:3:1