Honor System


Course Topics


Homework Assignment - Gene and Mutations

Points: 100 points total

Use complete sentences in all of your answers where appropriate. If you are stumped by a problem, explain as much as you can to get partial credit.

1. Write an essay that describes mutations. Your essay should: a) contrast spontaneous and induced mutations; b) briefly describe physical, chemical and biological methods of developing new mutations; c) describe different types of mutations; and d) explain the importance of mutations for genetic research. You will need between 10 and 15 sentences to answer this question sufficiently. This question is worth 30 points.

2. Your research group is interested in color expression in the flowers of the species "color-me-blue". You treated seeds of the wild type blue flowered plant with ethyl methane sulfanate and obtained five white-flowered, pure-breeding mutants. Each of these mutants were first crossed to the wild type plant, and the flowers of all of the F1 progeny were blue. You next crossed all of the mutants, and the results are presented in the table below. From these results, describe the genetic relationship between the mutants. If the F1 progeny from the cross of mutants 4 and 5 were selfed, what ratio would you expect to observe in the F2 generation. (30 points)

Mutant Cross F1 Phenotype
1 x 2 Blue
1 x 3 White
1 x 4 Blue
1 x 5 White
2 x 3 Blue
2 x 4 Blue
2 x 5 Blue
3 x 4 Blue
3 x 5 White
4 x 5 Blue

3. As a conservation geneticist, you are interested in defense mechanisms in nature. The self-pollinated plant species called "maroon bells" inhabits the banks of Snowmass Creek in Colorado. Although this is normally a hardy plant, this season you noticed two groups of plants that are susceptible to the pathogen "eat me alive." This is unusual because the species has always shown resistance to the pathogen. You took seeds of these plants into the lab (being very careful not to mix seeds from different mutants) and created two pure-lines. Next you performed a series of crosses. Those results are shown in the table below. Develop a complete genetic explanation for all of the results. (Note: Recipricol crosses gave the same ratios.) (40 points)

Cross F1 Phenotype F2 Phenotypic Ratio
Mutant 1 x Mutant 2 Susceptible 13 susceptible
3 resistant
Mutant 1 x Wild type Susceptible 3 susceptible
1 resistant
Mutant 2 x Wild type Resistant 3 resistant
1 susceptible