For three years, Gunther Schlager and Margaret Dickie estimated theforward and reverse mutation rates for five loci in mice that encodevarious aspects of coat color by examining more than 5 million mice forspontaneous mutations (G. Schlager and M. M. Dickie. 1966. Science151:205–206). They detected the following numbers of mutations at thedilute locus:                             Gametes examined                   Mutations detectedForwardmutations           260,675                                           5Reversemutations            583,360                                           2   Calculate the forward and reverse mutation rates at this locus. If thesemutations rates are representative of rates in natural populations of mice,what would the expected equilibrium frequency of dilute mutations be?

C. elegans can be viewed under a dissecting scope; their movement normally is sinusoidal, actually not unlike a snake slithering. Some C.elegans mutants have a mutations that cause them to roll instead of quickly move sinusoidally. You've collected two roller mutants, whose gene identity is currently unknown, but you temporarily give the names "A" and "B." You examine their phenotype in two different conditions. 15 degrees Celsius 26 degrees Celsius Wild type rol-? (A) sinusoidal movement rolls sinusoidal movement rolls Which C. elegans strain is temperature-sensitive? A Which temperature is the permissive condition? 26 degrees rol-? (B) sinusoidal movement rolls

A scientist investigating the genome of two related individuals observes a difference of a few nucleotides in one individual compared to the other. The nucleotide differences are in a region of noncoding DNA on chromosome 1. Would these differences be considered a mutation? Why or why not? Yes, the difference in nucleotide sequences between the individuals is a mutation because it will affect the phenotype of the two individuals. Yes, any heritable variation in the nucleotide sequence is considered a mutation, even if that variation is in a noncoding region of DNA. Not enough information was provided to determine if this nucleotide difference is a mutation because the effect on phenotype is unknown. No, the change in nucleotide sequence doesn't appear in a coding region of the DNA and so can't be a mutation.

Cyndi grows thousands of B. rapa plants from seed and carefully watches for any unusual plants that might be a new mutation. She has been watching a small seedling whose leaves continue to develop, but the stem is not elongating. The result is a cluster, or rosette, of leaves sitting just above the soil surface. After 15 days the plant is beginning to produce flowers but is still a rosette. Cyndi is encouraged and hypothesizes that rosetteis a recessive mutation.  -Describe the first cross she should make and the predicted results. Because B. rapa is an annual plant, the one rosette individual dies. Cyndi would like to continue her study of this mutation, but all od the offspring from her original cross were normal. There are no more plants with the rosette mutation.  -What can Cyndi do to continue her investigation of rosette? What would be the results of these "next steps"? -What results would you expect if Cyndi crosses her new generation of rosette plants with a known heterozygous…

William Jeffrey and his colleagues crossed surface-dwelling Mexican tetras that had fully developed eyes with cave-dwelling blind Mexican tetras. The progeny from this cross had uniformly small eyes compared with those of surface fish (Y. Yamamoto, D. W. Stock, and W. R. Jeffrey. 2004. Nature 431:844–847). What prediction can you make about the expression of shh in these progeny at the embryonic stage relative to its expression in embryonic surface fish?