Connecting Concepts
Use Science Graphics
Seed coat was one trait that Mendel studied in pea plants. The coat, or covering, of the seed is either smooth or wrinkled. Suppose a researcher has two plants—one that makes smooth seeds and another that makes wrinkled seeds. The researcher crosses the wrinkled-seed plants and the smooth-seed plants, obtaining the following data. Use the data to answer questions 26–28.
Predict Mendel knew that the allele for smooth (R) seeds was dominant over the allele for wrinkled (r) seeds. If this cross was Rr × rr, what numbers would fill the middle column?
Analyze Data Are the observed numbers consistent with the hypothesis that the cross is Rr × rr? Explain your answer.
Draw Conclusions Are the data from this experiment alone sufficient to conclude that the allele for smooth seeds is dominant over the allele for wrinkled seeds? Why or why not?
Write About Science
Explain Write an explanation of dominant and recessive alleles that would be appropriate to give to an eighth-grade science class. You can assume that the eighth-grade students already know the meanings of gene and allele. (Hint: Use examples to make your explanation clear.)
Cause and Effect Explain why the alleles for reddish-orange eyes and miniature wings in Drosophila are usually inherited together. Describe the pattern of inheritance these alleles follow, and include the idea of gene linkage. (Hint: To organize your ideas, draw a cause-effect diagram that shows what happens to the two alleles during meiosis.)
Assess the
Explain why the gene pairs described by Mendel behave in a way that is consistent with the behavior of chromosomes during gamete formation, fertilization, and reproduction.
Analyzing Data
A researcher studying fruit flies finds a mutant fly with brown-colored eyes. Almost all fruit flies in nature have bright red eyes. When the researcher crosses the mutant fly with a normal red-eyed fly, all of the F1 offspring have red eyes. The researcher then crosses two of the F1 red-eyed flies and obtains the following results in the F2 generation.
Calculate What is the ratio of red-eyed flies to brown-eyed flies?
1 : 1
1 : 3
3 : 1
4 : 1
Draw Conclusions The allele for red eyes in fruit flies is
dominant over brown eyes.
recessive to brown eyes.
codominant with the brown-eyed gene.
a multiple allele with the brown-eyed gene and others.
Table of Contents
- Formulas and Equations
- Applying Formulas and Equations
- Mean, Median, and Mode
- Estimation
- Using Measurements in Calculations
- Effects of Measurement Errors
- Accuracy
- Precision
- Comparing Accuracy and Precision
- Significant Figures
- Calculating With Significant Figures
- Scientific Notation
- Calculating With Scientific Notation
- Dimensional Analysis
- Applying Dimensional Analysis