Questions 1–3
In dogs, one pair of alleles determines coat color (dark and albino). Another pair of
alleles determines hair length (short and long). Thus, each gamete will contain one of
the coat-color alleles, C or c, and one of the hair-length alleles, B or b. In repeated
crosses of a specific dark, short-haired dog with an albino, long-haired dog, all the
offspring were dark with short hair, as shown in cross I. However, in subsequent
crosses of another dark, short-haired dog with a dark, long-haired dog, the ratios
shown in cross II below were obtained.
Cross Parents Offspring
I. Dark, short hair x Albino, long hair All dark, short hair
II. Dark, short hair x Dark, long hair 3 dark, short hair
3 dark, long hair
1 albino, short hair
1 albino, long hair
1. In cross II, the genotype of the dark, short-haired parent is
(a) CcBb
(b) ccbb
(c) CCBB
(d) CCbb
A
2. Which of the following is probably the genotype of the dark, short-haired parent in cross I?
(a) CcBb
(b) ccbb
(c) CCBB
(d) CCbb
C
3. Which of the following correctly describes the relationship of the dark-coat-color
allele to the albino condition?
(a) It is dominant.
(b) It is recessive.
(c) It is codominant.
(d) It is a polygenic inheritance pattern.
A
4. The tiny blue-eyed Mary flower is often one of the first flowers seen in the spring in some regions of the United States. The flower is normally blue, but sometimes a white or pink flower variation is found.
The following data were obtained after several crosses.
Parents F1 F2
Blue × white Blue 196 blue, 63 white
Blue × pink Blue 149 blue, 52 pink
Pink × white Blue 226 blue, 98 white, 77 pink
(A) The appearance of blue in the F1 generation of the pink and white cross demonstrates that flower color is not an inherited trait but is determined by the environment.
(B) Flower color depends on stages of flower development, and young flowers are white, advancing to pink and then blue.
(C) Since the F1 and F2 phenotypes of the pink and white cross do not fit the expected genotypic and phenotypic ratios, blue-eyed. Mary must reproduce by vegetative propagation.
(D) Flower color is an inherited trait, and the F1 and F2 phenotypes of the flowers arising from the pink and white cross can best be explained by another gene product that influences the
phenotypic expression.
D
Example Free Response Question
1) In an investigation of fruit-fly behavior, a covered choice chamber is used to test whether the spatial distribution of flies is affected by the presence of a substance placed at one end of the chamber. To test the flies’ preference for glucose, 60 flies are introduced into the middle of the choice chamber at the insertion point indicated by the arrow in the figure above. A cotton ball soaked with a 10 percent glucose solution is placed at one end of the chamber, and a dry cotton ball with no solution is placed at the other end. The positions of flies are observed and recorded every minute for 10 minutes.
(a) Predict the distribution of flies in the chamber after 10 minutes and justify your prediction.
(b) Propose ONE specific improvement to each of the following parts of the experimental design and explain how the modifications will affect the experiment.
- Experimental control
- Environmental factors
(c) The experiment described above is repeated with ripe bananas at one end and unripe bananas at the other end. Once again the positions of the flies are observed and recorded every minute for 10 minutes. The positions of flies after 1 minute and after 10 minutes are shown in the table below.
DISTRIBUTION OF FLIES IN CHOICE CHAMBERTime (minutes) / Position in Choice Chamber
End with Ripe Banana / Middle / End with Unripe Banana
1 / 21 / 18 / 21
10 / 45 / 3 / 12
Perform a chi-square test on the data for the 10-minute time point in the banana experiment. Specify the null hypothesis that you are testing and enter the values from your calculations in the table below.
(d) Explain whether your hypothesis is supported by the chi-square test and justify your explanation.
(e) Briefly propose a model that describes how environmental cues affect the behavior of the flies in the choice chamber.
ANSWER
(a) Predict the distribution of flies in the chamber after 10 minutes and justify your prediction. (2 points maximum)
- 1 point for predicting the location of the flies in the choice chamber
- 1 point for justifying the prediction
(b) Propose ONE specific improvement to each of the following parts of the experimental design and explain how the modification will affect the experiment. (4 points maximum)
(c)
(d) Correct explanation with justification of why the stated null hypothesis is rejected or not rejected. Response must clarify each of the following:
degrees of freedom (df) = 2 and p = 0.05 (critical value = 5.99) OR
degrees of freedom (df) = 2 and p = 0.01 (critical value = 9.21
how the calculated test statistic compares to the selected critical value
whether the null hypothesis should be rejected
(e) Briefly propose a model that describes how environmental cues affect the behavior of the flies in the choice chamber. (1 point maximum)
Stimulus --> Response
Input --> (possible integration) --> Output