Topic Question 5.4-6

An experiment was performed to determine the mode of inheritance of two mouse genes, one for fur color and one for fur length. It is known that black fur (BB) is dominant over white fur (bb) and that long fur (LL) is dominant over short fur (ll). To determine how the genes are inherited, a cross was performed between two true-breeding mice, one with long black fur and one with short white fur. Their progeny, the F1F1 generation, all had long black fur. Five F1F1 male-female pairs were then crossed with one another. The F2F2 generation phenotypes for each cross are shown in Table·1. Which of the following is the mean number per cross of F2F2 generation offspring that are the result of crossing over?

2.2

Pigeons demonstrate ZWZW sex determination, such that a ZZZZ genotype produces a male and a ZWZW genotype produces a female. The gene for feather color is located on the ZZ chromosome, and the red allele is dominant over the brown allele. Three crosses between brown male pigeons and red female pigeons were performed, and the results are shown below. Which of the following is the mean number of male offspring produced by the three crosses?

9

A student carries out a genetics experiment with fruit flies to investigate the inheritance pattern of the white eye trait. The student crosses a homozygous white-eyed female with a wild-type male and records observations about the flies in the F1 generation. The student plans to use the F1 data to perform a chi-square goodness-of-fit test for a model based on an X-linked recessive pattern of inheritance. The student will use one degree of freedom and a significance level of p=0.05. The setup for the student's chi-square goodness-of-fit test is presented in Table 1. The student calculates a chi-square value of 0.36. Which of the following statements best completes the student's chi-square goodness-of-fit test?

The critical value is 3.84, and the student cannot reject the null hypothesis. The critical value is 3.84, and the student cannot reject the null hypothesis.

In fruit flies, sepia eyes and ebony body are traits that display autosomal recessive patterns of inheritance. To investigate whether the traits are genetically linked, students cross wild-type flies with a line of flies that have sepia eyes and ebony bodies. The students observe that all the flies in the F1F1 generation have normal eyes and normal bodies. The students allow the flies in the F1F1 generation to mate and produce an F2F2 generation. The students then record observations for the flies in the F2F2 generation and use the data to perform a chi-square goodness-of-fit test for a model of independent assortment. The setup for the chi-square goodness-of-fit test is presented in Table 1. The students calculate a chi-squared value of 92.86 and compare it with a critical value of 7.82. Which of the following best completes the chi-square goodness-of-fit test?

The null hypothesis can be rejected, and the students should conclude that the data may have resulted from genetic linkage.

A gene that influences coat color in domestic cats is located on the XX chromosome. A female cat that is heterozygous for the gene (XBXOXBXO) has a calico-colored coat. In a genetics experiment, researchers mate a calico-colored female cat (XBXOXBXO) with an orange-colored male cat (XOYXOY) to produce an F1F1 generation. The researchers record observations for the cats in the F1F1 generation and plan to use the data to perform a chi-square goodness-of-fit test for a model of XX-linked inheritance. The data for the chi-square goodness-of-fit test are presented in Table 1. The researchers calculate a chi-square value of 4.6 and choose a significance level of p=0.05p=0.05. Which of the following statements best completes the chi-square goodness-of-fit test?

The null hypothesis cannot be rejected because the chi-square value is less than the critical value.

In order to determine the effects of age on the accumulation of mitochondrial mutations, mitochondrial DNADNA samples from young mice (3 months) and old mice (30 months) were observed for mutations. Which of the following is a correct analysis of this data set?

There is an increase in the mean number of mutations for the two age groups of 9.2 mutations per 106106 base pairs. This is more critical in female mammals since mitochondria are maternally inherited.