2. Mendel's Laws of Inheritance
Monohybrid Cross
- Open QuestionThe following are F₂ results of two of Mendel's monohybrid crosses.(a) full pods 882constricted pods 299(b) violet flowers 705white flowers 224For each cross, state a null hypothesis to be tested using x² analysis. Calculate the x² value and determine the p value for both. Interpret the p values. Can the deviation in each case be attributed to chance or not? Which of the two crosses shows a greater amount of deviation?
- Open QuestionIn assessing data that fell into two phenotypic classes, a geneticist observed values of 250:150. She decided to perform a x² analysis by using the following two different null hypotheses: (a) the data fit a 3:1 ratio, and (b) the data fit a 1:1 ratio. Calculate the x² values for each hypothesis. What can be concluded about each hypothesis?
- Open Question
The seeds in bush bean pods are each the product of an independent fertilization event. Green seed color is dominant to white seed color in bush beans. If a heterozygous plant with green seeds self-fertilizes, what is the probability that 6 seeds in a single pod of the progeny plant will consist of
at least 1 white seed? - Open Question
The seeds in bush bean pods are each the product of an independent fertilization event. Green seed color is dominant to white seed color in bush beans. If a heterozygous plant with green seeds self-fertilizes, what is the probability that 6 seeds in a single pod of the progeny plant will consist of
all green seeds? - Open Question
The seeds in bush bean pods are each the product of an independent fertilization event. Green seed color is dominant to white seed color in bush beans. If a heterozygous plant with green seeds self-fertilizes, what is the probability that 6 seeds in a single pod of the progeny plant will consist of
3 green and 3 white seeds? - Open Question
Blue moon beans produce beans that are either the dominant color blue or the recessive color white. The bean pods for this species always contain four seeds each. If two heterozygous plants that each have the Bb genotype are crossed, what are the predicted frequencies of each of the five outcome classes for combinations of blue and white seeds in pods?
- Open Question
In the fruit fly Drosophila, a rudimentary wing called 'vestigial' and dark body color called 'ebony' are inherited as independently assorting genes and are recessive to their dominant counterparts full wing and gray body color. Dihybrid dominant-phenotype males and females are crossed, and 3200 progeny are produced. How many progeny flies are expected to be found in each phenotypic class?
- Open Question
A variety of pea plant called Blue Persian produces a tall plant with blue seeds. A second variety of pea plant called Spanish Dwarf produces a short plant with white seed. The two varieties are crossed, and the resulting seeds are collected. All of the seeds are white; and when planted, they produce all tall plants. These tall F₁ plants are allowed to self-fertilize. The results for seed color and plant stature in the F₂ generation are as follows:
F₂ Plant Phenotype Number
Blue seed, tall plant. 97
White seed, tall plant 270
Blue seed, short plant 33
White seed, short plant 100
TOTAL 500
Examine the data in the table by the chi-square test and determine whether they conform to expectations of the hypothesis. - Open Question
A variety of pea plant called Blue Persian produces a tall plant with blue seeds. A second variety of pea plant called Spanish Dwarf produces a short plant with white seed. The two varieties are crossed, and the resulting seeds are collected. All of the seeds are white; and when planted, they produce all tall plants. These tall F₁ plants are allowed to self-fertilize. The results for seed color and plant stature in the F₂ generation are as follows:
F₂ Plant Phenotype Number
Blue seed, tall plant. 97
White seed, tall plant 270
Blue seed, short plant 33
White seed, short plant 100
TOTAL 500
State the hypothesis being tested in this experiment. - Open Question
A variety of pea plant called Blue Persian produces a tall plant with blue seeds. A second variety of pea plant called Spanish Dwarf produces a short plant with white seed. The two varieties are crossed, and the resulting seeds are collected. All of the seeds are white; and when planted, they produce all tall plants. These tall F₁ plants are allowed to self-fertilize. The results for seed color and plant stature in the F₂ generation are as follows:
F₂ Plant Phenotype Number
Blue seed, tall plant. 97
White seed, tall plant 270
Blue seed, short plant 33
White seed, short plant 100
TOTAL 500
What is the expected distribution of phenotypes in the F₂ generation? - Open Question
Sweet yellow tomatoes with a pear shape bring a high price per basket to growers. Pear shape, yellow color, and terminal flower position are recessive traits produced by alleles f, r, and t, respectively. The dominant phenotypes for each trait—full shape, red color, and axial flower position—are the product of dominant alleles F, R, and T. A farmer has two pure-breeding tomato lines. One is full, yellow, terminal and the other is pear, red, axial. Design a breeding experiment that will produce a line of tomato that is pure-breeding for pear shape, yellow color, and axial flower position.
- Open Question
A cross between a spicy variety of Capsicum annum pepper and a sweet (nonspicy) variety produces progeny plants that all have spicy peppers. The are crossed, and among the plants are 56 that produce spicy peppers and 20 that produce sweet peppers. Dr. Ara B. Dopsis, an expert on pepper plants, discovers a gene he designates Pun1 that he believes is responsible for spicy versus sweet flavor of peppers. Dr. Dopsis proposes that a dominant allele P produces spicy peppers and that a recessive mutant allele p results in sweet peppers.
Assuming the proposal is correct, what proportion of the spicy F₂ pepper plants do you expect will be pure-breeding? Explain your answer. - Open Question
A cross between a spicy variety of Capsicum annum pepper and a sweet (nonspicy) variety produces progeny plants that all have spicy peppers. The are crossed, and among the plants are 56 that produce spicy peppers and 20 that produce sweet peppers. Dr. Ara B. Dopsis, an expert on pepper plants, discovers a gene he designates Pun1 that he believes is responsible for spicy versus sweet flavor of peppers. Dr. Dopsis proposes that a dominant allele P produces spicy peppers and that a recessive mutant allele p results in sweet peppers.
Are the data on the parental cross and the F₁ and F₂ consistent with the proposal made by Dr. Dopsis? Explain why or why not, using P and p to indicate probable genotypes of pepper plants. - Open Question
A pure-breeding fruit fly with the recessive mutation cut wing, caused by the homozygous cc genotype, is crossed to a pure-breeding fly with normal wings, genotype CC. Their progeny all have normal wings. F₁ flies are crossed, and the F₂ progeny have a 3:1 ratio of normal wing to cut wing. One male F₂ fly with normal wings is selected at random and mated to an F₂ female with normal wings. Using all possible genotypes of the F₂ flies selected for this cross, list all possible crosses between the two flies involved in this mating, and determine the probability of each possible outcome.