2. Mendel's Laws of Inheritance

Monohybrid Cross

Open Question
In a type of parakeet known as a 'budgie,' feather color is controlled by two genes. A yellow pigment is synthesized under the control of a dominant allele Y. Budgies that are homozygous for the recessive y allele do not synthesize yellow pigment. At an independently assorting gene, the dominant allele B directs synthesis of a blue pigment. Recessive homozygotes with the bb genotype do not produce blue pigment. Budgies that produce both yellow and blue pigments have green feathers; those that produce only yellow pigment or only blue pigment have yellow or blue feathers, respectively; and budgies that produce neither pigment are white (albino).List the genotypes for green, yellow, blue, and albino budgies
Open Question
Predict the results of a cross between ascospores from a segregational petite strain and a neutral petite strain. Indicate the phenotype of the zygote and the ascospores it may subsequently produce.
Open Question
In a cross of Lymnaea, the snail contributing the eggs was dextral but of unknown genotype. Both the genotype and the phenotype of the other snail are unknown. All F₁ offspring exhibited dextral coiling. Ten of the F₁ snails were allowed to undergo self-fertilization. One-half produced only dextrally coiled offspring, whereas the other half produced only sinistrally coiled offspring. What were the genotypes of the original parents?
Open Question
In the datura plant, purple flower color is controlled by a dominant allele P. White flowers are found in plants homozygous for the recessive allele p. Suppose that a purple-flowered datura plant with an unknown genotype is self-fertilized and that its progeny are 28 purple-flowered plants and 10 white-flowered plants.

If one of the purple-flowered progeny plants is selected at random and self-fertilized, what is the probability it will breed true?
Open Question
In the datura plant, purple flower color is controlled by a dominant allele P. White flowers are found in plants homozygous for the recessive allele p. Suppose that a purple-flowered datura plant with an unknown genotype is self-fertilized and that its progeny are 28 purple-flowered plants and 10 white-flowered plants.

Use the results of the self-fertilization to determine the genotype of the original purple-flowered plant.
Open Question
In chickens, a condition referred to as 'creeper' exists whereby the bird has very short legs and wings and appears to be creeping when it walks. If creepers are bred to normal chickens, one-half of the offspring are normal and one-half are creepers. Creepers never breed true. If bred together, they yield two-thirds creepers and one-third normal. Propose an explanation for the inheritance of this condition.
Open Question
In a cross between a black and a white guinea pig, all members of the F₁ generation are black. The F₂ generation is made up of approximately 3/4 black and 1/4 white guinea pigs.Two different matings were made between black members of the F₂ generation, with the following results.Diagram each of the crosses.Cross Offspring _Cross 1 All blackCross 2 3/4 black, 1/4 white
Open Question
In a cross between a black and a white guinea pig, all members of the F₁ generation are black. The F₂ generation is made up of approximately 3/4 black and 1/4 white guinea pigs.What will the offspring be like if two F₂ white guinea pigs are mated?
Open Question
In a cross between a black and a white guinea pig, all members of the F₁ generation are black. The F₂ generation is made up of approximately 3/4 black and 1/4 white guinea pigs.Diagram this cross, showing the genotypes and phenotypes.
Open Question
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.

Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard

Propose two different genetic crosses that would allow you to determine the genotype of one mottled frog from the F₂ generation.
Open Question
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.

Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard

In the F₂ progeny from both crosses, what proportion is expected to be homozygous? What proportion is expected to be heterozygous?
Open Question
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.

Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard

Compare and contrast the results of the reciprocal crosses in the context of autosomal gene inheritance.
Open Question
The dorsal pigment pattern of frogs can be either 'leopard' (white pigment between dark spots) or 'mottled' (pigment between spots appears mottled). The trait is controlled by an autosomal gene. Males and females are selected from pure-breeding populations, and a pair of reciprocal crosses is performed. The cross results are shown below.

Cross 1: P₁: Male leopard x male mottled
F₁: All mottled
F₂: 70 mottled, 22 leopard
Cross 2: P₁: Male mottled x female leopard
F₁: All mottled
F₂: 50 mottled, 18 leopard

Which of the phenotypes is dominant? Explain your answer.
Open Question
A male mouse from a true-breeding strain of hyperactive animals is crossed with a female mouse from a true-breeding strain of lethargic animals. (These are both hypothetical strains.) All the progeny are lethargic. In the F₂ generation, all offspring are lethargic. What is the best genetic explanation for these observations? Propose a cross to test your explanation.
Open Question
Black skin color is dominant to pink skin color in pigs. Two heterozygous black pigs are crossed.

If these pigs produce a total of three piglets, what is the probability that two will be pink and one will be black?