Exam 14: Mendel and the Gene

A black guinea pig crossed with an albino guinea pig produced 12 black offspring. When the albino was crossed with a second black animal, 6 blacks and 6 albinos were obtained. What is the best explanation for this genetic situation?

Phenylketonuria is an inherited disease caused by a recessive autosomal allele. If a woman and her husband are both carriers, what is the probability that their first child will be a phenotypically normal girl?

The following questions) refer to the pedigree chart in the figure provided for a family, some of whose members exhibit the dominant trait, W. Affected individuals are indicated by a dark square or circle. -What is the genotype of individual II- 5?

Sex Phenotype Number male wild 123 male yellow 116 female wild 240 Figure 14.1 -In a Drosophila experiment, a cross was made between homozygous wild- type females and yellow- bodied males. All of the resulting F₁s were phenotypically wild type. However, adult flies of the F₂ generation resulting from matings of the F₁s) had the characteristics shown in the figure above: A. Is the mutant allele for yellow body recessive or dominant? B. Is the yellow locus autosomal not X- linked) or X- linked?

Gene S controls the sharpness of spines in a type of cactus. Cactuses with the dominant allele, S, have sharp spines, whereas homozygous recessive ss cactuses have dull spines. At the same time, a second gene, N, determines whether or not cactuses have spines. Homozygous recessive nn cactuses have no spines at all. If doubly heterozygous SsNn cactuses were allowed to self- pollinate, the F₂ would segregate in which of the following ratios?

A homozygous tomato plant with red fruit and yellow flowers was crossed with a homozygous tomato plant with golden fruit and white flowers. The F₁ all had red fruit and yellow flowers. The following phenotypes were obtained in the F₂: Red fruit and yellow flowers-41 Red fruit and white flowers-7 Golden fruit and yellow flowers-8 Golden fruit and white flowers-44 How many map units separate these genes?

A man has extra digits six fingers on each hand and six toes on each foot). His wife and their daughter have a normal number of digits. Having extra digits is a dominant trait. The couple's second child has extra digits. What is the probability that their next third) child will have extra digits?

A man and woman are both of normal pigmentation and have a child who is albino without melanin pigmentation). Albinism is an autosomal not sex- linked) recessive trait. What are the genotypes of the albino's parents?

Pseudohypertrophic muscular dystrophy is a human disorder that causes gradual deterioration of the muscles. Only boys are affected, and they are always born to phenotypically normal parents. Due to the severity of the disease, the boys die in their teens. Is this disorder likely to be caused by a dominant or recessive allele? Is its inheritance sex- linked or autosomal?

Glucose- 6- phosphate dehydrogenase deficiency G6PD) is inherited as a recessive allele of an X- linked gene in humans. A woman whose father suffered from G6PD marries a normal man. a) What proportion of their sons is expected to be G6PD? b) If the husband was not normal but was G6PD deficient, would you change your answer in part a)?

The B- globin gene has many alleles. What is the maximum number of different alleles of the B- globin gene that could be carried by 6 children with the same mom and dad given that the parents are heterozygous?

When Mendel crossed yellow- seeded and green- seeded pea plants, all the offspring were yellow seeded. When he took these F₁ yellow- seeded plants and crossed them to green- seeded plants, what genotypic ratio is expected?

Gray seed colour in peas is dominant to white. Assume that Mendel conducted a series of experiments where plants with gray seeds were crossed among themselves, and the following progeny were produced: 302 gray and 98 white. a) What is the most probable genotype of each parent? b) Based on your answer in a) above, what genotypic and phenotypic ratios are expected in these progeny? Assume the following symbols: G = gray and g = white.)

Whenever the dominant allele of either or both) gene A or gene B is present, red colour is produced. A cross of AaBb × AaBb can be expected to yield how many red offspring out of 16? Assume the genes are not linked.

In Drosophila melanogaster, vestigial short) wings vg) are caused by a recessive allele of a gene that independently assorts with a gene pair that influences body hair. Hairy h) results in a hairy body. A cross is made between a fly with normal wings and a hairy body and a fly with vestigial wings and a normal body. The phenotypically normal F₁ flies were crossed among each other, and 1024 F₂ flies were reared. What phenotypes would you expect in the F₂, and in what actual numbers not ratios) would you expect to find them?

There are 40 different alleles for a gene involved in immune function. What is the maximum number of alleles that a human can have?

A man and woman are both of normal pigmentation, but both have one parent who is albino without melanin pigmentation). Albinism is an autosomal not sex- linked) recessive trait. What is the probability that their first child will be an albino?

A man who carries an allele of an X- linked gene will pass it on to

Hemophilia is caused by several genetic factors; one, a recessive allele of an X- linked gene, is the subject of this problem. Assume that a man with hemophilia marries a normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia?

In rabbits, the homozygous CC is normal, Cc results in deformed legs, and cc results in very short legs. The genotype BB produces black fur, Bb brown fur, and bb white fur. If a cross is made between brown rabbits with deformed legs and white rabbits with deformed legs, what percentage of the offspring would be expected to have deformed legs and white fur?