Exam 14: Mendel and the Gene

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. A cross between a true- breeding sharp- spined cactus and a spineless cactus would produce

Regarding an allelic pair for flower colour in snapdragons, heterozygotes have pink flowers, whereas the two homozygotes have red flowers or white flowers. When plants with red flowers are crossed with plants with white flowers, what proportion of the offspring is expected to have pink flowers?

Snapdragons are flowers that come in a variety of colours, including red, pink, and white. A series of crosses wit snapdragons having flowers of different colours produced the following results: Pink × pink: 27 pink, 13 red, 14 white red × red: all red White × white: all white Pink × white: 29 pink, 26 white pink × red: 28 pink, 27 red white × red: all pink Based on the results, what is the most reasonable explanation for the inheritance of these flower colours?

What is the probability that a gamete from an individual with the genotype E₁E₂X₁X₁A₁A₂M₂M₂ will contain all paternally derived homologues?

A heterozygous, but phenotypically wild- type fruit fly gray body colour and normal wings) was mated to a black fly with vestigial wings. The offspring had the following phenotypic distribution: wild type, 720; Black- vestigial, 780; black- normal, 280; gray- vestigial, 220. What conclusion is likely from these results?

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 their first son will have hemophilia?

A couple has a child with Harman's ataxia a recessive disorder). If this couple has second child, what is the probability that child will have ataxia?

Figure 14.3 -The distance between two genes is a determinant of their recombination frequency. Based on the image below, which of the following sets of genes will show the greatest recombination frequency?

Radish flowers may be red, purple, or white. A cross between a red- flowered plant and a white- flowered plant yields all- purple offspring. The part of the radish we eat may be oval or long, with long being the dominant trait. If true- breeding red long radishes are crossed with true- breeding white oval radishes, the F₁ will be expected to be which of the following?

In humans, blue eyes are inherited as a recessive autosomal trait and colour blindness is an X- linked recessive trait. A woman with blue eyes and normal colour vision whose father was colour blind marries a man who also has normal colour vision. He has brown eyes, but his mother had blue eyes. Which of the following do you expect to be true for their sons?

The figure provided shows the pedigree for a family. Dark- shaded symbols represent individuals with one of the two major types of colon cancer. Numbers under the symbols are the individual's age at the time of diagnosis. Males are represented by squares, females by circles. From this pedigree, this trait seems to be inherited

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 female child will have albinism?

Suppose two AaBbCc individuals are mated. Assuming that the genes are not linked, what fraction of the offspring are expected to be homozygous recessive for the three traits?

Figure 14.2 -In the figure above, flower A was crossed with flower B to produce flower C. The phenotype of flower C is the result of

Assuming independent assortment for all gene pairs, what is the probability that the following parents, AABbCc × AaBbCc, will produce an AaBbCc offspring?

A sexually reproducing animal has two unlinked genes, one for head shape H) and one for tail length T). Its genotype is HhTt. Which of the following genotypes is possible in a gamete from this organism?

Different ratios occur in crosses with single gene pairs or two gene pairs. What types of ratios are likely to occur in crosses dealing with a single gene pair?

In tigers, a recessive allele causes a white tiger absence of fur pigmentation). If two phenotypically normal tigers that are heterozygous at this locus are mated, what percentage of their offspring is expected to be white?

In humans, ABO blood types refer to glyocproteins in the membranes of red blood cells. There are three alleles for this autosomal gene: IA, IB, and i. The IA allele codes for the A glycoprotein, the IB allele codes for the B glycoprotein, and the i allele doesn't code for any membrane glycoprotein. IA and IB are codominant, and i is recessive to both IA and IB. People with A type blood have the genotypes IAIA or IAi, people with type B blood are IBIB or IBi, people with type AB blood are IAIB, and people with O type blood are ii. If a woman with type AB blood marries a man with type O blood, which of the following blood types could their children possibly have?

Two individuals of genotype AABBCCDD and aabbccdd are mated. The F1 generation is interbred self- fertilized) to yield 5000 progeny. What proportion of the F2 is expected to be AabbCcDD?