Exam 11: Mendel and the Gene Idea

Tallness (T)in snapdragon plants is dominant to dwarfness (t),and red (C^R)flower color is not dominant to white (C^W).The heterozygous condition results in pink (C^RC^W)flower color.A dwarf red snapdragon is crossed with a plant homozygous for tallness and white flowers.What are the genotype and phenotype of the F₁ individuals?

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.True-breeding red-flowered long radishes are crossed with true-breeding white-flowered radishes.All of the F₁ offspring are purple-flowered and long radishes.In the F₂ generation of this cross,which of the following phenotypic ratios would be expected?

Which of the following statements correctly describes a dihybrid cross?

Black fur in mice (B)is dominant to brown fur (b).Short tails (T)are dominant to long tails (t).What fraction of the progeny of crosses BbTt × BBtt will be expected to have black fur and long tails?

Why did Mendel continue some of his experiments to the F₂ generation?

In a particular plant,leaf color is controlled by gene locus D.Plants with at least one D allele have dark green leaves,and plants with the homozygous recessive dd genotype have light green leaves.A true-breeding dark-leaved plant is crossed with a light-leaved one,and the F₁ offspring is allowed to self-pollinate.The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure above,where 1,2,3,and 4 represent the genotypes corresponding to each box within the square.Which of the plants will be true-breeding?

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative.Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r,respectively.Which of the following is a possible partial genotype for the mother?

Which of the following statements describes the major reason that an individual with the genotype AaBbCCDdEE can make many kinds of gametes?

The addition rule of probability can be defined as

In a particular plant,leaf color is controlled by gene locus D.Plants with at least one D allele have dark green leaves,and plants with the homozygous recessive dd genotype have light green leaves.A true-breeding dark-leaved plant is crossed with a light-leaved one,and the F₁ offspring is allowed to self-pollinate.The predicted outcome of the F₂ is diagrammed in the Punnett square shown in the figure above,where 1,2,3,and 4 represent the genotypes corresponding to each box within the square.Which of the boxes correspond(s)to plants with a heterozygous genotype?

Why did the F₁ offspring of Mendel's classic pea cross always look like one of the two parental varieties?

Two true-breeding stocks of pea plants are crossed.One parent has red axial flowers,and the other has white terminal flowers;all F₁ individuals have red axial flowers.The genes for flower color and location assort independently.If 1,000 F₂ offspring resulted from the cross,approximately how many of them would you expect to have red terminal flowers?

Drosophila (fruit flies)usually have long wings (+ is the symbol used to represent this allele),but mutations in two different genes can result in bent wings (bt)or vestigial wings (vg).In symbolizing fruit fly alleles,it is common to use two letters as opposed to only one.If a homozygous bent wing fly is mated with a homozygous vestigial wing fly,which of the following offspring would you expect?

Labrador retrievers have black,brown,or yellow fur.Fur color is controlled by two genes,one of which exhibits epistasis.Black (B)is dominant over brown (b)in one gene,and (E)is dominant over (e)in the other gene.The (E)gene is epistatic to the (B)gene.In a cross of a black female with a brown male,results can be all black puppies,1/2 black to 1/2 brown puppies,or 3/4 black to 1/4 yellow puppies.In one cross of black × black,the results were as follows:9/16 black,4/16 yellow,3/16 brown. The genotype eebb must result in which of the following?

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.The relationship between genes S and N is an example of

A scientist discovers a DNA-based test for one allele of a particular gene.This and only this allele,if homozygous,produces an effect that results in death at or about the time of birth.Which of the following statements describes the best use of this discovery?

-The figure above represents a pedigree for a family in which dark-shaded symbols represent individuals with one of the two major types of colon cancer.Numbers under the symbols are the individuals' age at the time of diagnosis.A slash through the symbol indicates that the individual is deceased.In each generation of this family after generation I,the age at diagnosis is significantly lower than would be found in nonfamilial (sporadic)cases of this cancer (~63 years).What is the most likely reason?

Labrador retrievers are black,brown,or yellow.In a cross of a black female with a brown male,results can be all black puppies,1/2 black to 1/2 brown puppies,or 3/4 black to 1/4 yellow puppies.How many genes must be responsible for these coat colors in Labrador retrievers?

How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDdEE?

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?