Concept explainers
In mice, a trait called snubnose is recessive to a wild-type nose, a trait called pintail is dominant to a normal tail, and a trait called jerker (a defect in motor skills) is recessive to a normal gait. Jerker mice with a snubnose and a pintail were crossed to normal mice, and then the
560 jerker, snubnose, pintail
548 normal gait, normal nose, normal tail
102 jerker, snubnose, normal tail
104 normal gait, normal nose, pintail
77 jerker, normal nose, normal tail
71 normal gait, snubnose, pintail
11 jerker, normal nose, pintail
9 normal gait, snubnose, normal tail
Construct a genetic map that shows the order of these genes and distances between them.
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Chapter 6 Solutions
Genetics: Analysis and Principles
- Coat color in mice is influenced by two genes, one for color (A) and one for the amount of pigment production (C). Mice with the wild type agouti coat color have a yellowish to brownish color. Mice also have a gene that determines the amount of pigment the hair produces. Multiple crosses were made between male and female mice that were each heterozygous for both traits (AaCc). The data table shows the number of mice of each coat type. Calculate the average F1 generation coat color to answer the question. Which of the following is the most probable interaction between the two genetic loci, A and C, based on the average F1 ratio results? A - The two loci show an epistatic pattern with the loci C epistatic to loci A. B - The two loci show a codominant pattern with both loci affecting coat color. C - The two loci interact in a Mendelian pattern with A being completely dominant over C. D - The two loci show an incomplete dominance pattern with neither loci A nor C being dominant.arrow_forwardIn mice, black coat color (B) is dominant over brown (b), and a solid pattern (S) is dominant to white spotted (s). Color and spotting are controlled by genes that assort independently. A homozygous black spotted mouse is crossed with a homozygous brown solid mouse. All of the F1 mice are black and solid. In biology class one day you see a black solid mouse run across your desk. You and your classmates manage to trap the mouse and decide to attempt to discover it’s genotype. In order to do this you perform a testcross with a laboratory mouse. You perform the testcross and find that ½ of the offspring from the testcross are black and solid and ½ are black and spotted. What is the genotype of the classroom mouse?arrow_forwardTwo recessive traits in mice—droopy ears and flaky tail—arecaused by genes that are located 6 mu apart on the same chromosome.A true-breeding mouse with normal ears (De) and a flaky tail ( ft)was crossed to a true-breeding mouse with droopy ears (de) and anormal tail (Ft). The F1 offspring were then crossed to mice withdroopy ears and flaky tails. If this testcross produced 100 offspring,what is the expected outcome of phenotypes?arrow_forward
- Two recessive traits in mice—droopy ears and flaky tail—arecaused by genes that are located 6 mu apart on the same chromosome.A true-breeding mouse with normal ears (De) and a flaky tail ( ft)was crossed to a true-breeding mouse with droopy ears (de) and anormal tail (Ft). The F1 offspring were then crossed to mice withdroopy ears and flaky tails. If this testcross produced 100 offspring,What topic in genetics does this question address?arrow_forwardPink eye and albinism are two recessive traits found in the deer mouse, Peromyscus maniculatus. In mice with pink eye, the eye is devoid of color and appears pink from the blood vessels within it. Albino mice are completely lacking color both in their fur and in their eyes. F. H. Clark crossed pink‑eyed mice with albino mice; the resulting F1 had normal coloration in their fur and eyes. He then crossed these F1 mice with mice that were pink‑eyed and albino and obtained the mice shown in the table below. It is very hard to distinguish between mice that are albino and mice that are both pink‑eyed and albino, so he combined these two phenotypic classes (F. H. Clark, 1936, Journal of Heredity 27:259−260). Match the expected numbers of progeny with each phenotype if the genes for pink‑eye and albinism assort independently. Phenotype Observed Expected wild type, wild type 12 wild type, pink eyes 62 albino, wild type, or pink eyes 78 Total 152 152 Answer…arrow_forwardIn silkmoths (Bombyx mori), red eyes (re) and white-banded wings (wb) are encoded by two mutant alleles that are recessive to those that produce wild-type traits (re+ and wb+); these two genes are on the same chromosome. A moth homozygous for red eyes and white-banded wings is crossed with a moth homozygous for the wild-type traits. The F1 have wild-type eyes and wild-type wings. The F1 are crossed with moths that have red eyes and white-banded wings in a testcross. The progeny of this testcross are wild-type eyes, wild-type wings red eyes, wild-type wings wild-type eyes, white-banded wings red eyes, white-banded wings a. What phenotypic proportions would be expected if the genes for red eyes and for white-banded wings were located on different chromosomes? b. What is the rate of recombination between the gene for red eyes and the gene for white-banded wings?arrow_forward
- In guinea pigs, a black coat (B) is dominant over a white coat (b), and straight hair (S) is dominant over curly hair (s). The genes for coat color and type of hair are located on different chromosomes. A heterozygous, black, and straight hair guinea pig (BbSs) was test crossed. A guinea pig heterozygous for both traits mated with a homozygous recessive guinea pig. What is the probability of having offspring with at least one dominant trait? Select one: a. 0.50 b. 0.00 c. 0.25 d. 0.75 e. 1.0arrow_forwardMouse fur color is affected by TWO unlinked loci. GG or Gg mice are agouti. Mice with genotype gg are albino since all pigment production is blocked, regardless of the phenotype at the second locus. At the other locus, the F allele (agouti coat) is dominant to the f allele (black coat). How many black mice would result from a cross between two agouti mice of genotype GgFf? (just write in the numeral)arrow_forwardWild-type mice have brown fur and short tails. Loss of function of a particular gene produces white fur, while loss of function of another gene produces long tails, and loss of function at a third locus produces agitated behavior. Each of these loss of function alleles is recessive. If a wild-type mouse is crossed with a triple mutant, and their F1 progeny is test-crossed, the following recombination frequencies are observed among their progeny. Produce a genetic map for these loci. Brown, short tailed, normal: 955 White, short tailed, normal: 16 Brown, short tailed, agitated: 0 White, short tailed, agitated: 36 Brown, long tailed, normal: White, long tailed, normal: Brown, long tailed, agitated: 46 0 14 White, long tailed, agitated: 933arrow_forward
- Within a mouse population, the black fur allele (B) is dominant to the white fur allele (b) and the short whisker allele (S) is dominant to the long-whisker allele (s). A heterozygous black-furred short-whiskered mouse is crossed with a homozygous white-furred long-whiskered mouse. What percentage of the offspring will be black-furred with long whiskers?arrow_forwardIn mice, black color (B) is dominant to white (b). On different homologous chromosomes, a dominant allele (A) produces a band of yellow just below the tip of each hair in mice with black fur. This gives a frosted appearance known as agouti. Expression of the recessive allele (a) results in a solid coat color. If mice that are heterozygous at both locations are crossed, what is the expected phenotypic ratio of their offspring? Use the rules of probability instead of a huge Punnett square.arrow_forwardIn roses, red petals (r) and waxy texture (wx) are encoded by two mutant alleles that are recessive to those that produce wild-type traits; yellow petals (r+) and soft texture (wx+). A rose homozygous for red petals and waxy texture is crossed to a rose homozygous for the wild-type traits. The F1 have yellow petals and soft texture. The F1 are crossed with roses that have red petals and waxy texture in a testcross. The progeny of this testcross are (1000 total): Yellow petals, soft texture 300 Yellow petals, waxy texture 126 Red petals, soft texture 110 Red petals, waxy texture 464 What is the genetic distance between red petals and waxy texture? a.57.4 b.76.4 c.23.6 d.30.9 e.42.6arrow_forward
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