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
- 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 is the expected outcome of phenotypes?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 information do you know based on the question and your understanding of the topic?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_forward
- In 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_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
- In guinea pigs, rough coat (R) is dominant to smooth coat (r). If a homozygous rough-coated animal is crossed with a smooth-coated one: What will be the phenotype(s) of the F1 generation? What will be the phenotype(s) of the F2 generation? What will be the phenotype(s) of the offspring resulting from a cross of an F1 individual back to its rough parent? What will be the phenotype(s) of the offspring of a cross of an F1 individual back to its smooth parent?arrow_forwardSuppose that you are tending a mouse colony at a genetic research institute, and one day you discover a mouse with twisted ears. You breed this mouse with twisted ears and find that the trait is inherited. Both male and female mice may have twisted ears, but when you cross a twisted-eared male with a normal-eared female, you obtain results that differ from those obtained when you cross a twisted-eared female with a normal-eared male: the reciprocal crosses give different results. Describe how you would determine whether this trait results from a sexlinked gene, a sex-influenced gene, genetic maternal effect, a cytoplasmically inherited gene, or genomic imprinting. What crosses would you conduct, and what results would be expected with these different types of inheritance?arrow_forward) Cats also have a locus (gene) for a character called agouti. In cats with agouti fur, pigment is unevenly distributed (see Fig. 1). The agouti allele is dominant to the allele for regular fur. A male cat who long haired and is heterozygous for agouti fur is crossed with a female who has regular, non-agouti fur and is homozygous for short fur. a) What are the genotypes of these cats? b) What are all of the possible allelic combinations in the gametes from each of these cats? c)What are all of the possible phenotypic combinations of these characters in their kittens and in what ratios?arrow_forward
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