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INTERPRET DATA Using the graph in Figure 11-20, determine how many offspring were involved in the hypothetical cross studying skin color. What percentage had the lightest skin possible? the darkest skin possible?
Figure 11-20 Polygenic inheritance in human s pigmentation
This simplified example assumes that skin pigmentation in humans is governed by alleles of three unlinked loci. The alleles producing dark skin (A, B, and C) are represented by capital letters, but they are not dominant. Instead, their effects are additive. The number of dark dots, each signifying an allele producing dark skin, is counted to determine the phenotype. A wide range of
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Chapter 11 Solutions
Biology (MindTap Course List)
- Hemophilia and color blindness are both recessive conditions caused by genes on the X chromosome. To calculate the recombination frequency between the two genes, you draw a large number of pedigrees that include grandfathers with both hemophilia and color blindness, their daughters (who presumably have one chromosome with two normal alleles and one chromosome with two mutant alleles), and the daughters sons. Analyzing all the pedigrees together shows that 25 grandsons have both color blindness and hemophilia, 24 have neither of the traits, 1 has color blindness only, and 1 has hemophilia only. How many centimorgans (map units) separate the hemophilia locus from the locus for color blindness?arrow_forwardFigure 8.10 In pea plants, purple flowers (P) are dominant to white (p), and yellow peas (Y) are dominant to green (y). What are the possible genotypes and phenotypes for a cross between PpYY and ppYy pea plants? How many squares would you need to complete a Punnett square analysis of this cross?arrow_forwardA cross like this (between two individuals heterozygous for two traits) is often referred to as a "two-point test cross". The expected ratio of phenotypes if the two traits are caused by unlinked genes displaying simple Mendelian dominant inheritance is 9:3:3:1. For this ratio, match each term of the ratio with the appropriate phenotype Wrinkled and green peas 1. 9 Round and yellow peas 2. 3 Round and green peas 3. 1 Wrinkled and yellow peas > >arrow_forward
- Fruit flies having one allele for curly wings (Cy) and one allele for normal wings (Cy+) develp curly wings. Fruit flies homozygous for normal wings (Cy+) develop normal wings. When two curly-winged flies were crossed, 204 curly-winged and 98 normal-winged flies. In fact, all crosses between curly-winged flies produce nearly the same curly-winged to normal-winged ratio. How would you explain these results? The Cy allele is epistatic to the Cy+ allele. The Cy+ allelle shows partial dominance over the Cy allele. The Cy allele is dominant for the curly phenotype and is lethal when homozygous. The Cy+ allele is dominant over the Cy allele and is lethal when homozygous. The Cy+ and Cy alles are co-dominant.arrow_forwardSeed color is controlled by 3 independently assorting bi-allelic genes (P, Q, R), such that homozygote pp exhibits recessive epistasis over the seed color pathway, converting a white pigment into yellow, which then becomes orange in the presence of a Q allele, or red in the presence of R. Individuals with both Q and R alleles show pink seeds. In a cross of PpQqRr individuals with ppqqrr individuals, what is the ratio of white-seeds to red seeds? а. 1:4 b. 2:3 с. 1:1 d. 4:1 e. 1:5arrow_forwardMendelian ratios are modified in crosses involving autotetraploids.Assume that one plant expresses the dominant trait greenseeds and is homozygous (WWWW). This plant is crossed to onewith white seeds that is also homozygous (wwww). If only onedominant allele is sufficient to produce green seeds, predict theF1 and F2 results of such a cross. Assume that synapsis betweenchromosome pairs is random during meiosis.arrow_forward
- Q6. Guinea pigs, which were homozygous for long, black hair were crossed with ones which were homozygous for short, white hair. All the F1 offspring had short, black hair. (a) Using suitable symbols, draw a genetic diagram showing parents genotypes, to explain this result in F1 offspring. (b) Complete the Punnett square to show the results of interbreeding the F1 offspring. Gametesarrow_forwardThe allele G for yellow stigma is completely dominant to green (g). Supposing two strains of autotetraploid plants are available and their genotypes are as follows: GGgg – in this plant the gene is close to the centromere Gggg – in this plant the gene is far from the centromere If these two plants are crossed: a) provide the gametes that can be obtained from the two plants; b) provide the genotypic and phenotypic ratios of the offspring.arrow_forwardWith three-point genetic mapping, we can look at the inheritance of three linked genes and determine their order and map distance relative to each other on the chromosome. Suppose Gene G, Gene J, and Gene M are linked. An organism with the genotype GgJjMm was mated to an organism with the genotype ggjmm. The following phenotypes were seen in the offspring: Dominant for all three 13 Dominant for G and J Dominant for G and M 84 Dominant for J and M 389 Dominant for G only 401 Dominant for J only 96 Dominant for M only Recessive for all three 12 a. What the alleles in the parental gametes? b. What are the alleles in the double crossover gametes? c. What gene is in the middle of the three? d. What is the map distance between Gene G and Gene J? (Show all your work.) е. What is the map distance between Gene J and Gene M? (Show all your work.)arrow_forward
- Here is a cat family. Back fur is created by BB or Bb. White by bb. Based on what the pedigree shows, is this trait recessive or dominant? How do you know? 6. a) b) (4 --1 per individual ) Label everyone's genotype. In some cases you may have to say there is an X probability of, for example, BB and a Y probability of Bb. Hint: these probabilities might not be in halves or fourths. c) baby? No qualifiers! (Don't say, if this certain individual was genotype X, then there is a A% probability, but if this individual was genotype Y, then there is a B% probability. (SHOW WORK) If siblings Il-1 and Il-2 mate, what is the total, overall probability that they will have a white kitten II 1 2arrow_forwardIntroduction: A dihybrid cross is a cross between individuals that involves two pairs of contrasting traits. To Predict the results of a dihybrid, cross all possible combinations of the four alleles from each parent must be considered. You will examine a dihybrid cross involving both color and texture. Purple (P), is dominate to yellow (p), and smooth texture (S) is dominant to wrinkled (s). Both parent plants are heterozygous for both traits. Review genetics and the use of Punnett squares in a biology text before doing this experiment.MATERIALS: Assume you have ear of Corn. You need a heterozygous X heterozygous 9:3:3:1, purple/yellow, starchy/sweet. PROCEDURE: From above please write out: The crop The parental (P) cross phenotype, genotype, gametes Cross between two F1 Selfed testcross 1. First let us use a Punnett square to examine the theoretical outcome of the Heterozygous X Heterozygous dihybrid cross. USE a Punnett square. REMEMBER: a phenotype is how the offspring will…arrow_forwardTwo unlinked loci effect mouse hair color. AA or Aa mice are agouti. Mice with genotype aa are albino because all pigment production and deposition of pigment in hair is blocked. At the second locus, the B allele (black agouti coat) is dominant to the b allele (brown agouti coat). A mouse with an unknown genotype is mated with an albino mouse of genotype bbaa. Half of the offspring are albino, one quarter are black agouti, and one quarter are brown agouti. What is the genotype of the unknown parent?arrow_forward
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