You Continue Your Analysis by Crossing the Forked and Twist Lines Your Results Are as Follows
Unformatted text preview: 2019/11/3 Week 8 Practice Problems: Genetics I Week 8 Practice Problems: Genetics I Due: 11:59pm on Friday, October 18, 2019 You will receive no credit for items you complete after the assignment is due. Grading Policy Determining Genotype: Pea Pod Color A botanist has acquired a group of sweet pea plants. All of the plants have yellow pea pods (the recessive trait), except for one, which has green pea pods (the dominant trait). Pea pod color is a trait caused by a single gene. In this tutorial, you will determine how the botanist can identify the genotype of the green pea pod, and how this relates to Mendel's laws and meiosis. Part A - Identifying the genotype How could the botanist best determine whether the genotype of the green-pod plant is homozygous or heterozygous? You did not open hints for this part. ANSWER: Cross the green-pod plant with a yellow-pod plant. Cross the green-pod plant with another green-pod plant. Self-pollinate the green-pod plant. Part B Complete previous part(s) This botanist used the same logic to reach her conclusions as Mendel used in his experiments. Part C Complete previous part(s) Part D Complete previous part(s) Mendel's Law of Segregation This tutorial introduces Mendel's law of segregation of alleles using monohybrid crosses, the addition and multiplication rules, conditional probability, and binomial probability. In this tutorial you will investigate how alleles segregate during meiosis. You will also explore how this segregation, in conjunction with random gamete fusion, allows geneticists to predict the outcome of genetic crosses using simple rules of probability. Part A - Allele segregation and gamete formation One character in peas that Mendel studied was yellow versus green seeds. A cross between a homozygous yellow line (YY) and a homozygous green line (yy) will result in F1 plants that are heterozygous (Yy) for this trait and produce yellow seeds. When an F1 plant undergoes meiosis, what gamete types will it produce, and in what proportions? You did not open hints for this part. ANSWER: 1/8 2019/11/3 Week 8 Practice Problems: Genetics I 1 2 1 4 3 4 1 2 1 2 Yy Yy Y y Y y Y y YY yy 1 2 3 4 1 4 1 2 1 2 Part B - Punnett square Punnett squares are convenient ways to represent the types and frequencies of gametes and progeny in experimental crosses. This Punnett square shows the results of a Yy x Yy cross to form F2 progeny. Use your understanding of Mendel's law of segregation and the rules of probability to complete the Punnett square for this cross. First identify the gametes. Use pink labels to identify the male and female gamete types and white labels to identify the gamete frequencies. Then identify the F2 progeny. Use pink labels to identify the progeny genotypes and white labels to identify the progeny frequencies. You did not open hints for this part. ANSWER: Reset Help Y y YY Yy yy 1 1 1 9 3 8 4 2 16 4 G2 G2 G1 G2 G2 G1 G2 G1 G1 G2 G1 G2 G1 G2 Part C - Using the Punnett square to make predictions Use the completed Punnett square in Part B to answer the questions below about the F2 generation. Drag the probabilities on the left to the blanks on the right to answer the questions. Terms can be used once, more than once, or not at all. You did not open hints for this part. ANSWER: 2/8 2019/11/3 Week 8 Practice Problems: Genetics I Reset 1 1 4 1 2 27 64 1 64 1 3 3 Help 1. What is the probability that an F2 seed chosen at random will be yellow? 2. What is the probablity that an F2 seed chosen at random from among the yellow seeds will breed true when selfed? 3. What is the probability that three F2 seeds chosen at random will include at least one yellow seed? 4. What is the probability that three F2 seeds chosen at random will include one green seed and two yellow seeds? 4 2 3 9 64 63 64 9 16 0 Mendel's Law of Independent Assortment In this tutorial you will examine dihybrid crosses: crosses where alleles at separate loci assort independently into gametes at meiosis. You will also use logic to determine unknown genotypes, phenotypes, and genetic ratios from given data. Part A - Deducing phenotypes and genotypes of selfed parents Mendel studied pea plants dihybrid for seed shape (round versus wrinkled) and seed color (yellow versus green). Recall that the round allele (R) is dominant to the wrinkled allele (r) and the yellow allele (Y) is dominant to the green allele (y). The table below shows the F1 progeny that result from selfing four different parent pea plants. Use the phenotypes of the F1 progeny to deduce the genotype and phenotype of each parent plant. Complete the table by dragging the correct label to the appropriate location. Labels can be used once, more than once, or not at all. You did not open hints for this part. ANSWER: 3/8 2019/11/3 Week 8 Practice Problems: Genetics I Reset Help RRYY RrYY RRYy RrYy RRyy Rryy rryy rrYy Part B - Deducing genotypes of crossed parents A plant grown from a [round, yellow] seed is crossed with a plant grown from a [wrinkled, yellow] seed. This cross produces four progeny types in the F1: [round, yellow], [wrinkled, yellow], [round, green], and [wrinkled, green]. Use this information to deduce the genotypes of the parent plants. Indicate the genotypes by dragging the correct label to the appropriate location. You did not open hints for this part. ANSWER: Reset Help RRYY RrYY RrYy rrYy rrYY RRyy Rryy rryy RRYy Part C Complete previous part(s) 4/8 2019/11/3 Incomplete Dominance and Codominance Week 8 Practice Problems: Genetics I You are studying leaf development in a member of the mustard family. You identify several mutants of interest in this plant and make pure (truebreeding) lines of each mutant for further study. Part A - Determining relationships between alleles You decide to conduct a genetic analysis of these mutant lines by crossing each with a pure wild-type line. The numbers in the F2 indicate the number of progeny in each phenotypic class. From these results, determine the relationship between the mutant allele and its corresponding wild-type allele in each line. Label each mutant line with the best statement from the list below. Labels may be used once, more than once, or not at all. You did not open hints for this part. ANSWER: Reset Help The mutant allele is recessive to its corresponding wildtype allele. The mutant allele is neither dominant nor completely recessive to its corresponding wild-type allele. The mutant allele is dominant to its corresponding wildtype allele. Part B - Crossing the forked and pale mutants You continue your genetic analysis by crossing the forked and pale mutant lines with each other. The leaves of the F1 are light green (intermediate between pale and wild-type leaves) and forked. The F2 has six phenotypic classes, as shown below. You designate the forked mutant allele as F (wild type = f+ ) and the pale mutant allele as p (wild type = P). 5/8 2019/11/3 Week 8 Practice Problems: Genetics I 1. Consider the alleles for leaf color first. Drag the white labels to the white targets to identify the genotype of each F2 class. Remember that p (the pale mutant allele) and P (the wild-type allele) are incompletely dominant to each other. 2. Consider the alleles for leaf shape next. Drag the blue labels to the blue targets to identify the genotype of each F2 class. Remember that F (the forked mutant allele) is dominant to f + (the wild-type allele). Labels may be used once, more than once, or not at all. For help getting started, see the hints. You did not open hints for this part. ANSWER: Reset Help PP Pp pp P_ G1 G2 G1 G2 G1 G2 G1 G2 G1 G2 G1 G2 FF Ff + f+f + F_ Part C - Crossing the forked and twist mutants You continue your analysis by crossing the forked and twist lines. Your results are as follows: Which of the following statements best explains the outcome of this cross? You did not open hints for this part. ANSWER: The forked mutation and the twist mutation are codominant alleles of the same locus. The twist mutation is incompletely dominant to the forked mutation. The forked mutation is incompletely dominant to the twist mutation. The forked mutation has recombined with the twist mutation. Part D Complete previous part(s) Sex Linkage A trait controlled by a gene located on either sex chromosome is called a sex-linked trait. In human genetics, however, this term has historically referred specifically to a trait controlled by a gene on the X chromosome (also called an X-linked trait). In this tutorial, you will explore the pattern of inheritance of sex-linked traits in humans and other animals. 6/8 2019/11/3 Week 8 Practice Problems: Genetics I Part A - The inheritance of a skin condition in humans Consider the following family history: Bob has a genetic condition that affects his skin. Bob's wife, Eleanor, has normal skin. No one in Eleanor's family has ever had the skin condition. Bob and Eleanor have a large family. Of their eleven children, all six of their sons have normal skin, but all five of their daughters have the same skin condition as Bob. Based on Bob and Eleanor's family history, what inheritance pattern does the skin condition most likely follow? You did not open hints for this part. ANSWER: Y-linked X-linked dominant autosomal dominant autosomal recessive X-linked recessive Part B - A sex-linked gene for eye color in Drosophila The inheritance of eye color in Drosophila is controlled by genes on each of the fly's four chromosome pairs. One eye-color gene is on the fly's X chromosome, so the trait is inherited in a sex-linked manner. For this sex-linked trait, the wild-type (brick red) allele is dominant over the mutant vermilion (bright red) allele. A homozygous wild-type female fly is mated with a vermilion male fly. X + X + v × X Y Predict the eye colors of F1 and F2 generations. (Assume that the F1 flies are allowed to interbreed to produce the F2 generation.) Drag the correct label to the appropriate location in the table. Labels can be used once, more than once, or not at all. You did not open hints for this part. ANSWER: Reset Help all wild type all vermilion 1/2 wild type 1/2 vermilion 3/4 wild type 1/4 vermilion Part C - The inheritance of both a sex-linked trait and an autosomal trait in humans Red-green color blindness is due to an X-linked recessive allele in humans. A widow's peak (a hairline that comes to a peak in the middle of the forehead) is due to an autosomal dominant allele. Consider the following family history: 7/8 2019/11/3 Week 8 Practice Problems: Genetics I A man with a widow's peak and normal color vision marries a color-blind woman with a straight hairline. The man's father had a straight hairline, as did both of the woman's parents. Use the family history to make predictions about the couple's children. Drag the correct label to the appropriate location in the table. Not all labels will be used. You did not open hints for this part. ANSWER: Reset Help 1/2 3/4 1/4 0 1 Score Summary: Your score on this assignment is 0.0%. You received 0 out of a possible total of 10 points. 8/8 ...
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