BROOKER BIOLOGY
5th Edition
ISBN: 9781307656152
Author: BROOKER
Publisher: MCG/CREATE
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Chapter 18, Problem 2COQ
Mendel studied seven traits in garden pea plants, and this species happens to have seven different chromosomes. It has been pointed out that Mendel was very lucky not to have conducted crosses involving two traits governed by genes that are closely linked on the same chromosome, because the results would have confounded his theory of independent assortment. It has even been suggested that Mendel may not have published data involving traits that were linked! An article by Stig Blixt 1975. (Why Didn’t Gregor Mendel Find Linkage? Nature 256: 206, 1975) considers this issue. Look up this article, and discuss why Mendel did not find linkage.
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As you know Mendel’s main contribution to genetics was his proposing a model of particulate inheritance. This discovery contradicted the widely held belief that blending inheritance was the true theory that explained hereditary traits. One advantage that Mendel had in choosing garden peas (Pisum sativum) was that he could either allow the pea flowers on a plant to self-pollinate or he could deliberately cross-pollinate the flowers. For his single locus crosses of pure-breeding lines, he would take the F2 offspring of the dominant phenotype (such as yellow seeds) and ensure that each yellow-seeded plant would self-pollinate. He was able to show that 1/3 of all the yellow-seeded plants in this generation bred true while the other 2/3 of the yellow seeded plants showed segregation. Do you believe that this extra experiment gave additional important evidence for the particulate theory of inheritance or did the offspring from the F1 x F1 cross provide enough evidence of Mendel’s First Law?…
A pure strain of Mendel's peas, dominant for all seven of his independently assorting genes, was testcrossed.
How many different kind of gametes could each of the parents produced?
We have crossed true-breeding flies today. Wild type to mutant. Their phenotypes were wt and vg se. (Let’s not worry about males and females for now, just assume both genes are autosomal, which is normal in a Mendelian experiment).
The results of a cross are phenotypes. I will be asking you for numbers or a ratio of phenotype numbers you expect to see in the offspring from this cross. To answer this, you’ll need to start with the genotypes of parents, then write their gametes, then write the offspring genotypes, then get the phenotypes based on them.
Predict the results of this cross:
In case both mutations are recessive;
In case both mutations are dominant;
In case vestigial wings are recessive and the sepia eyes are dominant.
Chapter 18 Solutions
BROOKER BIOLOGY
Ch. 18.2 - Prob. 1CCCh. 18.3 - Prob. 1CCCh. 18.3 - Prob. 1CSCh. 18.5 - Prob. 1CSCh. 18.5 - Prob. 1CCCh. 18.6 - Prob. 1EQCh. 18.6 - Prob. 2EQCh. 18.6 - Prob. 3EQCh. 18.6 - Prob. 1CCCh. 18.6 - Prob. 2CC
Ch. 18 - Which of the following is an example of an...Ch. 18 - Prob. 2TYCh. 18 - A female mouse that is Igf2 Igf2 is crossed to a...Ch. 18 - Prob. 4TYCh. 18 - Prob. 5TYCh. 18 - Prob. 6TYCh. 18 - Prob. 7TYCh. 18 - Prob. 8TYCh. 18 - Based on the ideas proposed by Morgan, which of...Ch. 18 - Extranuclear inheritance occurs because a. certain...Ch. 18 - Define epigenetics. Are all epigenetic changes...Ch. 18 - What is a Barr body? How is its structure...Ch. 18 - Core Concept: Information A core concept of...Ch. 18 - Prob. 1COQCh. 18 - Mendel studied seven traits in garden pea plants,...
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- When Mendel did his experiments, it was the case that the genes for each trait were on separate pairs of homologous chromosomes. For example, the genes for pod color were on one pair of chromosomes and the genes for the seed coat were on a different pair of chromosomes. What if the genes for the two traits were on the same chromosome? (That is, if the gene for pod color was on the same chromosome as the gene for seed coat.) Would Mendel’s 2nd Law still hold? Why or why not?arrow_forwardGenes A and B are on two different chromosomes. You construct a Punnett Square to to show the expected genotypes in the offspring of a cross between these two genotypes: AaBB x AaBb. What are the dimensions of the smallest Punnett square you can make to show the expected results? (e.g., 2x2, 4x1. Don’t worry about the order of the two numbers if they differ. That is, 4x8 is the same as 8x4)arrow_forwardIn this program, you are provided with phenotype pair counts of F2 offspring at two research institutes. The key different between this work and previous work is that now we consider two genes instead of one. The phenotype pairs are the (shape, color) of peas from a pea plant. It turns out that there are two separate genes that code for these phenotypes. We shall call them Shape and Color. Gregor Mendel originally recorded these experiments in green peas. Using the notation: R = Round (dominant) allele at Shape gene; r = Wrinkled (recessive) allele at Shape gene; Y = Yellow (dominant) allele at Color gene; y = Green (recessive) allele at Color gene; then the shape and color of any pea can be determined by studying the genotypes at each gene. It turns out that, when one mates a plant that is homozygous for the dominant alleles (RRYY) with a plant that is homozygous for the recessive alleles (rryy), the F1 generation are heterozygous at both genes, as with a single gene disorder.…arrow_forward
- Mendel obtained his initial pea plant varieties from local breeders who were developing new varieties that might be useful or interesting. To generate these new varieties, breeders formed hybrids between existing varieties of different phenotypic characteristics by cross-pollination, using techniques they doubtless taught to Mendel. After producing a hybrid, they allowed several generations of self-pollination, as happens naturally if the flowers are not disturbed. i. How many generations would it take for a breeder to have produced new pure-breeding varieties using this approach? ii. What is the probability that an individual in each of these generations (F2, F3, and F10) would be homozygous for one or the other allele of this gene? [Broad hint: if they’re not heterozygous, they’re homozygous!] please answer and explain properlyarrow_forwardMendel crossed pea plants that produced round seeds with those that produced wrinkled seeds and self-fertilized the progeny. In the F2, he observed 5474 round seeds and 1850 wrinkled seeds. Using the letters W and w for the seed texture alleles, diagram Mendel's crosses, showing the genotypes of the plants in each generation. Are the results consistent with the Principle of Segregation?arrow_forwardIn letter B: If the map distance equals the number of recombinant/total of offspring, wouldn't it be 24/806 x 100? Wouldn't we add both recombinants? Can you explain letter C? I don't grasp that concept well. And since I'm using my question already, would you be able to answer D. Thank you!arrow_forward
- In Mendel's experiments, he obtained the following results: Which phenotypes can be said to be dominant?arrow_forwardA geneticist discovers an obese mouse in his laboratory colony. He breeds this obese mouse with a normal mouse. All the F1 mice from this cross are all normal in size. When he interbreeds two F1 mice, eight of the F2 mice are normal in size and two are obese. The geneticist then intercrosses two of his obese mice, and he finds that all of the progeny from this cross are obese. These results lead the geneticist to conclude that obesity in mice results from a recessive allele. A second geneticist at a different university also discovers an obese mouse in her laboratory colony. She carries out the same crosses as the first geneticist did and obtains the same results. She also concludes that obesity in mice results from a recessive allele. One day the two geneticists meet at a genetics conference, learn of each other’s experiments, and decide to exchange mice. They both find that when they cross two obese mice from the different laboratories, all the offspring are normal, but when they…arrow_forwardA dihybrid cross is performed between two heterozygous individuals (heterozygous for two traits). The resulting offspring had 62 individuals that were dominant for trait 1 and 2 (D/D), 7 individuals that were R/R, 21 individuals that were R/D, and 25 individuals that were D/R. Using Mendelian inheritance as the null hypothesis, use χ2 analysis to determine if the trait follows Mendelian inheritance. A. How many D/D phenotype offspring are expected? B. How many R/D phenotype offspring are expected? C. How many degrees of freedom are there? D. What is your calculated χ2 value? E. What is the critical value if using a probability of 0.05? F. Does the trait follow Mendelian inheritance?arrow_forward
- A pure strain of Mendel’s peas, dominant for all seven of his independently assorting genes, was testcrossed. (a) How many different kinds of gametes could each of the parents produce? (b) How many different gametes could the F1 produce? (c) If the F1, was testcrossed, how many phenotypes would be expected in the offspring and in what proportions? d) How many genotypes would be expected in the F2? (e) How many combinations of F1 gametes are theoretically possible (considering, e.g., AABBCCDDEEFFGG sperm nucleus x aabbccddeefigg egg nucleus a different combination than AABBCCDDEEFFGG egg nucleus x aabbccddeeflgg sperm nucleus)? (f) How many different kinds of matings could theoretically be made among the F2?arrow_forwardMendel counted thousands of pea plants for each cross in his experiments before reaching his conclusions. Why did he need to count so many? Each kernel you counted in this lab is an offspring resulting from sexual reproduction. Name three processes that contribute to variation in sexual reproduction.arrow_forwardA student whose hobby is fishing pulled a carp out of Cayuga Lake that was very unusual: it had no scales on its body. She decided to investigate whether this strange “nude” phenotype had a genetic basis. She obtained some inbred carp that were pure-breeding for the wild-type scale pattern in which the fish had scales covering their body. She crosses these wild-type fish with her nude fish. To her surprise, the F1 progeny were wild-type fish and fish with a single, linear row of scales on the sides of their body (i.e. “linear). The ratio of these progeny was 2:1. She then crosses some of her F1 fish and obtains four phenotypes: wildtype, linear, nude and a new phenotype in which the fish had a few scales scattered over their body (i.e. “scattered”). The ratio of these offspring was 6:3:2:1. In the space below - answer the following questions: (use the letters S/s for scale production and L/l for scale pattern) How many genes are involved in producing scales on these fish? - answer:…arrow_forward
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