122 CHAPTER 3 Indkopendent Assortment of Genes Number of progeny Unpacking Probl

Question

122 CHAPTER 3 Indkopendent Assortment of Genes Number of progeny Unpacking Problem 31 Mating phenotypes PC PPo G,C G,Po Befere aempring a solurion so this problem, try ansu 33. w following questions 1 PCx G, C 323 102 309 106 2 BCx P Po 220 206 65 72 3 RC)( G, C 723 229 4 RCx 5PPoxG,C 71 90 85 1. What does the word normal mean in this problen 2. The words line and strain are used in this po 3. Draw a simple sketch of the two parental flies 4. How many different characters are there in What do they mean, and are they interchangeable G, Po 405 389 0 their eyes, wings, and sexual differences. a. Which alleles are dominant? b. What are the most probable gernotypes for the parenes 5. How many phenotypes are there ia this p in each cross? which phenotypes go with which characters? 30. A mutant allele in mice causes a bent tail Six pairs of 6 What is the full phenotype of the Fi females mice were crossed. Their phenotypes and those of their progeny are given in the following table. N is normal 2 What is the full phenotype of the Fi males called she phenotype B is bent phenotype. Deduce the mode of in heritance of bent tail. 8. List the F: phenotypic ratios for each character tha came up with in answer to question 4 9. What do the Fe phenotypic ratios tell you? 10. What major inheritance pattern distinguishes se Cross All B All N linked inheritance from autosomal inheritance? 11. Do the F2 data show such a distinguishing 12. Do the F, data show such a distinguishing criterion 13. What can you learn about dominance in the F1? The 14. What rules about wild-type symbolism can youe B N 1B.NB,IN All B All B All N All B Al B, IN All N All B B B in deciding which allelic symbols to invent for thew 15. What does "deduce the inheritance of these phe a. Is it recessive or dominant? b. Is it autosomal or sex-linked? types" mean? e. What are the genotypes of all parents and progeny? Now try to solve the problem. If you are unable to list of questions about the things that you do not undersson Inspect the learning goals at the beginning of the chaper and ak 31. The normal eye color of Drosophila is red, but strains in which all flies have brown eyes are available. Similarlys yoursedlf which are relevant to your questions. If this approck doesn't work, inspect the Key Concepts of this chapter and sk wings are normally long, but there are strains with short wings A female from a pure line with brown eyes and short wings is crossed with a male from a normal pure line. The Fi consists of normal females and short-winged males. An F is then produced by intercrossing the Fi yourself which might be relevan to your questions 32. In a natural population of annual plants, a single plai found that is sickly looking and has yellowish leaves The plant is dug up and brought back to the laboraony Photosynthesis rates are found to be very low Polen from a normal dark-green-leaved plant is used to fertilas emasculated flowers of the yellowish plant. A hur seeds result, of which only 60 germinate. All the resulng Both sexes of F, flies show phenotypes as follows: red eyes, long wings i red eyes, short wings brown eyes, long wings brown eyes, short wings plants are sickly yellow in appearance. a. Propose a genetic explanation for the inheritane Deduce the inheritance of these phenotypes use clearly defined genetic symbols of your own invention. State the genotypes of all three generations and the genotypic proportions of the Fi and F attern b. Suggest a simple test for your model. c. Account for the reduced photosynthesis, sicklines and yellowish appearance

Explanation / Answer

Answer (Question No. 30):

A) Dominant

B) X-linked

C) Genotype of all parents and progeny

1. b/b X B/Y

2.B/b X b/Y

3.B/B X b/Y

4.b/b X b/Y

5.B/B X B/Y

6.B/b X B/Y

Explanation:

The trait is X-linked dominant as all the daughters, but none of the sons, of affected father are affected given mother is normal.

The genotype can be derived as B=affected X, b= normal X, and Y.

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