The role of the gray crescent in amphibian development. Introduction: The amphibian egg is divided into two halves: animal half and vegetal half. The yolk remains concentrated in the vegetal half. The animal half is darkly stained due to the presence of a layer of pigment granules just below the surface. The sperm strikes the egg in the animal half and then the pigmented layer of cytoplasm rotates toward the site of the sperm entry, forming a crescent-shaped region. This region is just opposite to the site of sperm entry and known as gray crescent.

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Your goal is to produce black seeds resistant to mold. So you make the same cross again (between a homozygous black seeded, mold susceptible parent and a homozygous white seeded and mold resistant parent), and, again, advance progeny by SSD to create 100 F10 generation plants. Based on the information you obtained from your first crossing experiment (Question #4), how many F10 plants would you expect to have black seeds and be resistant to mold? Assume that a toxin produced by the mold fungus has been isolated. Only mold resistant seeds will germinate in the presence of the toxin. Could you use this toxin screening procedure to have segregation distortion work in your favor in the F2 generation? Explain your answer. Info from Question 4 a. P Locus (Seed Color): Hypothesis: The null hypothesis (H₀) is that seed color is controlled by alleles at a single locus. Observed Data: Total white seeds: 45 (resistant plants) + 6 (susceptible plants) = 51 Total black seeds: 7 (resistant…

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Chapter 50.2, Problem 1SB

Summary Introduction

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The role of the gray crescent in amphibian development.

Introduction:

The amphibian egg is divided into two halves: animal half and vegetal half. The yolk remains concentrated in the vegetal half. The animal half is darkly stained due to the presence of a layer of pigment granules just below the surface. The sperm strikes the egg in the animal half and then the pigmented layer of cytoplasm rotates toward the site of the sperm entry, forming a crescent-shaped region. This region is just opposite to the site of sperm entry and known as gray crescent.

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Your goal is to produce black seeds resistant to mold. So you make the same cross again (between a homozygous black seeded, mold susceptible parent and a homozygous white seeded and mold resistant parent), and, again, advance progeny by SSD to create 100 F10 generation plants. Based on the information you obtained from your first crossing experiment (Question #4), how many F10 plants would you expect to have black seeds and be resistant to mold? Assume that a toxin produced by the mold fungus has been isolated. Only mold resistant seeds will germinate in the presence of the toxin. Could you use this toxin screening procedure to have segregation distortion work in your favor in the F2 generation? Explain your answer. Info from Question 4 a. P Locus (Seed Color): Hypothesis: The null hypothesis (H₀) is that seed color is controlled by alleles at a single locus. Observed Data: Total white seeds: 45 (resistant plants) + 6 (susceptible plants) = 51 Total black seeds: 7 (resistant…

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