Life: The Science of Biology
Life: The Science of Biology
11th Edition
ISBN: 9781319010164
Author: David E. Sadava, David M. Hillis, H. Craig Heller, Sally D. Hacker
Publisher: W. H. Freeman
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Chapter 14, Problem 2Q
Summary Introduction

To review:

The reason behind the restoration of the wild-type phenotype after the fusion of two mutant strains.

Given:

Two mutant strains of Neurospora (Leu-1 and Leu-2), the wild-type and the fused type were supplied with different nutrient media and their growth was recorded in Table 1. The presence of growth is indicated by the positive sign (+) and the absence of growth is indicated by the negative sign (−).

Table 1: The results of the growth of different strains of Neurospora in different media.

Types of strains used in the experiment The growth of different strains of Neurospora in different media
Minimal medium Minimal medium+2-isopropylmalate Minimal medium+leucine Minimal medium+3-isopropylmalate Minimal medium+α-ketoisocaproate
Wild type (haploid) + + + + +
Leu-1 (haploid) - - + - +
Leu-2 (haploid) - - + + +
Fused cells (diploid): Leu-1, Leu-2 - + + + +

The following reaction shows the steps involved in the synthesis of leucine in Neurospora (Figure 1).

Life: The Science of Biology, Chapter 14, Problem 2Q

Figure 1

Introduction:

Neurospora is an organism that has a single set of the chromosome (haploid) and is able to grow easily under the laboratory conditions. This is the reason due to which it is used as a model organism. The wild-type strain requires minimal medium to grow because they are able to synthesize the essential amino acids, like leucine on their own. The mutant strains like Leu-1 and Leu-2 are unable to synthesize the leucine and are unable to grow on the minimal medium. When the sexual reproduction occurs between two strains, the wild-type phenotype is restored.

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