In this chapter, we have focused on chromosomal mutations resulting from a change in number or arrangement of chromosomes. In our discussions, we found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, what answers would you propose to the following fundamental questions? How do we know that the mutant Bar-eye phenotype in Drosophila is due to a duplicated gene region rather than to a change in the nucleotide sequence of a gene?

Key Concepts

Gene Duplication

Gene duplication is a process where a segment of DNA is copied, resulting in multiple copies of a gene within the genome. This can lead to phenotypic variations, such as the Bar-eye phenotype in Drosophila, as the extra gene copies can alter gene expression and function. Understanding this mechanism is crucial for distinguishing between mutations caused by duplication versus those caused by changes in nucleotide sequences.

Phenotypic Expression

Phenotypic expression refers to the observable traits or characteristics of an organism, which result from the interaction of its genotype with the environment. In the case of the Bar-eye phenotype, the specific eye shape and color are direct results of genetic alterations. Analyzing how these traits manifest can help determine whether they arise from gene duplication or nucleotide sequence changes.

Molecular Techniques in Genetics

Molecular techniques, such as PCR, sequencing, and comparative genomic hybridization, are essential for analyzing genetic material. These methods allow researchers to identify specific mutations, including gene duplications, and to differentiate them from point mutations in nucleotide sequences. Utilizing these techniques provides the evidence needed to support claims about the genetic basis of phenotypic traits like the Bar-eye phenotype.