Question

What genetic process is occurring in a puff of a polytene chromosome?

Short answer

Answer: The genetic process that occurs in a puff of a polytene chromosome is gene transcription.

Step-by-step solution

Understand Polytene Chromosomes

Polytene chromosomes are large, multiple copies of DNA that are bundled together within a single chromosome. These bundles are known as chromonemata and are most commonly observed in the salivary glands of Drosophila (fruit flies) during the interphase stage of the cell cycle. Polytene chromosomes have uniquely identifiable banding patterns in which some regions are denser and others are thinner. The thin regions, called "puffs," play a crucial role in the genetic process.

Identify the Role of Puffs

Puffs are regions of the polytene chromosome where the chromosomal material has "puffed-up" or decondensed, allowing the DNA within them to be more accessible. Puffs are generally associated with active gene transcription, which is the genetic process by which a segment of DNA is used as a template to create a molecule of RNA that will later be translated into a protein.

Understanding Gene Transcription

Gene transcription is the first step in gene expression and occurs when RNA polymerase, an enzyme, binds to a specific region of the DNA, called the promoter. This promoter region signals the beginning of the gene to be transcribed. Once RNA polymerase binds to the promoter, it begins to unwind the DNA, separating the two strands, and starts to synthesize RNA using one strand of DNA as a template. As the RNA strand grows, it follows the so-called genetic code that ultimately determines which protein will be produced.

Identify the Genetic Process in a Puff

Since puffs are regions of the polytene chromosome where gene transcription takes place, the genetic process that occurs in a puff of a polytene chromosome is gene transcription. This process is crucial for the production of proteins, which are essential for the growth, development, and proper functioning of an organism.