Explain how the following mutations would affect transcription of the yeast GAL1 gene in the presence of galactose.

A point mutation in the GAL1 core promoter that alters the sequence of the TATA box.

Key Concepts

TATA Box

The TATA box is a conserved DNA sequence found in the core promoter region of many eukaryotic genes, including the GAL1 gene in yeast. It is typically located about 25-30 base pairs upstream of the transcription start site and serves as a binding site for transcription factors and RNA polymerase II. Mutations in the TATA box can disrupt the formation of the transcription initiation complex, leading to altered levels of gene expression.

Transcription Regulation

Transcription regulation refers to the mechanisms that control the rate and timing of gene expression. In yeast, the presence of galactose activates specific transcription factors that enhance the transcription of the GAL1 gene. A mutation in the TATA box may hinder the binding of these factors, thereby affecting the gene's transcription in response to galactose availability.

Point Mutation

A point mutation is a change in a single nucleotide base pair in the DNA sequence. This type of mutation can lead to various effects, including silent, missense, or nonsense mutations, depending on its location and nature. In the context of the GAL1 gene, a point mutation in the TATA box could significantly impact the binding affinity of transcription machinery, ultimately influencing the gene's expression levels in the presence of galactose.