In a study of Drosophila, two normally active genes, w⁺ (wild-type allele of the white-eye gene) and hsp26 (a heat-shock gene), were introduced (using a plasmid vector) into euchromatic and heterochromatic chromosomal regions, and the relative activity of each gene was assessed [Sun et al. (2002)]. An approximation of the resulting data is shown in the following table. Which characteristic or characteristics of heterochromatin are supported by the experimental data? Gene Activity (relative percentage) _ Euchromatin Heterochromatin hsp26 100% 31% w⁺ 100% 8%

Verified step by step guidance

1. Identify the key difference between euchromatin and heterochromatin: Euchromatin is generally more transcriptionally active, while heterochromatin is more condensed and less transcriptionally active.
2. Examine the gene activity data for both euchromatin and heterochromatin: hsp26 shows 100% activity in euchromatin and 31% in heterochromatin, while w⁺ shows 100% activity in euchromatin and 8% in heterochromatin.
3. Compare the relative gene activity in euchromatin versus heterochromatin: Both genes show reduced activity in heterochromatin compared to euchromatin.
4. Consider the implications of reduced gene activity in heterochromatin: This suggests that heterochromatin is less accessible for transcription, supporting its role in gene silencing or reduced gene expression.
5. Conclude which characteristics of heterochromatin are supported: The data supports that heterochromatin is associated with reduced gene expression and transcriptional silencing.

Key Concepts

Euchromatin vs. Heterochromatin

Euchromatin and heterochromatin are two forms of chromatin found in eukaryotic cells. Euchromatin is less condensed, transcriptionally active, and accessible for gene expression, while heterochromatin is more tightly packed, transcriptionally inactive, and often associated with gene silencing. Understanding these differences is crucial for interpreting gene activity data in the context of chromosomal regions.

Gene Expression Regulation

Gene expression regulation refers to the mechanisms that control the transcription and translation of genes, influencing how much of a gene product is produced. Factors such as chromatin structure, transcription factors, and epigenetic modifications play significant roles in determining whether genes are active or silenced. The experimental data highlights how the chromatin environment affects the expression levels of the introduced genes.

Heat-Shock Response

The heat-shock response is a cellular mechanism activated by stress conditions, such as elevated temperatures, leading to the expression of heat-shock proteins like hsp26. These proteins help protect and refold damaged proteins, ensuring cell survival. The reduced activity of hsp26 in heterochromatin suggests that the chromatin state can influence the cell's ability to respond to stress, which is a key characteristic of heterochromatin.