The accompanying chromosome diagram represents a eukaryotic chromosome prepared with Giemsa stain. Indicate the heterochromatic and euchromatic regions of the chromosome, and label the chromosome's centromeric and telomeric regions.

Why are expressed genes not found in the telomeric region of chromosomes? <>

Key Concepts

Euchromatin and Heterochromatin

Euchromatin is a less condensed form of chromatin that is actively involved in transcription, allowing genes to be expressed. In contrast, heterochromatin is tightly packed and generally transcriptionally inactive, serving structural roles in the chromosome. Understanding the distinction between these two types of chromatin is essential for identifying regions of gene expression within a chromosome.

Centromere and Telomere

The centromere is the region of a chromosome where sister chromatids are joined and is crucial for proper chromosome segregation during cell division. Telomeres are repetitive nucleotide sequences at the ends of chromosomes that protect them from degradation and prevent fusion with neighboring chromosomes. Both regions are typically devoid of expressed genes due to their structural and protective functions.

Gene Expression Regulation

Gene expression regulation involves mechanisms that control the transcription of genes, determining when and how much of a gene product is made. In eukaryotic cells, expressed genes are often found in euchromatic regions, while telomeric regions are generally silenced to maintain chromosome stability. This regulation is vital for cellular function and development, explaining why expressed genes are absent from telomeric regions.