Describe the 'folded-fiber' model of the mitotic chromosome.

Key Concepts

Mitotic Chromosome Structure

The mitotic chromosome is a highly condensed form of chromatin that becomes visible during cell division. It consists of two sister chromatids joined at a region called the centromere. This structure is essential for the accurate segregation of genetic material into daughter cells during mitosis.

Folded-Fiber Model

The folded-fiber model proposes that chromosomes are composed of a long DNA molecule that is organized into a series of loops or folds. These loops are further compacted and organized by proteins, allowing the chromosome to fit within the confines of the cell nucleus while maintaining the ability to be accessed for gene expression and replication.

Chromatin and Its Levels of Organization

Chromatin is the complex of DNA and proteins found in the nucleus, existing in two forms: euchromatin (less condensed, active in transcription) and heterochromatin (more condensed, generally inactive). The organization of chromatin into higher-order structures, such as the folded-fiber model, is crucial for regulating gene expression and ensuring proper chromosome behavior during cell division.