What is the Difference Between Chromosome and Chromatid?

The main difference between a chromosome and a chromatid lies in their structure and function. Here are the key differences:

• Definition: A chromosome is a DNA molecule that contains all or part of the genetic material of an organism. A chromatid is one copy of a newly copied chromosome, still attached to the original chromosome by a single centromere.
• Content: A chromosome consists of a single, double-stranded DNA molecule. A chromatid consists of two DNA strands joined together by their centromere.
• Homology: Homologous chromosomes are not identical, as they have different traits, with one copy of the gene coming from each parent. Homologous sister chromatids are identical, as each sister chromatid is an exact copy of the other.
• Stage of Appearance: Chromosomes appear in the M phase of the cell cycle, while chromatids appear in the interphase.
• Function: Chromosomes carry and distribute the genetic material. Chromatids are involved in metabolism and other cellular activities, allowing cells to duplicate.
• Structure: The chromosome has a thin, ribbon-like structure, while the chromatid has a thin, long, and fibrous structure.
• Condensation: Chromosomes are the most condensed form of DNA, with DNA being condensed 10,000 times to form a chromosome. Chromatids are less condensed, with an unraveled condensed structure of DNA, being condensed 50 times to form a chromatid.
• Occurrence: Chromosomes occur throughout the life cycle of cells, while chromatids are only created when the cell undergoes mitosis or meiosis.

Comparative Table: Chromosome vs Chromatid

Here is a table summarizing the differences between chromosomes and chromatids:

Chromosomes are thread-like structures present in the nucleus or nuclear region of the cytoplasm, made up of a single molecule of DNA tightly packed with histone proteins. Chromatids, on the other hand, are the two identical copies or halves of a replicated chromosome, formed during cell division. They are less condensed than chromosomes and have a thin, long fibrous structure.