Chromatid

Definition

A chromatid is one half of a duplicated chromosome, formed during the cell division process. When a cell prepares to divide, its chromosomes replicate and each chromosome consists of two sister chromatids held together at a region called the centromere. These sister chromatids separate during mitosis, ensuring that each new daughter cell receives an identical set of chromosomes, which is crucial for maintaining genetic stability.

5 Must Know Facts For Your Next Test

1. During the S phase of the cell cycle, each chromosome is replicated to form two identical sister chromatids, which remain attached at the centromere until mitosis.
2. In mitosis, sister chromatids are separated and pulled to opposite poles of the dividing cell during anaphase, ensuring each daughter cell gets one copy of each chromatid.
3. Chromatids can be considered identical copies of a chromosome until crossing over occurs in meiosis, where genetic material is exchanged, leading to genetic variation.
4. The proper separation of chromatids during cell division is critical; errors in this process can lead to aneuploidy, which is the presence of an abnormal number of chromosomes in a cell.
5. Chromatids are only visible under a microscope during specific stages of the cell cycle, particularly during prophase and metaphase when chromosomes condense.

Review Questions

• How do chromatids ensure genetic stability during the cell cycle?
  • Chromatids play a crucial role in maintaining genetic stability by ensuring that each daughter cell receives an identical set of chromosomes. During the S phase, chromosomes are replicated into two sister chromatids that are held together at the centromere. When mitosis occurs, these sister chromatids are separated and distributed to two new daughter cells, ensuring that genetic information is accurately passed on and preserved across generations.
• What happens to chromatids during mitosis and why is their separation important?
  • During mitosis, specifically in anaphase, the sister chromatids are pulled apart by spindle fibers towards opposite ends of the cell. This separation is vital because it guarantees that each new daughter cell receives one complete set of chromosomes. If chromatids do not separate correctly, it can result in daughter cells with missing or extra chromosomes, leading to potential diseases or developmental issues.
• Discuss the role of crossing over in meiosis regarding chromatids and genetic variation.
  • Crossing over occurs during prophase I of meiosis when homologous chromosomes exchange segments of genetic material. This process leads to chromatids that are no longer identical but instead carry different combinations of genes. The result is increased genetic variation among gametes, which is essential for evolution and adaptation in populations. Understanding how crossing over modifies chromatids helps clarify how sexual reproduction contributes to genetic diversity.

Related terms

Centromere:

The constricted region of a chromosome where sister chromatids are joined together and where spindle fibers attach during cell division.

Mitosis: A type of cell division that results in two genetically identical daughter cells from a single parent cell, involving processes such as chromatid separation.

Chromosome: A structure made of DNA and protein that contains genetic information, existing as a single strand or as two sister chromatids during the cell cycle.