Sister chromatids

Definition

Sister chromatids are identical copies of a single chromosome that are connected by a centromere and are crucial during cell division. They form during the S phase of the cell cycle, when DNA is replicated, ensuring that each new cell receives an identical set of chromosomes. Understanding sister chromatids is vital for grasping how genetic information is accurately distributed during both mitosis and meiosis.

5 Must Know Facts For Your Next Test

1. Sister chromatids are formed during DNA replication in the S phase of the cell cycle, resulting in two identical copies of each chromosome.
2. During mitosis, sister chromatids separate and move to opposite poles of the cell to ensure that each daughter cell receives an identical set of chromosomes.
3. In meiosis, sister chromatids are separated during the second meiotic division, leading to the formation of gametes with half the original chromosome number.
4. Each sister chromatid contains identical genetic information due to the replication process, which is essential for maintaining genetic stability.
5. The proper separation of sister chromatids is critical; errors can lead to aneuploidy, a condition where cells have an abnormal number of chromosomes.

Review Questions

• How do sister chromatids contribute to genetic stability during cell division?
  • Sister chromatids contribute to genetic stability by ensuring that each daughter cell receives an exact copy of the parent's genetic material during cell division. When DNA replicates in the S phase, sister chromatids are formed and held together by a centromere. During mitosis or meiosis, these sister chromatids separate accurately to prevent any loss or duplication of genetic information, which is essential for maintaining proper chromosome number in daughter cells.
• Discuss the role of sister chromatids during meiosis and how their separation affects genetic diversity.
  • During meiosis, sister chromatids play a critical role in generating genetic diversity through their separation during two rounds of division. In the first meiotic division, homologous chromosomes separate, while sister chromatids remain together. In the second division, it is the sister chromatids that separate. This process not only ensures that gametes have half the number of chromosomes but also allows for crossing over between homologous chromosomes earlier in meiosis, leading to new combinations of genes and increased genetic variation in offspring.
• Evaluate the consequences of errors in sister chromatid separation during cell division and their implications for health.
  • Errors in sister chromatid separation can lead to aneuploidy, where cells end up with an abnormal number of chromosomes. This can cause serious health issues such as cancer or genetic disorders like Down syndrome, which arises from an extra copy of chromosome 21. When sister chromatids do not separate correctly, it disrupts normal development and function at both cellular and organismal levels, highlighting the importance of precise mechanisms in ensuring accurate chromosome segregation.

Related terms

Chromosome: A structure made of DNA and protein that contains genetic information, found in the nucleus of eukaryotic cells.

Centromere:

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

Mitosis: The process of cell division that results in two identical daughter cells, each with the same number of chromosomes as the parent cell.