Sister Chromatids

Definition

Sister chromatids are two identical copies of a single chromosome, joined together at a region called the centromere. They are crucial during cell division, as they ensure that each daughter cell receives an identical set of chromosomes. The formation and separation of sister chromatids play significant roles in processes like recombination and homologous repair, as well as in the accurate distribution of genetic material during mitosis and meiosis.

5 Must Know Facts For Your Next Test

1. Sister chromatids are formed during the S phase of interphase when DNA is replicated.
2. During mitosis, sister chromatids are separated and pulled to opposite poles of the cell to ensure that each daughter cell gets a complete set of chromosomes.
3. In meiosis, sister chromatids are separated during both meiosis I and meiosis II, leading to the formation of haploid gametes.
4. Sister chromatids are important for genetic stability, as any errors in their separation can lead to aneuploidy, where daughter cells have an abnormal number of chromosomes.
5. During homologous recombination, sister chromatids can exchange genetic material, increasing genetic diversity in the resulting gametes.

Review Questions

• How do sister chromatids ensure accurate chromosome distribution during cell division?
  • Sister chromatids ensure accurate chromosome distribution by being connected at the centromere and aligning along the metaphase plate during mitosis. This alignment allows spindle fibers to attach to each chromatid and pull them apart during anaphase. This process guarantees that each daughter cell receives one copy of each chromatid, maintaining the correct chromosome number.
• Discuss the role of sister chromatids in homologous recombination and how this impacts genetic variation.
  • Sister chromatids play a vital role in homologous recombination by providing identical genetic sequences that can exchange segments of DNA during meiosis. This exchange increases genetic variation by creating new combinations of alleles, which contributes to diversity in gametes. Such variation is essential for evolution and adaptation in populations over time.
• Evaluate the consequences of improper separation of sister chromatids during cell division and its implications for an organism.
  • Improper separation of sister chromatids can lead to aneuploidy, where cells end up with too many or too few chromosomes. This condition can cause serious health issues, such as cancer or genetic disorders like Down syndrome. The resulting imbalance in chromosome numbers can disrupt normal cellular functions and development, highlighting the importance of accurate chromatid separation for organismal health.

Related terms

Chromosome: A long DNA molecule with part or all of the genetic material of an organism, visible during cell division.

Centromere:

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

Homologous Chromosomes: Pairs of chromosomes containing the same genes but possibly different alleles, one inherited from each parent.