Are sister chromatids completely identical to each other?

Sister chromatids are indeed identical to each other in terms of their DNA sequence and alleles. They are the result of DNA replication during the S phase of the cell cycle, which creates two copies of each chromosome that are attached at a region called the centromere. These chromatids carry the same genetic information, which is crucial for accurate chromosome segregation during cell division.

In the context of genetic material, the term "identical" means that both sister chromatids will have the same alleles at corresponding loci because they originate from the same parent chromosome prior to replication. This identical nature ensures that when the sister chromatids are separated into daughter cells during mitosis, each new cell receives an accurate copy of the genetic material.

It’s important to differentiate between sister chromatids and homologous chromosomes. Homologous chromosomes are similar, but they originate from different parental sources and can carry different alleles. This is relevant when considering genetic variation during processes like meiosis, where homologous chromosomes may contain different versions of a gene.

In summary, sister chromatids, being direct copies of each other produced during DNA replication, are completely identical to one another. This identity is essential for maintaining genetic consistency through cellular division.