"Sister chromatids" are:

• A. Genetically identical & attached by a centromere.
• B. Genetically different & attached by a centromere.
• C. Genetically different & attached at the genome.
• D. Genetically identical & attached at the chromosome.

Answer: (A)

Verified step by step guidance

1. Understand the definition of sister chromatids: Sister chromatids are two identical copies of a single replicated chromosome that are connected to each other.
2. Recall that sister chromatids are formed during the S phase of the cell cycle when DNA replication occurs, producing two identical DNA molecules.
3. Recognize that sister chromatids remain attached at a specific region called the centromere, which is crucial for their proper segregation during cell division.
4. Note that because sister chromatids are copies of the same chromosome, they are genetically identical, unlike homologous chromosomes which are similar but not identical.
5. Conclude that the correct description of sister chromatids is that they are genetically identical and attached by a centromere.