Answer to Question #27297 in Molecular Biology for sheena

Question

what are sister chromatids?

Answer 1

Sister chromatids are two identical structure elements of chromosome. They are joined at the centromere and formed after replication of chromosome during S-phase of interphase. The DNA in sister chromatids are identical, if no crossing over and synapsis occurs.
In contrast, homologous chromosomes usually do not have identical alleles at all loci, because they are inherited from different parents and therefore are not derived from the same DNA molecule.