How are sister chromatids different from homologous chromosomes?

Sister chromatids are identical copies of a single chromosome, while homologous chromosomes are similar but not identical pairs of chromosomes.

Sister chromatids are produced during the S phase of the cell cycle when a chromosome is replicated. This replication results in two identical copies of the chromosome, which are attached at a point called the centromere. These identical copies are known as sister chromatids. They share the exact same genetic information because they are produced by the replication of a single chromosome. During cell division, these sister chromatids are separated, and each new cell receives one of the chromatids.

On the other hand, homologous chromosomes are a pair of chromosomes, one from each parent, that are similar in size, shape, and gene content, but are not identical. They carry the same genes in the same order, but the specific versions of these genes (known as alleles) may differ between the two chromosomes. For example, one chromosome might carry a gene for blue eyes, while its homologue carries a gene for brown eyes. During meiosis, homologous chromosomes pair up and exchange segments of DNA in a process known as crossing over. This leads to genetic variation in the offspring.

In summary, while both sister chromatids and homologous chromosomes are involved in cell division and genetic inheritance, they are different in their origin and genetic content. Sister chromatids are identical copies of a single chromosome, produced by replication during the cell cycle. Homologous chromosomes, however, are similar but not identical pairs of chromosomes, one from each parent, carrying the same genes but potentially different alleles.