Where does replication of human chromosome 21 occur?In the nucleus.In the cytoplasm.At the ribosome.In the inner membrane of mitochondria.In the lysosome.

Replication of human chromosome 21 occurs in the nucleus. This is where DNA replication takes place in eukaryotic cells, such as human cells. The process involves the unwinding of the DNA double helix, the synthesis of new strands by the enzyme DNA polymerase, and the reformation of the double helix. This ensures that each new cell has a complete set of chromosomes. The other options listed (cytoplasm, ribosome, inner membrane of mitochondria, lysosome) are not sites of DNA replication.