Question

if this the structure of chromosome.
Then why they appear single (separate) in the case of human chromosomes

Answer 1

Answer:

In the case of human chromosome they appear to be seperate as humans contains centrioles which plays an important role in the seperation of chromosomes.

Answer 2

Answer:

Chromosome segregation is the process in eukaryotic organisms in which two sister chromatids formed as a consequence of DNA replication, or paired homologous chromosomes, separate from each other and migrate to opposite poles of the nucleus. This occurs in any of the cell division process i.e. meiosis or mitosis. Hence they appear as single.