A marine biologist prepared chromosome spreads from the embryonic cells of a marine polychaete worm to construct its karyotype.
During the preparation, the cells (normally maintained in seawater) were incubated in a dilute salt solution with a higher (less negative) water potential than the intracellular fluid of the cells. Explain the mechanism by which this treatment facilitates the separation of chromosomes within the cell without causing cell lysis.
To construct the karyotype, the biologist groups the observed chromosomes into homologous pairs. Define what is meant by a homologous pair of chromosomes.
In the marine environment, many species of bacteria coexist with the polychaete worm. State two structural differences between the arrangement of DNA in a prokaryotic bacterium and the DNA in a eukaryotic chromosome of this worm.