question_answer 49)

  The genomic content of the nucleus is constant for a given species where as the extra chromosomal DNA is found to be variable among the members of a population. Explain.

Answer:

                  In bacteria, additional to the genomic DNA, small circular DNA molecules are present incytoplasm. These small molecules are called plasmids. They confer unique phenotypiccharacter to bacteria, i.e., resistance to antibiotics. It is also used to monitor bacterialtransformation with foreign DNA. In eukaryotes, the extra DNA molecules are present in chloroplast (stroma) and mitochondria (matrix). Because of the presence of this DNA molecule, they are treated as self autonomous organelles. In case of highly active organism, the DNA extra chromosomalis found to be more as compared to the less active ones.