Question

The cells of cyanobacteria and bacteria exhibit similarity in having
A. Plastids
B. Nuclei
C. Centrosomes
D. Naked DNA

Answer 1

Both the cyanobacteria and bacteria do not possess true nucleus but instead they are having nucleoids which is the genetic material of naked DNA.

Complete answer:
There are many similarities between cyanobacteria and bacteria and these are as follows:
-They both are having saprophytic modes of life.
-There is a lack of true cell organelles in both of them.
-There is presence of nucleoid in both instead of having true nucleus and nucleoid is the genetic material of DNA without having nuclear membrane and it is termed as naked DNA.

If we look at options now, option A is Plastids. Plastids are double membrane bound organelles which are present in the cells of plants, algae and some eukaryotic organisms. Plastids are found in cyanobacteria and they are considered endosymbiotic cyanobacteria. But it is not present in bacteria due to which this cannot be the similarity between cyanobacteria and bacteria. Therefore, this option gets eliminated.

Moving to option B i.e., Nuclei. It is the organelle which contains genetic information and it is located at the center of the cell. Both cyanobacteria and bacteria do not possess true nucleus but there is presence of nucleoids in them due to which this option is incorrect as they both do not have nuclei. Therefore, this option gets eliminated.

Option C is Centrosomes. Centrosomes are the organelles made up from an arrangement of two barrel-shaped clusters of microtubules which are called centrioles. This organelle is not present in both cyanobacteria and bacteria but in the question similarity in having that is asked and it is not present in both of them. Hence, this option gets eliminated.

Last option D is Naked DNA. It is the correct option as there is presence of nucleoids instead of true nucleus in both cyanobacteria and bacteria. Nucleoids have genetic material of DNA with the nuclear membrane and that DNA having nuclear membrane is termed as Naked DNA. Since they both possess naked DNA, the cells of cyanobacteria and bacteria exhibit similarity in having naked DNA.

Hence, the correct answer is option (D).
Note: Similarity in cyanobacteria and bacteria is that they both possess naked DNA as they both are having nucleoid instead of true nucleus which is the genetic material of DNA without nuclear membrane i.e., Naked DNA. Therefore, option D i.e., Naked DNA is correct.