Question

A prokaryote with linear DNA is
(a)Chlamydia
(b)Mycoplasma
(c)Bacterium
(d)Cyanobacterium

Answer 1

Hint: linear DNA chromosome is one with two terminal ends that aren't bound with each other into a complete ring. Bacteria and cyanobacteria both contain circular DNA with plasmid areas. Chlamydial DNA is ring-shaped with a nucleus. Mycoplasma has naked genetic material that is a singular Duplex of DNA.

Complete answer:
Most prokaryotic organisms harbor minimal genetic material or even a single DNA molecule, or a chromosome formed of circular DNA. The prokaryotic DNA is not inside the nucleus but rather is present in a central area called the nucleoid, which lacks the surrounding nuclear membrane. Many prokaryotes also carry small, circular DNA molecules called plasmids which play an important part in genetic transport.
The Mycoplasmal DNA is an exception for this as it contains an uncovered duplex strand of DNA which is linear and not ring-shaped as other prokaryotes.

Additional Information: The presence of linear DNA in eukaryotes and a ring-shaped DNA in prokaryotes suggests the evolution of Eukaryotic DNA from the Prokaryotic one, such that due to continuous mutations and repetition of genes among generations, which caused the DNA to lose the ligation property and thus prevented it to get back to a circular shape.
 This supports the fact that eukaryotes are direct descendants of prokaryotic organisms.
A circular DNA is one that forms a closed loop that has no terminal edges. The examples of circular DNA are plasmids, circular bacterial DNA, mitochondrial DNA, etc.
So, the correct answer is 'Mycoplasma'

Note: In about all mammals, the mitochondrial DNA is inherited from the maternal side this is because the mitochondria from the sperm are destroyed by the ova after fertilization. Human mitochondrial DNA is double-stranded circular DNA.