Question

Prokaryotic genetic material is
A. Linear DNA + histone
B. Circular DNA + histone
C. Linear DNA + without histone
D. Circular DNA + without histone

Answer 1

Hint: A prokaryote is a simple, single-celled organism that lacks membrane-bound organelles. The prokaryotic cells are not divided up on the inside by membrane walls, but consist instead of a single open space.

Complete answer:
Prokaryotes are organisms whose cells lack a nucleus and other organelles. Most prokaryotes are small, single-celled organisms that have a relatively simple structure. The absence of a nucleus and other membrane-bound organelles differentiates prokaryotes from another class of organisms called eukaryotes. Prokaryotes are divided into two distinct groups: the bacteria and the archaea.
Cell size: Prokaryotic cells range from 0.1 to 5.0 micrometers in diameter.
Components of prokaryotic cells:
Plasma membrane is an outer covering separating cell’s internal structure from its surrounding environment.
Cytoplasm consists of jelly-like cytosol inside the cell along with cellular structures suspended in it.
DNA is the genetic material of the cell.
Ribosomes for synthesizing proteins.
Most of the prokaryotic DNA is found in the central region of cell known as the nucleoid, consisting of a single large loop called a circular chromosome. Many of them also carry small, circular DNA molecules called plasmids, which are distinct from the chromosomal DNA. Most bacteria are, however, surrounded by a rigid cell wall made out of peptidoglycan, a polymer composed of linked carbohydrates and small proteins. Cell wall provides an extra layer of protection, helps the cell maintain its shape, and prevents dehydration. Some of the bacteria also have an outermost layer of carbohydrates known as capsule which is sticky and helps the cell attach to surfaces in its environment. Some bacteria have fimbriae which are hair-like structures used for attachment to host cells and other surfaces. Bacteria may also have rod-like structures known as pili which help the bacteria to transfer DNA molecules to other bacteria.
Nucleoid: Nucleoid is an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material. The genome of prokaryotic organisms generally is a circular, double-stranded piece of DNA, of which multiple copies may exist at any time. The length of a genome varies widely.
Genophore: A genophore is the DNA of a prokaryote. It is commonly referred to as a prokaryotic chromosome but lacks chromatin. It is compacted through a mechanism known as supercoiling. The genophore is circular in a large number of prokaryotes. It’s circular nature allows replication to occur without telomeres.
Therefore, the correct option is d, Circular DNA + without histone.

Note: Supercoiling: DNA supercoiling refers to the winding of a DNA strand. It is important for compacting DNA. Also, certain enzymes such as topoisomerases change DNA topology and facilitate functions such as DNA replication or transcription. The DNA of most organisms is negatively supercoiled.
Supercoiled DNA forms two structures; a plectoneme or a toroid, or a combination of both. Negatively supercoiled DNA molecule produces either a one-start left-handed helix (toroid), or a two-start right-handed helix with terminal loops (plectoneme). In larger molecules, hybrid structures are formed – a loop on a toroid can extend into a plectoneme. If all the loops on a toroid extend, it becomes a branch point in the plectonemic structure.