Question Video: Recalling Facts about Plasmids and Chromosomal Prokaryotic Genetic Material | Nagwa Question Video: Recalling Facts about Plasmids and Chromosomal Prokaryotic Genetic Material | Nagwa

Question Video: Recalling Facts about Plasmids and Chromosomal Prokaryotic Genetic Material Biology • Third Year of Secondary School

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Which of the following statements is true? The plasmid is not able to replicate. Circular DNA exists only in prokaryotes. [A] Neither statement is true. [B] Both statements are true. [C] The first statement only is true. [D] The second statement only is true.

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Video Transcript

Which of the following statements is true? The plasmid is not able to replicate. Circular DNA exists only in prokaryotes. (A) Neither statement is true. (B) Both statements are true. (C) The first statement only is true. (D) The second statement only is true.

Prokaryotes are single-celled organisms that are mainly distinguished from eukaryotes by the absence of membrane-bound organelles. In most prokaryotes, the majority of prokaryotic DNA can be found as chromosomal DNA. Prokaryotic chromosomal DNA often exists as a single circular chromosome and is not contained in a nucleus. Rather, it is concentrated in an area of the cell called the nucleoid.

In contrast, eukaryotes contain their genetic material within a nucleus, often in the form of multiple linear chromosomes. However, eukaryotes also have additional genetic material that can be found in certain organelles, including the mitochondria and chloroplasts, both of which are involved in producing energy for the cell. These organelles are believed to have evolved from prokaryotes and therefore also have circular DNA.

So, we know that circular DNA exists in eukaryotes as well as prokaryotes, and this statement is not true. Prokaryotes also contain DNA that’s separate from the chromosomal DNA, but this DNA is not contained within an organelle. This DNA is called plasmid DNA.

Plasmids are pieces of circular DNA that contain different genes that can allow the prokaryote to grow in different environments. Plasmid DNA replicates independently of chromosomal DNA and can be shared with other prokaryotes in some situations. So, we now know that this first statement is also incorrect.

Therefore, the correct option for this question is given by answer choice (A). Neither statement is true.

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