Chapter 25, Problem 1MC

Summary Introduction

Introduction:

Viruses are the pathogenic microorganisms that cause many hazardous diseases in living forms. All viruses use their genetic material either DNA or RNA to transmit viral components into host cells. There are four types of RNA viruses: positive and negative single stranded RNA, double stranded RNA and retroviruses.

Answer to Problem 1MC

Correct answer:

A segmented genome is one that has more than one strand of nucleic acid. Therefore, option (a) is correct.

Option (a) is given as “more than one strand of nucleic acid”.

Explanation of Solution

Justify reason for the correct statement:

Viruses are classified on the basis of types of RNA they have. There are some RNA viruses that contain more than single molecule of RNA which means that they contain segmented genome. The viruses with negative sense single stranded RNA consists of segmented genome as their genome is fragmented into more than one molecules of nucleic acid and are packed as different segments of RNA.

Hence, option (a) is correct.

Justify reasons for the incorrect statements:

Option (b) is given as “double stranded RNA”.

Double stranded RNA is not a segmented genome. Segmented genome have more than one molecule of RNA and not double strands of RNA. Hence, it is a wrong answer.

Option (c) is given as “both RNA and DNA strands”.

Both RNA and DNA strand does not contribute to the property of a segmented genome. Hence, it is a wrong answer.

Option (d) is given as “both $\text{+ssRNA}$ and $\text{-ssRNA}$ molecules”.

A segmented genome have more than one molecule of RNA and is found in negative sense single stranded RNA. It does not have both positive and negative sense RNA. Hence, it is a wrong answer.

Hence, options (b), (c), and (d) are incorrect.

Conclusion

Flu viruses like Bunyaviridae and Arenaviridae which have negative sense single stranded RNA have fragmented genome packed into different segments of RNA called segmented genome.