All Free Biology MCQs with Answers

2741. How many molecules of RNA are found in HIV:

• A. 2
• B. 3
• C. 4
• D. 5

Explanation: Answer is "2"Explanation: There are two molecules of reverse transcriptase i.e. one molecule is associated with each RNA.

2742. How many molecules of reverse transcriptase are found in HIV:

• A. 2
• B. 3
• C. 4
• D. 5

Explanation: Answer is "2"Explanation: HIV have two identical strands of RNA, each having its own reverse transcriptase molecule.

2743. In infection cycle of HIV, RNA is converted into DNA duplex by:

• A. Replication
• B. Transcription
• C. Reverse transcription
• D. Translation

Explanation: Answer is "Reverse Transcription"Explanation: RNA is converted into DNA by a process called reverse transcription. It is controlled by reverse transcriptase enzyme.

2744. T4 phage consists of:

• A. Head
• B. Tail
• C. Nucleocapsid
• D. Head and tail

Explanation: Answer is "Head and tail"Explanation: It is tadpole shaped with a head consisting up of nucleocapsid and a tail attached with head.

2745. Following are true about head of T4 phage EXCEPT:

• A. Hexagonal structure
• B. Pyramidal structure
• C. Prism shaped structure
• D. An oval structure

Explanation: Answer is "An oval structure"Explanation: The head of bacteriophage is an elongated, pyramidal, hexagonal, prism shaped structure, to which straight tail is attached.The head of T4 phage is not oval. It is a prolate icosahedron, which means that it is shaped like a sphere that has been stretched out along one axis. The head of T4 phage is about 50 nanometers in diameter and 100 nanometers long.

2746. "Two triangular structures with common base" is the description of the structure of _ of T4 phage.

• A. Tail
• B. Head
• C. Collar
• D. Base plate

Explanation: The two triangular structures with a common base that you are referring to are called whiskers. They are located on the collar of T4 phage, which is a ring of proteins that surrounds the base of the tail. The whiskers help T4 phage to attach to the host cell by binding to specific molecules on the cell surface.The whiskers are made up of two identical triangular structures that are connected at their bases. Each triangular structure is made up of about 20 copies of a protein called gp12. The gp12 proteins are arranged in a helix that forms a rigid structure that helps the whiskers to penetrate the host cell.The whiskers are a vital part of the infection process for T4 phage. They allow the phage to attach to the host cell and inject its DNA, which is essential for the phage to replicate and infect new host cells.

2747. Within the head of T4 phage _ molecule is present.

• A. Single-Stranded DNA
• B. Double-Stranded DNA
• C. Single-Stranded RNA
• D. Double-stranded RNA

Explanation: Within the head of T4 phage, a double-stranded DNA molecule is present.Double-stranded DNA (dsDNA) is a molecule of DNA that consists of two complementary strands of nucleotides that are held together by hydrogen bonds. The two strands of dsDNA are arranged in an antiparallel fashion, meaning that the 5' end of one strand is paired with the 3' end of the other strand.The dsDNA in the head of T4 phage is about 150,000 base pairs long. It is tightly packed into a helix that is about 20 nanometers in diameter. The dsDNA is held in place by proteins called capsid proteins. The capsid proteins are arranged in a hexagonal lattice that forms a rigid structure that protects the dsDNA from the environment.

2748. The structure of phage _ is more complex than _.

• A. Head, Tail
• B. Tail, Head
• C. Collar, Base plate
• D. Head, Base plate

Explanation: Answer is "Tail, Head"Explanation: Tail contains two types of proteins whereas head contains only one type of protein.

2749. About the tail of the T4 phage which one is not true:

• A. Core or tube is made up of distinct protein
• B. Core or tube is enclosed in a sheath
• C. Core and sheath are made of the same type of protein
• D. Sheath is made of another type of protein

Explanation: Answer is "Core and sheath are made of same type of protein"Explanation: Core of tail is made up of a rigid and inflexible protein whereas sheath is made up of flexible and contractile protein.The core is the genetic material of the phage, which is made up of DNA. The sheath is a protein coat that surrounds the core and protects it from the environment. The sheath also helps the phage to attach to the host cell.

2750. The volume of the T4 phage is about _ times shorter than that of the host

• A. 01
• B. 10
• C. 100
• D. 1000

Explanation: Answer is "1000"Explanation: The volume of the phage is about 1/1000th of the host.