Free Biodiversity and Variety of Life MCQs with Answers

271. HIV can be transmitted by all of the following sources except:

• A. Intimate sexual contact
• B. Contact with blood
• C. Breast feeding
• D. Saliva

Explanation: Modes of transmission of HIV are blood transfusion, sexual contacts and breast-feeding. Saliva is not the source of transmission of HIV.

272. Uncoating of HIV virion occurs:

• A. Outside the cell
• B. In cytoplasm
• C. In nucleus
• D. At any place

Explanation: Uncoating of HIV occurs in the cytoplasm of the host cell. After fusion with the host cell membrane, the viral capsid is released into the cytoplasm, allowing the viral genome to undergo reverse transcription.

273. Protein of HIV that helps in its fusion with T cell:

• A. gp31
• B. gp120
• C. gp141
• D. gp41

Explanation: In the context of fusion with T cells, gp120 plays a crucial role in the attachment to the CD4 receptor, while gp41 is involved in the subsequent fusion of the viral and host cell membranes, facilitating the entry of the viral genome into the T cell.

274. Common among all viruses during their infection cycles:

• A. DNA Replication in cytoplasm
• B. Translation in cytoplasm
• C. Transcription in nucleus
• D. Reverse transcription in cytoplasm

Explanation: Viruses attack target cells and use biosynthetic machinery (ribosomes: present in cytoplasm) of host for protein synthesis. DNA replication and transcription of different viruses take place in cytoplasm and nucleus of host cells.

275. Receptors proteins present on T helper lymphocytes where an HIV particle binds:

• A. CD4
• B. CD8
• C. CD2
• D. CD1

Explanation: CD means cluster of differentiation. There are many types of CD proteins such as CD4 and CD8 etc. attached to cell membrane of different types of T cells. HIV attaches with CD4 that is part of T helper cell membrane.

276. Which one is not an opportunistic disease related to HIV infection?

• A. Destruction of body immune system
• B. Recurrent pneumonia
• C. Pulmonary tuberculosis
• D. Toxoplasmosis

Explanation: This statement is a general characteristic of HIV infection but not a specific opportunistic disease. HIV gradually destroys the immune system, particularly T helper cells, leading to immunodeficiency.

277. In which step of the life cycle of bateriophage, tail releases enzyme lysozyme?

• A. Attachment
• B. Adsorption
• C. Penetration
• D. Injection

Explanation: In the traditional description of the bacteriophage life cycle, the release of lysozyme occurs during the penetration step. After the bacteriophage attaches to the bacterial cell and injects its genetic material, lysozyme is released to weaken the bacterial cell wall, allowing the injected genetic material to enter the host cell.

278. It is an RNA non-enveloped virus:

• A. Poliovirus
• B. Poxvirus
• C. Influenza virus
• D. Herpes virus

Explanation: So, the correct option for an RNA non-enveloped virus from the given choices is A) Poliovirus.

279. The unifying character of all bacteria:

• A. Peptidoglycan
• B. Conjugation
• C. Haploid
• D. Capsule

Explanation: The correct answer, based on the options provided, is C) Haploid. All bacteria have a single set of chromosomes, which makes them haploid organisms. This characteristic is universal among bacteria.

280. When cocci form a Iong chain of cells then the arrangement is called:

• A. Diplococci
• B. Sarcina
• C. Streptoococci
• D. Staphylococci

Explanation: So, when cocci form a long chain of cells, the arrangement is called "Streptococci."