Most Repeated MDCAT Biology: Biodiversity | Variety of Life MCQs

Explanation

The correct answer is c. Virion. A virion is the complete, mature, and infectious virus particle, consisting of the viral genome (DNA or RNA) enclosed within a protective protein coat called the capsid. Unlike the genome or capsid alone, which are only parts of a virus, the virion represents the fully assembled unit capable of infecting host cells.

Explanation

Parvoviruses are a group of viruses that carry a single-stranded DNA genome. They are among the smallest DNA viruses and typically infect animals, including humans.

Explanation

Bacteriophages typically have tail fibers attached to the end plate. These tail fibers help the phage attach to specific receptors on the surface of the bacterial host cell. There are six long tail fibers attached to the end plate of a bacteriophage.

Explanation

During the process of baking, anaerobic respiration is used by yeast to convert sugars in dough into carbon dioxide gas, which causes the dough to rise. So, option D is selected.

Explanation

HIV (Human Immunodeficiency Virus) is primarily transmitted through several key routes. The most common mode of transmission is through unprotected sexual contact with an infected individual, where the virus can enter the body through mucous membranes. Additionally, sharing needles or syringes among intravenous drug users poses a significant risk, as it allows for direct blood-to-blood contact. HIV can also be transmitted from an infected mother to her child during childbirth or breastfeeding, highlighting the importance of preventive measures for pregnant women living with HIV.

Explanation

The scientific name for humans, Homo sapiens, follows the binomial nomenclature system, which consists of two parts: the genus and the species. In this system, the genus name is capitalized and the species name is lowercase, both in italics. The other options are incorrect because they do not reflect the components of this naming system. 'Genus and family', 'family and order', 'order and class', and 'genus and class' do not align with the binomial naming convention.

Explanation

Malaria is not a viral disease and is caused by the protozoan Plasmodium. All other options are viral infections that include AIDS caused by the HIV virus, influenza caused by the influenza virus, chickenpox caused by the varicella-zoster virus (VZV), and rabies caused by the rabies lyssavirus.

Explanation

Lacking envelope: As indicated by their name, un-enveloped plus-strand RNA viruses lack envelopes and consist only of a nucleic acid core capsid surrounded by protein viruses.

Explanation

Hepatitis B spreads through contact with infected body fluids. This includes blood, serum, saliva, breast milk, and it can also be passed on through sexual contact.

Explanation

Tay-Sachs disease is a genetic disorder where the enzyme Hexosaminidase A is absent. It causes progressive nerve damage, loss of motor skills, blindness, seizures, and death usually by age 3.

Explanation

The concept of alternation of generations in plants involves a life cycle that alternates between a diploid sporophyte stage and a haploid gametophyte stage. This cycle allows plants to utilize both sexual and asexual reproduction, which is crucial for adapting to diverse environmental conditions. Sexual reproduction introduces genetic variation, while asexual reproduction enables rapid colonization. This adaptability is essential for plant survival, especially since plants are immobile and must cope with changing environments. Thus, the primary purpose of this cycle is to promote survival.

Explanation

Live attenuated vaccines are designed to provoke a strong immune response by using a weakened form of the virus. They are used for diseases like measles, mumps, and polio. However, cholera and rabies vaccines do not typically use live attenuated strains. Cholera vaccines are usually inactivated, while rabies vaccines are inactivated or recombinant. Understanding the specific vaccines available for each disease is crucial for answering this question correctly.

Explanation

The Human Immunodeficiency Virus (HIV) is a retrovirus, which means its genome is composed of two single-stranded RNA molecules. The HIV genome consists of:- 2 copies of single-stranded RNA (ssRNA)- 9 genes encoding 15 proteins- Approximately 9,700 nucleotides in totalHIV's RNA genome is converted to DNA through reverse transcription, a process facilitated by the enzyme reverse transcriptase. This DNA is then integrated into the host cell's genome, allowing the virus to replicate.

Explanation

Viruses are not classified based on the presence or absence of a cell membrane because:- Viruses do not have a cell membrane like cellular organisms do. Instead, they have a protein coat called a capsid that surrounds their genetic material.- Some viruses have an envelope, which is a lipid bilayer derived from the host cell membrane, but this is not a universal characteristic among viruses.

Explanation

The capsule is an additional covering that surrounds the cell wall of some bacteria, providing protection against:- Phagocytosis (engulfment by host cells)- Desiccation (drying out)- Antibiotics and other antimicrobial agentsThe capsule is composed of polysaccharides (complex sugars) and can be found in both Gram-positive and Gram-negative bacteria.