Human Health and Diseases

The correct answer regarding the AIDS causative agent HIV (Human Immunodeficiency Virus) is:

Option D: HIV is an enveloped virus that contains two identical molecules of single-stranded RNA and two molecules of reverse transcriptase.

Explanation:

HIV is indeed an enveloped virus, which means it has a lipid membrane surrounding its capsid. This envelope is derived from the host cell's membrane and contains proteins necessary for the virus to attach and enter new host cells. Inside the envelope, HIV has a core structure that carries its genetic material and enzymes essential for its replication. The genetic material of HIV is composed of two identical molecules of single-stranded RNA. This characteristic is crucial for its replication process and is a hallmark of retroviruses, the family to which HIV belongs.

The presence of reverse transcriptase, an enzyme carried by HIV, is also a defining feature of retroviruses. This enzyme allows the virus to reverse transcribe its RNA genome into DNA once it has entered a host cell. The newly formed viral DNA can then integrate into the host cell's genome, where it can lie dormant or be used to produce new viral particles. HIV carries two molecules of reverse transcriptase, which is consistent with its need to reverse transcribe both of its RNA strands into DNA.

Therefore, options A, B, and C do not accurately describe HIV:

Option A incorrectly states that HIV is an unenveloped retrovirus, while it is, in fact, enveloped.

Option B is close but misses the detail that HIV contains two, not one, molecules of single-stranded RNA, and similarly, contains two molecules of reverse transcriptase, not just one.

Option C incorrectly suggests that HIV does not evade the immune system. In reality, HIV has evolved multiple strategies to avoid and undermine the host's immune response, contributing to its ability to cause long-term infections.

Entamoeba histolytica is a parasitic protozoan that causes amoebiasis. It primarily affects the colon, where it can cause a range of symptoms from mild diarrhea to severe dysentery. The active, trophozoite form of Entamoeba histolytica feeds on various components in the colon.

The correct answer is:

Option D: erythrocytes, mucosa and submucosa of colon

This is because the trophozoites of Entamoeba histolytica invade the mucosal lining of the colon, leading to ulceration and tissue destruction. They feed on the mucosa and submucosa tissues. Additionally, the trophozoites can ingest erythrocytes (red blood cells), which contribute to their growth and proliferation.

The trophozoite stage is particularly harmful because it can cause significant damage to the host tissues, leading to clinical symptoms and complications associated with amoebiasis.

Let's evaluate each of the statements for accuracy:

(A) Colostrum is recommended for the new born because it is rich in antigen.

This statement is partially correct but is somewhat misleading. Colostrum, the first form of milk produced by mammals immediately following delivery of the newborn, is indeed recommended for newborns, but not merely because it is rich in antigens. It contains a variety of beneficial components like antibodies (especially IgA), growth factors, and nutrients. The antibodies are crucial for passive immunity which protects the infant from infections during the early days of life. Therefore, the rationale behind recommending colostrum is not just because it is 'rich in antigen' but because it contains antibodies and other immune components essential for the newborn's defense.

(B) Chikungunya is caused by a Gram-negative bacterium.

This statement is false. Chikungunya is not caused by a bacterium at all; rather, it is a viral disease caused by the Chikungunya virus, which is transmitted to humans by mosquitoes, namely Aedes aegypti and Aedes albopictus. The categorization of bacteria as Gram-negative or Gram-positive is based on their cell wall composition and staining properties, which are irrelevant to viruses like the Chikungunya virus.

(C) Tissue culture has proved useful in obtaining virus-free plants.

This statement is true. Tissue culture techniques can be used to produce virus-free plants by culturing tissues from plants that are infected with a virus, and then using a technique called meristem culture, which often results in the production of new, virus-free plants. This is an important practice in agriculture and horticulture for maintaining the health and productivity of crops.

(D) Beer is manufactured by distillation of fermented grape juice.

This statement is false. Beer is usually made from the fermentation of cereal grains, primarily barley, although other grains can be used. The production of beer involves malting, mashing, boiling, fermenting, conditioning, filtering, and packaging. Distillation is not a part of the beer brewing process; it is a process used in the production of spirits. Furthermore, fermented grape juice results in wine, not beer.

Considering the above explanations: statement (B) is unquestionably wrong; statement (D) is also wrong; and, while statement (A) contains an element of truth, the wording is misleading and could be considered incorrect for the purpose of this question. Therefore, it is reasonable to conclude that:

Three out of the four given statements are wrong, which corresponds with Option D: Three.

The correct answer is: Option A - Fungi.

Ringworm, also known as tinea, is not caused by a worm but by a fungal infection of the skin. It is called "ringworm" because the infection can cause a ring-shaped, red, itchy rash on the skin. The fungi that cause ringworm are known as dermatophytes, and they live on the dead outer layer of skin, hair, and nails. They thrive in warm, moist environments, which is why they are commonly found in places like locker rooms and swimming pools and can be spread through direct contact with an infected person or animal or through contact with contaminated objects or surfaces.

There are different types of fungi that can cause ringworm, including Trichophyton, Microsporum, and Epidermophyton. These fungi can infect various parts of the body and lead to conditions such as athlete's foot (tinea pedis), jock itch (tinea cruris), scalp ringworm (tinea capitis), and ringworm of the body (tinea corporis).

Ringworm treatment usually involves antifungal medicines that can be taken orally or applied topically to the affected area. It is important to follow a healthcare provider's instructions for treatment to prevent the spread of the infection to others and to clear up the infection completely.