General Questions in English

(A) $Viricide$ is a substance or agent that can deactivate or destroy viruses.
Unlike bacteria,viruses are not living cells,so they are not 'killed' in the traditional sense; instead,they are inactivated by disrupting their structure (such as the protein coat or envelope) or by interfering with their ability to replicate.
Therefore,the correct term for a substance that inactivates a virus is $Viricide$.

(A) Interferons were discovered in $1957$ by Alick Isaacs and Jean Lindemann. They are a group of signaling proteins made and released by host cells in response to the presence of several viruses.

(B) The oral polio vaccine $(OPV)$,also known as the Sabin vaccine,was developed by Albert Sabin in $1961$.
It contains an attenuated (weakened) form of the poliovirus.
In contrast,Jonas Salk developed the first successful inactivated polio vaccine $(IPV)$ in $1955$.
Therefore,the development of polio vaccines is primarily associated with Salk and Sabin.

(A) Surgical instruments are boiled in water to achieve sterilization. Boiling at $100^{\circ}C$ effectively kills most pathogenic microorganisms,including bacteria and viruses,thereby preventing the transmission of infections during surgical procedures.

(D) vector is an organism,typically an arthropod (like a mosquito,tick,or flea),that does not cause the disease itself but acts as a carrier to transmit infectious pathogens from one host to another.
For example,the female Anopheles mosquito acts as a vector for the Plasmodium parasite,which causes malaria.

(D) $Joseph Lister$ was a British surgeon who pioneered the use of carbolic acid (phenol) to sterilize surgical instruments and clean wounds.
His work significantly reduced post-operative infections and mortality rates.
Due to these revolutionary contributions to medical hygiene,he is widely recognized as 'The Father of Modern Antiseptic Surgery'.

(C) An $Antibiotic$ is a chemical substance produced by microorganisms (such as bacteria or fungi) that,in low concentrations,inhibits the growth of or kills other microorganisms.
$Antiseptics$ are chemicals applied to living tissues to reduce the possibility of infection.
$Anticoagulants$ are substances that prevent blood clotting.
$Anti-allergic$ drugs are used to treat allergic reactions.
Therefore,the correct term for a compound produced by an organism that inhibits the growth of other organisms is an $Antibiotic$.

(D) An $Antibiotic$ is a chemical substance produced by microorganisms (such as bacteria or fungi) that, in low concentrations, inhibits the growth of or kills other microorganisms (parasitic organisms).
$Exotoxin$ is a toxin secreted by bacteria.
$Bactericide$ is a substance that kills bacteria, which can be chemical or biological.
$Antibody$ is a protein produced by the immune system of an organism to neutralize pathogens.
Therefore, the correct term for a chemotherapeutic substance derived from a living organism with an inhibitory effect on parasites is an $Antibiotic$.

(C) $Bacterin$ is a suspension of killed or attenuated (weakened) bacteria that is used for artificial immunization.
It stimulates the immune system to produce antibodies against the specific pathogen without causing the disease.
$Bacteriocin$ refers to proteinaceous toxins produced by bacteria to inhibit the growth of similar bacterial strains.
$Bacteriolysin$ is an antibody or substance that causes the dissolution (lysis) of bacteria.
$Barophile$ refers to organisms that thrive at high atmospheric pressure.

(D) $Bacteriolysin$ is a specific substance,such as an antibody or a protein,that causes the disintegration or lysis of bacterial cells.
$Bacteriocin$ refers to proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strains.
$Bacterin$ is a suspension of killed or attenuated bacteria used as a vaccine.
$Barophile$ refers to organisms that thrive at high atmospheric pressures.
Therefore,the correct term for a substance that causes bacterial lysis is $Bacteriolysin$.

(B) The germ theory of disease was proposed by Louis Pasteur. Based on his extensive research on fermentation and the study of microorganisms,he concluded that many diseases are caused by the presence and actions of specific microorganisms. This theory revolutionized medical science and was quickly recognized by the scientific community.

(D) $DPT$ stands for Diphtheria,Pertussis (whooping cough),and Tetanus vaccine.
It is a combination vaccine used to protect against these three infectious diseases.
Diphtheria is caused by the bacterium $Corynebacterium$ $diphtheriae$.
Pertussis (whooping cough) is caused by the bacterium $Bordetella$ $pertussis$.
Tetanus is caused by the bacterium $Clostridium$ $tetani$.

(A) Bacteria produce various poisonous substances that are generally referred to as toxins.
These are broadly classified into two types:
$1$. Exotoxins: These are proteins secreted by living bacterial cells into the surrounding medium.
$2$. Endotoxins: These are components of the bacterial cell wall (specifically lipopolysaccharides in Gram-negative bacteria) that are released upon the death and lysis of the bacterial cell.
Therefore,the correct term for these poisonous substances is toxins.

(C) $Pseudomonas$ species are known to cause spoilage of food products. The consumption of such contaminated food can lead to gastrointestinal distress,specifically stomach pain.

(C) When kerosene,paraffin,or petroleum oil is sprinkled over a pond,it forms a thin film on the water surface.
This film prevents the mosquito larvae and pupae from accessing atmospheric oxygen through their respiratory siphons.
As a result,the larvae and pupae die due to a lack of oxygen,a condition known as asphyxiation.

(D) The Bengal famine of $1943$ was primarily caused by the brown leaf spot disease of rice.
This disease is caused by the fungus $Helminthosporium$ $oryzae$ (also known as $Cochliobolus$ $miyabeanus$).
It led to a massive reduction in rice yield,resulting in a severe food shortage in the Bengal region.
Therefore,the correct option is $D$.

(C) $Aspergillus$ $flavus$ grows on stored cereal grains,groundnut,and areca nut,and produces a carcinogenic toxin called aflatoxin. Therefore,$Aspergillus$ is the correct answer.

(D) The correct answer is $D$. An $Epiphytotic$ disease is a widespread plant disease that occurs in a virulent state,similar to an epidemic in humans.
Examples include $Late$ $blight$ $of$ $potato$,$rust$ $of$ $wheat$,$red$ $rot$ $of$ $sugarcane$,and various $downy$ and $powdery$ $mildews$.
The pathogen responsible for these diseases is often present in the environment,but the disease manifests widely only when environmental conditions become favorable for a short,periodic duration.

(D) The correct answer is $D$. Bordeaux mixture was the first fungicide to be discovered.
It was discovered by Professor Millardet of Bordeaux University.
This mixture consists of copper sulphate, lime, and water $(calcium\, hydroxide)$.
This mixture is often called the 'holy water of plant pathology' and is effective against white rust, mildews, and blights.

(C) . Sporadic diseases occur occasionally at irregular intervals in limited areas,and only a few plants in a locality are infected. Examples include the Blotch disease of cucumbers and the angular leaf spot of cotton.

(B) Phytoalexins are antimicrobial compounds synthesized de novo by plants that accumulate rapidly at areas of pathogen infection.
They are part of the plant's defense mechanism against various pathogens,including fungi,bacteria,and viruses.
These compounds are not present in the plant before infection but are produced in response to stress or pathogen attack to inhibit the growth of the invading organism.

(C) vector is an organism that transmits a disease or parasite from one animal or plant to another.
$1$. $Anopheles$ is a mosquito that acts as a vector for malaria.
$2$. $Musca$ (housefly) acts as a mechanical vector for various diseases like cholera and typhoid.
$3$. $Culex$ is a mosquito that acts as a vector for filariasis and Japanese encephalitis.
Therefore,the set containing $Anopheles$,$Musca$,and $Culex$ consists entirely of vectors.

(A) The $Anopheles$ mosquito is characterized by its resting posture,where it sits at an acute angle to the surface on which it rests.
In contrast,other common mosquitoes like $Culex$ and $Aedes$ typically rest in a position parallel to the surface.

(A) The diseases mentioned are transmitted by insects:
$1$. Filaria is transmitted by the $Culex$ mosquito.
$2$. Malaria is transmitted by the $Anopheles$ mosquito.
$3$. Dengue is transmitted by the $Aedes$ mosquito.
$4$. Yellow Fever is transmitted by the $Aedes$ mosquito.
$5$. Sleeping Sickness is transmitted by the Tsetse fly.
Since all these vectors (mosquitoes and flies) belong to the class $Insecta$ of the phylum $Arthropoda$,the correct answer is Insects.

(C) The housefly,belonging to the genus $Musca$,is considered the greatest mechanical carrier of diseases.
It carries pathogens on its legs,wings,and body parts from contaminated surfaces like garbage and excreta to human food.
Because of its habit of visiting both filth and food,it acts as a primary vector for diseases such as cholera,typhoid,and dysentery.

(C) Lysozymes are antibacterial enzymes that act as a chemical barrier in the innate immune system.
They are present in various body secretions,including saliva and tears,where they help in breaking down the cell walls of bacteria to prevent infections.

(D) The ability of a nation to produce athletes capable of competing at the Olympic level is primarily determined by the overall health of its population.
Good health is the foundation of physical fitness,endurance,and performance.
While diet,body size,and longevity are factors,they are all components that contribute to the broader concept of health.
Therefore,health is the most comprehensive and critical factor for athletic success.

(C) Megaloblastic anaemia is a condition characterized by the presence of abnormally large,immature red blood cells (megaloblasts) in the bone marrow.
During pregnancy,the demand for folate (Vitamin $B_9$) increases significantly to support the rapid growth and development of the fetus.
$A$ deficiency in folic acid is the most common cause of megaloblastic anaemia during pregnancy.
While Vitamin $B_{12}$ deficiency can also cause megaloblastic anaemia,folic acid deficiency is specifically and most frequently associated with the increased physiological requirements of pregnancy.

(D) Beri-beri is a disease caused by a deficiency of Vitamin $B_1$ (Thiamine).
It primarily affects the peripheral nervous system,leading to symptoms like muscle weakness and nerve damage (polyneuritis).
It also significantly impacts the gastro-intestinal tract,causing loss of appetite and indigestion.
Furthermore,it affects the cardiovascular system,which can lead to heart failure in severe cases (wet beri-beri).

(B) The spleen is a large,bean-shaped organ which primarily acts as a filter for the blood.
It contains lymphocytes and phagocytes,which help in destroying pathogens.
Therefore,the spleen is classified as a secondary lymphoid organ in the human body.

(C) Blood transfusion is a critical medical procedure. To ensure the safety of the recipient,the stored blood must be screened and free from any infectious biotic potentialities,which include viruses (like $HIV$,$Hepatitis$),bacteria,parasites,and other pathogens that could cause disease transmission.

(A) . Streptomycin and related antibiotics bind to the $30S$ small subunit of prokaryotic ribosomes.
This binding interferes with the initiation of protein synthesis and causes misreading of the genetic code,ultimately leading to the inhibition of protein synthesis.
Since eukaryotic ribosomes differ in structure ($80S$ vs $70S$),these antibiotics specifically target bacterial protein synthesis without harming human cells.

(B) Psychiatry is the branch of medicine focused on the diagnosis,treatment,and prevention of mental,emotional,and behavioral disorders.
Neurology deals with disorders of the nervous system.
Psychology is the scientific study of the mind and behavior,which does not primarily involve medical treatment of disorders.
Neuropsychiatry is a branch of medicine that deals with mental disorders attributable to diseases of the nervous system.

(D) Robert Koch is credited with establishing the germ theory of disease and identifying specific pathogens for diseases like anthrax,cholera,and tuberculosis. He formulated 'Koch's Postulates',which are a set of criteria used to establish a causative relationship between a microbe and a disease.

(A) The period between the entry of a pathogen into the host body and the appearance of the first clinical symptoms of the disease is defined as the $Incubation \text{ } period$. During this time, the pathogen multiplies within the host to reach a threshold level required to trigger an immune response or cause tissue damage, leading to symptoms.

(B) Pathogens are biological agents that cause disease in their hosts.
In the context of immunology,pathogens often possess molecules on their surface known as antigens,which are recognized by the immune system as foreign.
While pathogens are the disease-causing organisms,they are frequently referred to as antigens because they trigger an immune response.

(B) The concept of 'vaccination' was pioneered by $Edward \ Jenner$ in $1796$.
He observed that milkmaids who had contracted cowpox were immune to smallpox.
He successfully tested this by inoculating a young boy with cowpox material,which provided immunity against the deadly smallpox virus.
Therefore,$Edward \ Jenner$ is known as the father of immunology.

(D) The correct answer is $D$.
Lymphocytes are a type of white blood cell involved in the immune response.
Histamine is a chemical mediator released primarily by mast cells and basophils, not lymphocytes, which causes vasodilation (dilation of blood vessels) and increases capillary permeability during inflammatory responses.
Pyrogens are substances that induce fever.
Interferons are proteins secreted by virus-infected cells to protect non-infected cells.
Since none of the options correctly identify a protein secreted by lymphocytes that causes vasodilation, the correct choice is $None \text{ of the above}$.

(C) The triple antigen vaccine,commonly known as the $DPT$ vaccine,protects against Diphtheria,Pertussis (whooping cough),and Tetanus.
According to the standard immunization schedule (such as the National Immunization Schedule in India),the first dose of the $DPT$ vaccine is administered to an infant at the age of $6$ weeks.
Among the given options,the most appropriate timing for the initiation of the primary vaccination series is at $6$ weeks,which is approximately $1.5$ months. However,in many simplified contexts,it is associated with the early vaccination schedule starting around the $6$th week.

(C) Vaccines are biological preparations that provide active acquired immunity to a particular infectious disease. They are often prepared from weakened or killed forms of the microbe,its toxins,or one of its surface proteins. In the context of passive immunity,antisera (serum containing antibodies) are used. However,the term 'vaccine' is most commonly associated with preparations that stimulate the immune system to produce antibodies. Among the given options,the concept of immunization is most closely related to the use of serum (containing antibodies) for passive immunity or the preparation of vaccines that trigger an immune response.

(D) The $DPT$ vaccine is a combination vaccine used to protect against three infectious diseases:
$1$. $D$ stands for Diphtheria,a bacterial infection affecting the mucous membranes of the throat and nose.
$2$. $P$ stands for Pertussis (also known as whooping cough),a highly contagious respiratory tract infection.
$3$. $T$ stands for Tetanus,a serious bacterial infection that causes painful muscle spasms and can lead to death.
Therefore,the correct option is $D$.

(A) When the body is infected by pathogens,$WBC$s (specifically macrophages) release chemical substances known as pyrogens.
These pyrogens act on the hypothalamus in the brain to increase the body's set-point temperature,resulting in a fever.
Fever is a defense mechanism that helps the body fight off infections by creating an unfavorable environment for the growth of many pathogens.

(A) The triple antigen vaccine,known as $DPT$,protects against Diphtheria,Pertussis (whooping cough),and Tetanus.
According to the National Immunization Schedule $(NIS)$,the primary doses are given at $6, 10,$ and $14$ weeks.
The first booster dose of $DPT$ is recommended for children between $16-24$ months of age,which is approximately $1.5$ to $2$ years old. Among the given options,the most appropriate timeframe for the booster dose is $18-24$ months.

(C) Antiseptics are chemical substances that prevent the growth of microorganisms or kill them and are safe to be applied on living tissues.
Carbolic acid (phenol) in a dilute solution (usually $0.2\%$ to $1\%$) acts as an antiseptic.
Bordeaux mixture is a fungicide,$DDT$ is an insecticide,and Hydrocyanic acid gas is a highly toxic fumigant.

(B) The inactivated polio vaccine $(IPV)$,also known as the Salk vaccine,was developed by $Dr. Jonas Salk$ in $1955$.
It consists of inactivated (killed) poliovirus strains of all three poliovirus types.
This vaccine is administered by injection and provides immunity against poliomyelitis.

(B) The house fly ($Musca$ $domestica$) acts as a mechanical vector for several diseases like typhoid,cholera,and dysentery by carrying pathogens on its body from contaminated surfaces to food.
Yellow fever is a viral disease caused by the yellow fever virus.
It is transmitted to humans primarily through the bite of infected mosquitoes,specifically those belonging to the $Aedes$ and $Haemagogus$ genera (formerly classified under $Stegomyia$).
Therefore,yellow fever is not transmitted by house flies.

(B) Biological agents of disease are living organisms that can cause infections or diseases in a host.
These include pathogens such as $Viruses$,$Bacteria$,$Fungi$,$Protozoa$,and $Helminths$ (worms).
Option $A$ refers to nutritional factors,while option $C$ refers to physical agents of disease.
Therefore,option $B$ is the correct answer.

(B) Interferons are a group of signaling proteins made and released by host cells in response to the presence of several viruses.
They are antiviral proteins that prevent further viral replication in neighboring uninfected cells.
When a cell is infected by a virus,it secretes interferons,which signal nearby cells to heighten their antiviral defenses.
Therefore,the correct answer is $B$ (Interferon).

(B) The Pulse-Polio programme is a massive public health campaign initiated by the Government of India.
Its primary objective is to achieve the complete eradication of the polio virus from the country through widespread vaccination.
By providing oral polio vaccine $(OPV)$ to children,the programme aims to break the chain of transmission and ensure that no new cases of polio occur.
Therefore,the correct purpose is to eradicate polio.

(D) The housefly $(Musca \text{ domestica})$ acts as a mechanical vector for several pathogens, including those causing $Leprosy$, $Dysentery$, and $Typhoid$. However, $Sleeping \text{ sickness}$ (African trypanosomiasis) is caused by the protozoan $Trypanosoma \text{ brucei}$ and is transmitted by the $Tse-tse \text{ fly}$ $(Glossina \text{ species})$, not the housefly. Therefore, the correct option is $D$.