Multiple Choice Question Of Biology - NEET MCQ

Lymphokines are cytokines produced by T cells (lymphocytes) of the immune system. Lymphokines act to attract additional immune cells to mount an immune response, for instance in stimulating B cells to generate antibodies against the invading pathogen.

Explanation:
The substance present in certain individuals that stimulates the production of antibodies in other members of the same species but not in the donor is called an alloantigen.
- Alloantigen: It is a type of antigen that is present in some individuals of a species but not in all individuals. When an individual is exposed to an alloantigen, it stimulates the production of antibodies in other members of the same species, but not in the donor.
- Isoantigen: Isoantigen refers to an antigen that is present in different individuals of the same species. It can stimulate the production of antibodies in both the donor and other members of the species.
- Answer: The correct answer is C: Both. The substance described in the question is an alloantigen, which means it can stimulate the production of antibodies in other members of the same species but not in the donor.

Explanation:
The human blood groups A, B, AB, and O are an example of multiple allelism. Multiple allelism refers to the existence of more than two alleles of a gene in a population. In the case of the ABO blood group system, there are three alleles involved: A, B, and O.
Key Points:
- The ABO blood group system is determined by the presence or absence of antigens (A and B) on the surface of red blood cells.
- The A allele codes for the A antigen, the B allele codes for the B antigen, and the O allele codes for neither antigen.
- An individual can inherit two alleles for the ABO blood group, one from each parent.
- The possible combinations of alleles are: AA, AO, BB, BO, AB, and OO.
- The A and B alleles are codominant, meaning that both antigens can be present if an individual has the AB genotype.
- The O allele is recessive to both A and B, so individuals with the OO genotype do not have either antigen.
Therefore, the ABO blood group system demonstrates multiple allelism, as there are more than two alleles (A, B, and O) of the gene responsible for determining blood type.

The humoral immune system defends mostly against bacteria and viruses in the body fluids.
The humoral immune system is a component of the adaptive immune system that is responsible for producing antibodies and other immune proteins called immunoglobulins. These antibodies neutralize pathogens such as bacteria and viruses, preventing them from causing harm to the body.
Here is a detailed explanation of the answer:
1. Definition of the humoral immune system:
- The humoral immune system is a branch of the adaptive immune system, which defends the body against pathogens by producing antibodies.
- Antibodies are proteins that recognize and bind to specific foreign substances, such as bacteria and viruses.
2. Function of the humoral immune system:
- The primary function of the humoral immune system is to defend against bacteria and viruses.
- Antibodies produced by B cells in response to an infection or vaccination can neutralize these pathogens, preventing their spread and infection of host cells.
3. Target of the humoral immune system:
- The humoral immune system primarily targets pathogens present in body fluids, such as blood, lymph, and mucus secretions.
- Bacteria and viruses that enter the body through various routes, including respiratory, digestive, or urogenital tracts, can be targeted by antibodies.
4. Role of antibodies in defense:
- Antibodies bind to specific antigens on the surface of bacteria or viruses, marking them for destruction by other components of the immune system.
- Antibodies can neutralize pathogens by preventing them from attaching to host cells or by enhancing phagocytosis, a process where immune cells engulf and destroy the pathogens.
5. Examples of pathogens targeted by the humoral immune system:
- Common bacterial infections, such as pneumonia, urinary tract infections, and sepsis, are defended against by the humoral immune system.
- Viral infections, including influenza, measles, and hepatitis, are also targeted by the humoral immune system.
In conclusion, the humoral immune system defends mostly against bacteria and viruses in body fluids. Antibodies produced by the humoral immune system neutralize these pathogens and prevent their spread in the body.

Protein targeting pathways
- Proteins need to be sorted and transported to their proper cellular localization to perform their specific functions within the cell.
- Protein targeting pathways are the processes that ensure proteins are correctly delivered to their intended destinations.
- These pathways involve a series of steps, including protein synthesis, protein folding, and protein transport.
- There are different protein targeting pathways depending on the destination of the protein, such as the endoplasmic reticulum (ER), Golgi apparatus, mitochondria, nucleus, or plasma membrane.
- The protein targeting pathways can be classified into two main types: post-translational and co-translational targeting.
- In post-translational targeting, proteins are synthesized in the cytosol and then transported to their destination organelles.
- In co-translational targeting, proteins are targeted to the ER while they are still being synthesized by ribosomes.
- The protein targeting pathways involve various molecular mechanisms, including signal sequences, targeting factors, and membrane translocation complexes.
- Protein targeting pathways play a crucial role in maintaining cellular organization and function.

Ribosomes consist of protein and RNA
Ribosomes are particles that play a crucial role in protein synthesis. They consist of both protein and RNA molecules.
Ribosomes are about 200 Å units in diameter
The diameter of ribosomes is approximately 200 Å (angstroms).
Percentage of protein in ribosomes
The percentage of protein in ribosomes is:
- 40%
Percentage of RNA in ribosomes
The percentage of RNA in ribosomes is:
- 60%
Conclusion
- The correct answer is B: 40% protein and 60% RNA.

What happens to all the energy passed from one element to the next in a food chain?
The energy passed from one element to the next in a food chain undergoes several processes and ultimately dissipates into the environment. Here is a detailed explanation of what happens to the energy:
1. Energy transfer through trophic levels:
- Producers (plants) capture energy from the sun through photosynthesis and convert it into chemical energy.
- Herbivores (primary consumers) consume the producers and obtain the stored energy.
- Carnivores (secondary and tertiary consumers) consume herbivores and other carnivores, transferring the energy up the food chain.
2. Energy loss at each trophic level:
- As energy moves up the food chain, there is a loss of energy at each trophic level due to metabolic processes and heat loss through respiration.
- Only a fraction of the energy consumed by an organism is assimilated and converted into biomass.
3. Energy dissipation:
- The energy that is not used by organisms for growth, reproduction, or other metabolic activities is dissipated into the environment as heat.
- This dissipation occurs through processes such as respiration, excretion, and movement.
4. Decomposition and nutrient recycling:
- After the death of organisms, decomposers (bacteria, fungi, etc.) break down the organic matter and release the stored energy.
- This energy is eventually recycled back to the producers through nutrient cycling, allowing the energy flow to continue in the ecosystem.
5. Entropy and the second law of thermodynamics:
- The dissipation of energy into the environment is governed by the second law of thermodynamics, which states that energy tends to disperse and become less organized over time. This is known as entropy.
- The continuous dissipation of energy into the environment is necessary to maintain the flow of energy in the ecosystem and support life.
Therefore, the correct answer is D: It is dissipated into the environment.

Characteristics of Genetic Code:
The genetic code is a set of rules that determines how the nucleotide sequence of a gene is translated into the amino acid sequence of a protein. One of the characteristics of the genetic code is that it is non-overlapping, meaning that each codon is read separately and does not overlap with the next codon.
Explanation:
- A base in a mRNA is not used for different codons: This statement is correct. In the non-overlapping genetic code, each nucleotide base in the mRNA is part of only one codon. There is no overlap or sharing of bases between adjacent codons.
- No codon is reserved for punctuation: This statement is not related to the non-overlapping nature of the genetic code. Codons are specific sequences of three nucleotides that code for amino acids, and there are no codons reserved for punctuation in the genetic code.
- A particular codon will always code for the same amino acid: This statement is not directly related to the non-overlapping nature of the genetic code. However, it is true that each codon codes for a specific amino acid, and this relationship is consistent throughout the genetic code.
- The codon has polarity: This statement is not related to the non-overlapping nature of the genetic code. Polarity refers to the directionality or orientation of a molecule, and it is not a characteristic of the genetic code.
Therefore, the correct answer is A: A base in a mRNA is not used for different codons. In the non-overlapping genetic code, each base in the mRNA is part of only one codon, ensuring that there is no ambiguity in the translation process.

The correct answer is D: Hardy-Weinberg law.
The Hardy-Weinberg law, also known as the Hardy-Weinberg equilibrium, states that both gene frequencies and genotype frequencies will remain constant from generation to generation in an infinitely large interbreeding population in which mating is at random and no selection, migration, or mutations occur.
Explanation:
The Hardy-Weinberg law is a fundamental principle in population genetics. It describes the genetic equilibrium that occurs in an idealized population under certain conditions. Here is a detailed explanation of the key concepts related to the Hardy-Weinberg law:
1. Gene frequencies: The law refers to the frequencies of different alleles (alternative forms of a gene) in a population. It states that these frequencies will remain constant over time.
2. Genotype frequencies: The law also applies to the frequencies of different genotypes (the combination of alleles in an individual) in a population. It states that these frequencies will also remain constant over time.
3. Infinitely large interbreeding population: The law assumes that the population is large enough to prevent random fluctuations in gene and genotype frequencies due to chance events. This means that genetic drift, which is the change in gene frequencies due to random sampling, is negligible.
4. Random mating: The law assumes that individuals in the population mate randomly, meaning that there is no preference for specific genotypes or phenotypes. This ensures that the frequencies of different genotypes remain constant.
5. No selection, migration, or mutations: The law assumes that there is no natural selection acting on the population, no migration of individuals into or out of the population, and no mutations occurring in the genes. These factors would otherwise cause changes in gene and genotype frequencies.
Overall, the Hardy-Weinberg law provides a baseline against which deviations in gene and genotype frequencies can be measured. If there are deviations from the law, it suggests that one or more of the assumptions are not met and that evolutionary processes are at work in the population.

Thalamus Shape and Ovary Position
The condition described in the question refers to the shape of the thalamus and the position of the ovary in relation to the other floral parts. The different conditions are:
Epigyny:
- Thalamus shape: Flat or disc-shaped
- Ovary position: Superior (above) the attachment point of other floral parts
- Floral parts arrangement: Stamens, petals, and sepals are inserted below the ovary
Perigyny:
- Thalamus shape: Flat or disc-shaped
- Ovary position: Half-inferior (partially above and partially below) the attachment point of other floral parts
- Floral parts arrangement: Stamens, petals, and sepals are inserted below the ovary
Hypogyny:
- Thalamus shape: Conical or dome-shaped
- Ovary position: Inferior (below) the attachment point of other floral parts
- Floral parts arrangement: Stamens, petals, and sepals are separately and successively inserted below the ovary
None:
- This option does not describe any specific condition related to the shape of the thalamus and the position of the ovary.
Therefore, the correct answer is C: Hypogyny