Biotechnology

Golden rice is a genetically modified variety of rice developed to address Vitamin A deficiency, a prevalent issue in many parts of the world, especially in regions where rice is a staple food. Let's explore why the correct answer is: It is Vitamin A enriched, with a gene from daffodil.

1. Understanding Golden Rice: Golden rice is rice enriched with beta-carotene, a precursor of Vitamin A. This enhancement is achieved by introducing specific genes into the rice genome.
2. Genetic Modification Process: The significant step in developing Golden Rice was the introduction of a gene from the daffodil (Narcissus pseudonarcissus) which produces phytoene synthase and a gene from a soil bacterium (Erwinia uredovora), which produces another enzyme, carotene desaturase. These enzymes transform geranylgeranyl diphosphate into beta-carotene.
3. Significance of Vitamin A: Vitamin A is crucial for visual health, immune function, and cell growth. Deficiencies can lead to severe health problems, including blindness and increased mortality in children.
4. Evaluation of Other Options:
   • Option 2: "It is pest resistant, with a gene from Bacillus thuringiensis." - This description is typical for Bt crops, like Bt cotton, where genes from Bacillus thuringiensis provide pest resistance but not applicable to Golden rice, which is not genetically modified for pest resistance.
   • Option 3: "It is drought tolerant, developed using Agrobacterium vector." - While many plants are modified using Agrobacterium, the primary goal for Golden Rice is not drought tolerance.
   • Option 4: "It has yellow grains, because of a gene introduced from a primitive variety of rice." - The yellow color of the grains is indeed due to beta-carotene, but not from primitive varieties of rice. It's due to genetic modification with genes from daffodil and bacterium.
5. Conclusion: Given this information, the correct statement about Golden Rice is that it is Vitamin A enriched, with a gene from daffodil (Option 1). This trait is specifically designed to help alleviate Vitamin A deficiency-related health issues in rice-dependent regions.

To determine the correct options regarding insulin, let's evaluate each statement individually:

1. (a) C-peptide is not present in mature insulin.
   Mature insulin does indeed not contain the C-peptide. During insulin maturation, the C-peptide is removed from pro-insulin to form the active insulin hormone consisting of A and B chains. Thus, this statement is correct.
2. (b) The insulin produced by rDNA technology has C-peptide.
   This statement is incorrect. rDNA technology is typically used to produce human insulin in its mature form, without C-peptide, similar to naturally occurring insulin. The purpose of recombinant human insulin is to replicate the function of naturally occurring insulin, which does not have the C-peptide.
3. (c) The pro-insulin has C-peptide.
   Pro-insulin is the precursor to insulin and contains the C-peptide linking the A and B chains. During the conversion to active insulin, the C-peptide is cleaved off. Therefore, this statement is correct.
4. (d) A-peptide and B-peptide of insulin are interconnected by disulphide bridges.
   This statement is correct. In the structure of mature insulin, A and B chains are interconnected by disulfide bridges, which are crucial for the molecule's stability and function.

After evaluating each statement, the correct options are (a), (c), and (d). Therefore, the correct answer is:

(a), (c) and (d) only

To solve the question of matching List - I with List - II correctly, we need to understand the biological terms mentioned and find their corresponding matches.

1. Lenticels: These are small openings found in the bark of woody plants that allow for the exchange of gases. Thus, lenticels correspond to (iii) Exchange of gases.
2. Cork cambium: This is a type of secondary meristem in plants that forms periderm (cork). The cork cambium is also known as phellogen. Therefore, cork cambium matches (i) Phellogen.
3. Exchange of gases: This is associated with the function provided by lenticels. However, in this context, it refers to the correct insertion in the sequence, confirming our previous point that lenticels are related to gas exchange.
4. Cork: This refers to the protective outer layer of the bark, which also involves suberin deposition to reduce water loss. Hence, cork matches (ii) Suberin deposition.

Based on the above explanations, the correct matching is:

• (a) Lenticels - (iii) Exchange of gases
• (b) Cork cambium - (i) Phellogen
• (c) Exchange of gases - Not needed separately as it corroborates point (a)
• (d) Cork - (ii) Suberin deposition

The correct answer that matches these associations is (iii) (i) (iv) (ii).

Let's verify the rest of the options:

• Option (iv) (ii) (i) (iii): This does not correspond to the correct pairings as identified.
• Option (iv) (i) (iii) (ii): This is not a correct sequence as established from our explanations.
• Option (ii) (iii) (iv) (i): These pairings are incorrect as per the logical matches discussed.

Therefore, the correct option is indeed (iii) (i) (iv) (ii).

The question asks about the appearance of DNA strands on a gel that has been stained with ethidium bromide, when viewed under UV radiation. Let's break this down step-by-step:

1. Understanding Ethidium Bromide: Ethidium bromide (EtBr) is a commonly used fluorescent dye in molecular biology. It intercalates between the base pairs of DNA.
2. UV Radiation Activation: When exposed to ultraviolet (UV) light, ethidium bromide emits fluorescence. This property is utilized in gel electrophoresis to visualize DNA.
3. Emitted Color Observation: When excited with UV light, ethidium bromide emits a bright orange fluorescence. This is due to its specific fluorescent emission spectrum.

Therefore, when you look at a DNA gel stained with ethidium bromide under UV light, the DNA bands appear as bright orange bands. This distinctive orange color helps researchers to see the location and size of the DNA fragments after electrophoresis.

Justification of Options:

• Bright blue bands: This would typically be seen with other dyes or staining methods, but not with ethidium bromide under UV light.
• Yellow bands: This is not the color emitted by ethidium bromide under UV light.
• Bright orange bands: Correct, as explained above. This is the characteristic fluorescence observed with ethidium bromide.
• Dark red bands: This is not observed in this context and does not refer to the emission of ethidium bromide under UV light.

In conclusion, upon viewing DNA gel stained with ethidium bromide under UV light, the DNA strands appear as bright orange bands, making option "Bright orange bands" the correct answer.

The question pertains to the genetic engineering concept involving plasmid vectors and restriction enzymes. Let's understand the situation:

1. Plasmid pBR322 is commonly used as a cloning vector in molecular biology. It carries two sets of antibiotic resistance genes: one for ampicillin (amp^R) and the other for tetracycline (tet^R).
2. The PstI restriction enzyme cuts the plasmid at a specific site within the amp^R gene.
3. In this scenario, PstI is used to insert a foreign gene (in this case, the gene for β-galactoside production) into the plasmid. The insertion disrupts the amp^R gene because it occurs at its locus.
4. With the amp^R gene disrupted, the resulting recombinant plasmid will no longer confer resistance to ampicillin. This means that cells transformed with this plasmid will not survive on a medium containing ampicillin.
5. However, they will potentially express the β-galactoside gene, assuming the gene is inserted in the correct orientation and under appropriate regulatory controls.

Let's evaluate the options:

• Option 1: "It will be able to produce a novel protein with dual ability." This is incorrect because while the β-galactoside protein may be produced, the plasmid will lose the ability to confer ampicillin resistance due to the disruption of the amp^R gene.
• Option 2: "It will not be able to confer ampicillin resistance to the host cell." This is correct as the insertion of the gene within the amp^R site disrupts ampicillin resistance.
• Option 3: "The transformed cells will have the ability to resist ampicillin as well as produce β-galactoside." This is incorrect since the ampicillin resistance is lost.
• Option 4: "It will lead to lysis of host cell." This is incorrect because the process described does not necessarily cause cell lysis.

Based on the explanation, the correct answer is: it will not be able to confer ampicillin resistance to the host cell.

The question asks about the detection of a mutated gene causing cancer by using a radioactive probe in molecular biology experiments. Let's explore why the correct answer is: "mutated gene does not appear on a photographic film as the probe has no complementarity with it."

1. Understanding the Concept: In molecular genetics, radioactive probes are used to detect specific DNA sequences. These probes are labeled with a radioactive isotope and can hybridize (bind) to complementary DNA sequences.
2. Mechanism of Detection: When a probe hybridizes with its target DNA, it forms a double-stranded structure. This hybridization can be detected via autoradiography, where a photographic film is exposed to the radioactive signal, showing a dark band where hybridization occurs.
3. Effect of Mutation: A mutated gene often means that the sequence of bases in DNA is changed. If these changes affect the sequence complementary to the probe, hybridization might not occur.
4. Correct Option Analysis: When the probe has no complementarity with the mutated gene due to changes in the sequence, no hybridization occurs. Consequently, there is no radioactive signal to appear on the photographic film.
5. Incorrect Option Analysis:
   • "Mutated gene does not appear on photographic film as the probe has complementarity with it." - Contradictory, because if there were complementarity, a signal would appear.
   • "Mutated gene completely and clearly appears on a photographic film." - Incorrect. This option does not consider the lack of complementarity.
6. Conclusion: The mutated gene does not show up on the photographic film because the probe lacks complementarity with the altered DNA sequence.

To determine which stage of meiosis involves the division of the centromere, we need to understand what occurs during each stage of meiosis.

1. Metaphase I: During this stage, homologous chromosomes line up along the equatorial plane of the cell. Importantly, the centromeres do not divide in Metaphase I as this stage is part of Meiosis I, where homologous chromosomes are separated, not the sister chromatids.
2. Metaphase II: In this stage of Meiosis II, chromosomes line up at the equator as they did in Metaphase I. However, the centromeres remain intact and do not yet divide.
3. Anaphase II: This is the stage where the centromeres finally divide, allowing sister chromatids to be pulled apart to opposite poles of the cell. This is a crucial step for separating the sister chromatids and therefore involves the division of the centromere.
4. Telophase II: In this final stage, the separated chromatids reach the opposite poles, and nuclei reform, but by this point, the centromeres have already divided, and their division is not what characterizes this stage.

Therefore, the correct answer is Anaphase II, as this is the stage where the centromere division occurs, allowing for the separation of sister chromatids.

Polymerase Chain Reaction (PCR) is a widely used technique in molecular biology to amplify DNA sequences. This process involves three main steps: Denaturation, Annealing, and Extension. Below is the correct sequence of steps involved in PCR along with explanations:

1. Denaturation: In the first step, the double-stranded DNA is heated to a high temperature of about 94-98°C. This high heat causes the hydrogen bonds between the DNA strands to break, resulting in the separation of the double helix into two individual strands. This separation is necessary for the primers to bind to the DNA strands in the next step.
2. Annealing: After denaturation, the temperature is lowered to about 50-65°C. During this step, short DNA sequences known as primers, which are complementary to the target DNA region, bind (or anneal) to their specific sites on the separated DNA strands. Annealing temperature is crucial as it ensures the specificity of primers binding to the template DNA.
3. Extension: In this step, the temperature is adjusted to approximately 72°C, which is optimal for the DNA polymerase enzyme to work. The enzyme extends the primers by adding nucleotides to the 3’ ends of each primer, effectively synthesizing new strands of DNA complementary to the original template strands.

Hence, the correct sequence that represents the steps of a PCR cycle is: Denaturation, Annealing, Extension. This sequence helps to exponentially amplify the desired DNA fragments.

In recombinant DNA technology, the purification of nucleic acids is a crucial step. One common method used to precipitate nucleic acids is the addition of chilled ethanol.

Here's how the process works:

1. Nucleic acids such as DNA and RNA are often soluble in aqueous solutions. This solubility is due to their hydrophilic nature.
2. To precipitate these nucleic acids, solvents like ethanol or isopropanol are used. When cold ethanol is added to an aqueous solution containing DNA, it reduces the solubility of the DNA.
3. Chilled ethanol reduces the dielectric constant of the solution, causing the negatively charged DNA molecules to aggregate and precipitate out of the solution.

Let's consider the given options:

• Polysaccharides: While polysaccharides can also be precipitated in alcohol, the efficiency is typically lower compared to nucleic acids.
• RNA: RNA can also be precipitated using ethanol; however, in this context, the focus is primarily on DNA precipitation during recombinant DNA purification processes.
• DNA: This is indeed the target molecule for precipitation during the purification process in recombinant DNA technology. Chilled ethanol effectively precipitates DNA, making it the correct answer.
• Histones: These are proteins, and they do not precipitate with ethanol as nucleic acids do.

Conclusion: The addition of chilled ethanol in the purification process for recombinant DNA technology specifically precipitates out DNA, making it the correct answer.

In nature, competing species have evolved various mechanisms that allow them to coexist despite the presence of interspecific competition. Understanding these mechanisms is crucial in the study of ecology and species interactions.

Let's examine the options provided:

1. Predation: This is a biological interaction where one organism (the predator) kills and eats another organism (the prey). While predation affects species interactions, it is not directly a mechanism for competing species to survive together.
2. Resource Partitioning: This is a strategy that allows competing species to coexist by utilizing different resources or the same resources in different ways or at different times. For instance, two different species of birds might feed on insects from different parts of a tree. By reducing direct competition through specialization, resource partitioning enhances survival.
3. Competitive Release: This occurs when a species expands its ecological niche in the absence of competition. This isn't a mechanism by which species actively evolve to coexist; rather, it occurs when competition is reduced or absent.
4. Mutualism: This is a type of symbiotic relationship where both species benefit. While mutualism can influence species interactions, it isn't specifically a mechanism evolved to manage competition for the same resources.

After analyzing the options, resource partitioning emerges as the correct answer. The concept of resource partitioning helps to reduce direct competition and allows species to coexist by sharing different niches within the same environment.

In summary, many species coexist through resource partitioning, which allows them to minimize competition for resources by adapting to use different portions or characteristics of the habitat or resource base. This adaptation is crucial in maintaining biodiversity.