Biology: CUET Mock Test - 6 - CUET MCQ

The correct option is 'A - III, B - I, C - IV, D - II'.

Key Points

• Aspergillus niger is known for producing Citric acid.
  • It is a microorganism that is used in the industrial production of citric acid.
  • This fungus is capable of converting sugars into citric acid through fermentation processes.
• Clostridium butylicum is associated with the production of Butyric acid.
  • This bacterium is used in the fermentation industry to produce butyric acid.
  • Butyric acid is known for its importance in the food and flavoring industries.
• Saccharomyces cerevisiae is a yeast used for producing Ethanol.
  • It is one of the most well-known yeasts, widely used in the baking and brewing industries for its ability to ferment sugars into ethanol and carbon dioxide.
• Acetobacter aceti is known for its role in producing Acetic acid.
  • It is a bacterium that oxidizes ethanol to acetic acid, a process central to vinegar production.

Therefore, the correct pairing is:
A - III: Aspergillus niger - Citric acid
B - I: Clostridium butylicum - Butyric acid
C - IV: Saccharomyces cerevisiae - Ethanol
D - II: Acetobacter aceti - Acetic acid

Key Points

• Chitinase is used for the isolation of genetic material from fungal cells because the cell walls of fungi are primarily composed of chitin, and chitinase helps in breaking down this component.

Additional Information

• Lysozyme is incorrect because it is primarily used to break down the cell walls of bacteria, which are rich in peptidoglycan, not chitin.
• Pepsin is incorrect as it is a digestive enzyme that breaks down proteins in the stomach, not a component of fungal cell walls.
• Cellulase is incorrect because it breaks down cellulose, which is a major component of plant cell walls, not fungal cell walls.

Key Points

• The correct sequence for the Polymerase Chain Reaction (PCR) process is Denaturation of DNA, Annealing of primers, Extension of primers, and finally the Amplified DNA.
• This sequence is represented by option 3: (C), (A), (D), (B).

Additional Information

• Denaturation of DNA: This first step involves heating the reaction mixture to separate the DNA strands, providing single-stranded DNA templates for the next step.
• Annealing of primers: In this step, the temperature is lowered to allow primers to bind (anneal) to their complementary sequences on the single-stranded DNA templates.
• Extension of primers: The temperature is adjusted so that the DNA polymerase can synthesize the new DNA strand by adding dNTPs (deoxyribonucleotide triphosphates) to the annealed primers.
• Amplified DNA: The result of repeating these steps (denaturation, annealing, extension) is an exponential increase in the specific DNA segment being amplified.

• Option 1: The sequence (A), (C), (B), (D) is incorrect because it does not follow the standard PCR steps.
• Option 2: The sequence (D), (A), (C), (B) is incorrect as it starts with the extension step, which cannot occur before the DNA is denatured and primers are annealed.
• Option 4: The sequence (C), (B), (D), (A) incorrectly places the amplified DNA step before the extension step, which is not feasible in the PCR process.

The correct option is 'A - III, B - IV, C - I, D - II'.

Key PointsPlasmid of Salmonella - Construction of 1st recombinant DNA

• Plasmids are small, circular, double-stranded DNA molecules distinct from a cell's chromosomal DNA.
• They naturally occur in bacterial cells, including Salmonella.
• Plasmids are used in biotechnology as vectors to insert foreign DNA into host cells.
• The construction of the first recombinant DNA involved the use of a plasmid to introduce foreign DNA into a host cell, creating a genetically modified organism.

Restriction enzymes - Molecular scissors

• Restriction enzymes are enzymes that cut DNA at specific recognition nucleotide sequences known as restriction sites.
• They are often referred to as "molecular scissors" because they can cut DNA strands at precise locations, allowing for the manipulation of DNA for cloning, analysis, and other genetic engineering purposes.

Ligases - Join foreign DNA to plasmid

• DNA ligases are enzymes that facilitate the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.
• They are crucial in genetic engineering for ligating foreign DNA into plasmid vectors, a process essential in the construction of recombinant DNA molecules.

β-galactosidase - Insertional inactivation

• β-galactosidase is an enzyme involved in the hydrolysis of β-galactosides into monosaccharides.
• Insertional inactivation is a method used in molecular cloning to detect the insertion of a DNA fragment into a plasmid vector.
• When a gene for β-galactosidase in a plasmid is disrupted by the insertion of foreign DNA, the enzyme's activity is lost, indicating successful cloning.

Conclusion:

Therefore, the correct pairing is

• A - III: Plasmid of Salmonella - Construction of 1st recombinant DNA
• B - IV: Restriction enzymes - Molecular scissors
• C - I: Ligases - Join foreign DNA to plasmid
• D - II: β-galactosidase - Insertional inactivation

Key Points

• Transgenic animals are those that have had their genomes altered through genetic engineering techniques. These animals carry genes from other species, which can give them new traits or characteristics.
• The incorrect statement is that transgenic animals are used "To make better quality seeds." This is because transgenic animals are primarily used in medical and scientific research, not in the production of plant seeds.
• Transgenic animals are indeed used "To study disease" by introducing or modifying genes related to specific human diseases, allowing researchers to study the progression and treatment of these diseases in a living organism.
• They are also used "To test vaccine safety" by carrying genes that make them susceptible to diseases for which vaccines are being developed, thus serving as models for testing the efficacy and safety of these vaccines.
• "To test chemical safety" is another correct use of transgenic animals. They can be engineered to be more sensitive to toxic substances, allowing scientists to study the effects of chemicals and drugs on living organisms.

Additional Information

• The use of transgenic animals is a powerful tool in genetics research, allowing scientists to understand gene functions and their effects on health and disease more clearly.
• While transgenic technology has great potential in various fields, it also raises ethical and environmental concerns that need to be carefully considered.

Antibiotics produced by microbes are regarded as one of the most significant discoveries of the twentieth century and have greatly contributed towards the welfare of the human society. Anti is a Greek word that means ‘against’, and bio means ‘life’, together they mean ‘against life’ (in the context of disease-causing organisms); whereas with reference to human beings, they are ‘pro-life’ and not against. Antibiotics are chemical substances, which are produced by some microbes and can kill or retard the growth of other (disease-causing) microbes.

• Sir Alexander Fleming, a Scottish researcher discovered penicillin in 1928.
• Antibiotics like penicillins produced by useful microbes are used to kill disease-causing harmful microbes.
• Antibiotics have played a major role in controlling infectious diseases like diphtheria, whooping cough and pneumonia.
• For more than a hundred years, microbes are being used to treat sewage (waste-water) by the process of activated sludge formation and this helps in recycling of water in nature.

Hence, we conclude that Penicillin was discovered by Alexander Fleming.

Note

• Edward Jenner discovered the Small Pox Vaccine.
• Robert Koch discovered the causative agents of Cholera, Tuberculosis, Anthrax.
• Robert Hooke discovered cell.

The correct answer is Only 2

RNA polymerase is an enzyme responsible for catalyzing the synthesis of RNA from a DNA template during transcription. Transcription involves three main stages: initiation, elongation, and termination.

• Initiation: In this stage, RNA polymerase binds to the promoter region of the DNA, forming a transcription initiation complex. In prokaryotes, this process often involves the transient association of a sigma factor (σ) with the RNA polymerase core enzyme, which helps in recognizing and binding to the promoter sequence.
• Elongation: Once the initiation complex is formed, RNA polymerase begins moving along the DNA template, synthesizing RNA in the 5' to 3' direction. During elongation, RNA polymerase does not require the transient association of initiation or termination factors. It simply catalyzes the addition of ribonucleotides to the growing RNA chain based on the complementary base pairing with the DNA template.
• Termination: In the termination stage, RNA polymerase recognizes specific sequences in the DNA template that signal the end of the gene or transcription unit. In prokaryotes, termination often involves the transient association of a termination factor (ρ) with the RNA polymerase complex, leading to the release of the newly synthesized RNA molecule and dissociation of RNA polymerase from the DNA template.

Conclusion-
RNA polymerase can perform elongation on its own without the need for additional factors such as the initiation factor (σ) or termination factor (ρ).
During elongation, RNA polymerase moves along the DNA template, catalyzing the addition of ribonucleotides to the growing RNA chain based on the complementary base pairing with the DNA template

The correct answer is Option 3.

Key Points

• Pleiotropy is the phenomenon of a single gene influencing two or more distinct phenotypic traits. Hence Statement 1 is correct.
• An example of a Pleiotropy is phenylketonuria which is a genetic disorder caused by the low metabolism of the amino acid phenylalanine in the body cells.
• Phenylketonuria (PKU) is a rare genetic condition that causes an amino acid called phenylalanine to build up in the body.
  • It is caused by a mutation of the gene responsible for the production of an enzyme called phenylalanine hydroxylase. Hence statement 2 is correct.
  • This enzyme breaks down the amino acid phenylalanine that we get from protein digestion.
  • Without this enzyme, levels of the amino acid phenylalanine increase in the blood and damage the nervous system in infants.
  • This disorder may result in several conditions in infants including intellectual disabilities, seizures, heart problems, and developmental delays.

(A) Correct: Penicillin was discovered by Alexander Fleming from the fungus Penicillium.
(B) Correct: Yeast produces ethanol through anaerobic respiration during fermentation.
(C) Correct: Aerobic bacteria in the sewage treatment process break down organic matter.
(D) Correct: Biofertilizers provide nitrogen to plants, enhancing soil fertility.
(E) Correct: The industrial fermentation of ethanol and alcoholic beverages primarily uses yeast (fungi) to produce alcohol.

(A) Correct: Restriction enzymes cut DNA at specific recognition sequences.
(B) Correct: Vectors are needed to carry the recombinant DNA into host cells for cloning.
(C) Correct: Bioreactors are used to grow cells in a controlled environment for large-scale production.
(D) Incorrect: Recombinant DNA technology is not limited to bacterial cells; it is used in plant and animal cells as well.
(E) Incorrect: Insertion of recombinant DNA into a host leads to replication of the DNA, not necessarily its expression, which requires specific conditions.

(A) Correct: Cloning refers to the process of making multiple copies of a specific gene or DNA segment.
(B) Correct: Competent cells are treated with divalent cations to take up recombinant DNA.
(C) Correct: Vectors with a high copy number ensure efficient replication of recombinant DNA.
(D) Correct: Gene therapy uses genetic engineering to treat or cure genetic disorders in humans.
(E) Incorrect: Restriction enzymes are found in bacteria but can cut DNA from various sources.

The main goal of the Human Genome Project was to identify and map all the genes in human DNA, which includes approximately 20,000-25,000 genes.

Over 99% of human DNA is identical across all individuals, with only minor variations contributing to differences such as physical traits and susceptibility to diseases.

The Human Genome Project was completed over a span of 13 years, from 1990 to 2003.

The Human Genome Project enabled the identification of genetic diseases and laid the foundation for personalized medicine, where treatments can be tailored to an individual’s genetic profile.

The Human Genome Project relied on high-speed DNA sequencing and bioinformatics to process the vast amount of genetic data produced, making it possible to map the entire human genome efficiently.

Darwin proposed natural selection as the mechanism for evolution, where individuals with advantageous traits survive and reproduce more successfully.

Darwin studied the finches with different beak shapes on the Galápagos Islands, which helped him understand the concept of natural selection.

In natural selection, individuals with advantageous traits are more likely to survive and reproduce, passing those traits to their offspring.

Over time, natural selection leads to the evolution of species as advantageous traits accumulate in the population.

Darwin believed that all species of life descended from common ancestors, with the process of evolution leading to the diversity of life forms.

The first biotic community to invade a bare land or area is known as the pioneer community. In a xerarch succession, lichens in the temperate region act as pioneering species. Some examples of lichens are Rinodina, Lecanora, Parmelia, etc.

The sequence of successional stages occurring on bare rocks is known as xerarch succession. The mosses are replaced by the herbaceous plants in a xerarch succession. Some examples of xeric grasses are Aristida, Solidage, Poa, etc.

The sequence of successional stages occurring on bare rocks is known as xerarch succession. It occurs in an area where there is less amount of moisture. It is mostly observed in the desert area.

Ecological succession is the gradual change in the species composition of a given area which can be predicted. Biomass is the total organic material required for energy production.

The sequence of successional stages occurring on bare rocks is known as xerarch succession. It mostly starts with the invasion of lichens and ends with the formation of the forest. The pioneering species grow with time leading to a formation of a climax community called a forest.

The first biotic community to invade a bare land or area is known as the pioneer community. These are the organisms of the first seral stage. They further grow and expand to form a climax community.

The sequence of successional stages occurring on bare rocks is known as xerarch succession. In a xerarch succession, the pioneering species lichens release acids to dissolve rocks. This helps in weathering and soil formation.

The sequence of successional stages occurring on bare rocks is known as xerarch succession. The pioneering species lichens are replaced by mosses in a xerosere. Some examples of mosses are Tortula, Grimmima, Polyerichum, etc.

The habitat having too much dryness is known as a xeric habitat. It is deficient in moisture and is characterized by limited water availability. Desert region is an example of a xeric habitat.