Botany: Section – A (Q. No. 101 to 135)
101. Auxin is used by gardeners to prepare weed-free lawns. But no damage is caused to grass as auxin
(1) promote abscission of mature leaves only
(2) does not affect mature monocotyledonous plants
(3) can help in cell division in grasses, to produce growth
(4) promotes apical dominance
The correct answer is: (2) does not affect mature monocotyledonous plants
Auxins, such as 2,4-D (2,4-Dichlorophenoxyacetic acid), are commonly used as selective herbicides. They promote uncontrolled growth in broadleaf (dicot) weeds, leading to their death, while grasses (monocots) remain unaffected due to differences in their auxin metabolism and sensitivity.
102. Lecithin, a small molecular weight organic compound found in living tissues, is an example of
1) phospholipids
2) Glycerides
3) Carbohydrates
4) Amino acids
The correct answer is: (1) Phospholipids
Lecithin is a type of phospholipid that contains a phosphate group and is a key component of cell membranes. It is commonly found in egg yolks, soybeans, and other biological tissues, playing a crucial role in membrane structure and function.
103. Match List I with List II
List I List II
A. Two or more alternative I. Back cross
forms of a gene
B. Cross of F1 progeny with II. Ploidy
homozygous receive parent
C. Cross of F progeny with III. Allele
any of the parents
D. Number of chromosome IV. Test cross
set in plant
Choose the correct answer from the options given below:
(1) A-II, B-I, C-III, D-IV
(2) A-III, B-I, C-I, D-II
(3) A-IV, B-III, C-III, D-IV
(4) A-IV, B-III, C-III, D-IV
The correct answer is:
(2) A-III, B-I, C-IV, D-II
Here’s the correct matching:
A. Two or more alternative forms of a gene → III. Allele
(Alleles are different forms of a gene that occupy the same position on a chromosome.)
B. Cross of F1 progeny with a homozygous recessive parent → IV. Test cross
(A test cross is used to determine the genotype of an organism by crossing it with a homozygous recessive parent.)
C. Cross of F1 progeny with any of the parents → I. Back cross
(A back cross is when an F1 individual is crossed with one of its parental genotypes.)
D. Number of chromosome sets in a plant → II. Ploidy
(Ploidy refers to the number of complete sets of chromosomes in a cell.)
104. Identify the set of correct statements:
A. The flowers of Vallisneria are colourful and produce nectar
B. The flowers of waterlily are not pollinated by water
C. In most of water -pollinated species, the pollen grains are protected from wetting.
D. Pollen grains of some hydrophytes are long and ribbon like
E. In some hydrophytes, the pollen grains are carried passively inside water.
Choose the correct answer from the options given below:
1. A , B, C and D only
2. A, C, D and E only
3. B, C, D and E only
4. C, D and E only
The correct answer is:
3) B, C, D, and E only
Explanation:
A. The flowers of Vallisneria are colourful and produce nectar → ❌ Incorrect
Vallisneria is a water-pollinated (hydrophilous) plant. Its flowers are not colorful and do not produce nectar, as they rely on water for pollination.
B. The flowers of water lily are not pollinated by water → ✅ Correct
Water lily (Nymphaea) is pollinated by insects, not water, even though it grows in aquatic environments.
C. In most water-pollinated species, the pollen grains are protected from wetting → ✅ Correct
Water-pollinated plants have adaptations such as mucilage covering or being lightweight to prevent pollen from sinking or getting wet.
D. Pollen grains of some hydrophytes are long and ribbon-like → ✅ Correct
In hydrophytes like Zostera (seagrass), pollen grains are long and ribbon-like to increase the chances of contact with the stigma.
E. In some hydrophytes, the pollen grains are carried passively inside water → ✅ Correct
In submerged hydrophytes, pollen grains are transported by water currents passively.
Thus, the correct set of statements is B, C, D, and E (Option 3).
105. List of endangered species was released by
1) WWF. 2) FOAM. 3) IUCN. 4. GEAC
The correct answer is:
3) IUCN (International Union for Conservation of Nature)
Explanation:
The IUCN Red List of Threatened Species is the most comprehensive inventory of the conservation status of biological species. It classifies species into different categories such as Endangered (EN), Critically Endangered (CR), Vulnerable (VU), and Extinct (EX) based on their risk of extinction.
106. What is the fate of a piece of DNA carrying only gene of interest which is transferred into an alien organism?
- The piece of DNA would be able to multiply itself independently in the progeny cells of the organism.
- It may be integrated into the genome of the recipient
- It may multiply and be inherited along with the host DNA
- The alien piece of DNA is not an integral part of chromosome
- It shows ability to replicate
Choose the correct answer from the option below:
- D and E only
- B and C only
- A and E only
- A and B only
Correct Answer: 2. B and C only
Explanation:
When a piece of DNA carrying a gene of interest is transferred into an alien organism, several outcomes are possible, but not all options provided are accurate. Let’s analyze each option:
- Option A: The piece of DNA would be able to multiply itself independently in the progeny cells of the organism.
- Incorrect. A piece of DNA, even if it carries a gene of interest, cannot multiply independently without being integrated into the host genome or being part of a self-replicating plasmid.
- Option B: It may be integrated into the genome of the recipient
- Correct. The transferred DNA can be integrated into the host genome through homologous recombination or other integration mechanisms, allowing it to become a stable part of the host’s genetic material.
- Option C: It may multiply and be inherited along with the host DNA
- Correct. If the DNA is integrated into the host genome or is part of a self-replicating plasmid, it can be replicated and inherited along with the host DNA during cell division.
- Option D: The alien piece of DNA is not an integral part of chromosome
- Incorrect in the context of integration. If the DNA is integrated into the host genome, it becomes an integral part of the chromosome.
- Option E: It shows ability to replicate
- Incorrect unless it is part of a self-replicating plasmid or integrated into the host genome. Naked DNA does not replicate on its own.
The correct answer is (B and C only), as these options accurately describe the potential fate of a piece of DNA carrying a gene of interest when transferred into an alien organism. It may be integrated into the host genome and, if so, can be replicated and inherited along with the host
107. Which of the following are required for the dark reaction of photosynthesis
- Light
- Chlorophyll
- CO2
- ATP
- NADPH
Choose the correct answer from the option given below:
- B, C and D only
- C, D and E only
- D and E only
- A, B AND C only
To answer this question, let’s break down the requirements for the dark reaction (also known as the Calvin cycle) of photosynthesis:
Dark Reaction Requirements:
- CO2 (Carbon Dioxide): This is the primary carbon source that is fixed into organic compounds during the Calvin cycle.
- ATP (Adenosine Triphosphate): Energy from ATP is used to drive the reactions in the Calvin cycle.
- NADPH (Nicotinamide adenine dinucleotide phosphate): This is a reducing agent produced in the light-dependent reactions and used in the Calvin cycle to reduce CO2 into organic compounds.
Options Analysis:
- A. Light: Not required directly in the dark reaction. Light is necessary for the light-dependent reactions, which produce ATP and NADPH used in the dark reaction.
- B. Chlorophyll: Essential for absorbing light in the light-dependent reactions but not directly involved in the dark reaction.
- C. CO2: Required for the dark reaction as it is the carbon source fixed into glucose.
- D. ATP: Required as an energy source.
- E. NADPH: Required as a reducing agent.
Correct Options:
- C. CO2
- D. ATP
- E. NADPH
The correct option for this answer is 2. C, D and E only
These are the components directly required for the dark reaction of photosynthesis.
108. The type of conservation in which the threatened species are taken out from their natural habitat and placed in species setting where they can be protected and given special care is called:
- Biodiversity conservation
- Semi-conservative method
- Sustainable development
- In-situ conservation
Analysis: No correct options are here, but we have to choose the answer. Lets see our analysis-
The correct option for the type of conservation described is not listed directly as described, but based on the definition provided, it aligns more closely with ex-situ conservation. However, since “ex-situ conservation” is not an option, let’s clarify the terms:
- Ex-situ conservation involves removing threatened species from their natural habitat and placing them in controlled environments like zoos, botanical gardens, or seed banks for protection and care. This matches the description given.
- In-situ conservation (Option 4) involves protecting species in their natural habitats.
- Biodiversity conservation (Option 1) is a broader term that encompasses various methods to preserve biodiversity.
- Sustainable development (Option 3) refers to meeting the needs of the present without compromising the ability of future generations to meet their own needs, which is not directly related to the specific conservation method described.
- Semi-conservative method (Option 2) is not a recognized term in conservation biology.
Given the options, none directly states “ex-situ conservation,” but based on the description, the closest correct concept is ex-situ conservation, which is not listed. However, if you must choose from the provided options, none accurately describe the method as defined. But if you’re looking for a term related to conservation in a controlled environment, you would typically look for “ex-situ conservation,” which is not an option here.
If you had to choose the least incorrect option based on the context of conservation, Option 1: Biodiversity conservation might seem like a broad category that could encompass ex-situ methods, but it’s not a precise match.
109. Given below are two statements:
Statement I: Bt toxin toxins are insect group specific and coded by a gene cry IAc
Statement II: Bt toxin exists as inactive protoxin in B. thuringnesis. However, after ingestion by the insect the inactive protoxin gets converted into active form due to acidic pH of the insect gut.
In the light of the above statements, choose the correct answer from the options given below:
- Both statement I and satement II are false
- Statement I is true but statement II is false
- Statement I is false but statement II is true
- Both statement I and satement II are true
Let’s analyze each statement logically: Read carefully following analysis and grasp the concept for future.
Statement I:
“Bt toxin toxins are insect group specific and coded by a gene cry IAc.”
- This statement is partially incorrect.
- Insect group specificity: True. Different Bt toxins target specific insect groups (e.g., Lepidoptera, Coleoptera, Diptera).
- Gene specificity: The statement implies that all Bt toxins are coded by cry IAc, which is false.
- cry IAc is just one of many genes encoding Bt toxins. Other genes like cry1Ab, cry3Aa, and cry4Ba also exist, each targeting different insects.
- cry IAc is specific to certain lepidopteran pests.
Statement II:
“Bt toxin exists as inactive protoxin in B. thuringiensis. However, after ingestion by the insect the inactive protoxin gets converted into active form due to acidic pH of the insect gut.”
- This statement is false.
- Existence as inactive protoxin: True. Bt toxins are produced as inactive protoxins in B. thuringiensis.
- Activation mechanism: False. The activation occurs in the alkaline midgut (pH 9–12) of susceptible insects, not due to acidic pH.
- The alkaline environment dissolves the crystalline protoxin, and midgut proteases cleave it into the active toxin.
Conclusion:
- Statement I is incorrect because it inaccurately suggests all Bt toxins are encoded by cry IAc.
- Statement II is incorrect because it incorrectly states that the protoxin is activated by acidic pH.
Final Answer:
Option 1 (Both statement I and statement II are false) is correct.
110. A transcription unit in DNA is defined primarily by the three regions in DNA and these are with respect to upstream and down stream ends
- Structural gene, Transposons, Operator gene
- Inducer, Repressor gene and Terminator
- Promoter, Structural gene, Terminator
- Repressor, Operator gene, Structural gene
The correct answer is: 3. Promoter, Structural gene, Terminator
Logical Explanation:
A transcription unit in DNA is defined by three key regions that are essential for the process of transcription, with respect to upstream and downstream ends:
- Promoter:
- The promoter is located upstream of the structural gene.
- It is the site where RNA polymerase binds to initiate transcription.
- It determines the start point and direction of transcription.
- Structural Gene:
- This region contains the coding sequence that is transcribed into RNA.
- It provides the template for RNA synthesis.
- Terminator:
- The terminator is located downstream of the structural gene.
- It signals the end of transcription, causing RNA polymerase to stop and release the newly synthesized RNA.
Why Other Options Are Incorrect:
- Structural gene, Transposons, Operator gene:
- Transposons and operator genes are not part of a transcription unit. Operators are regulatory elements in operons, and transposons are mobile genetic elements.
- Inducer, Repressor gene, Terminator:
- Inducers and repressors are regulatory molecules or genes but are not structural components of a transcription unit.
- Repressor, Operator gene, Structural gene:
- Repressors and operators are part of regulatory mechanisms (e.g., in operons) but are not components of a transcription unit.
Thus, Promoter, Structural gene, Terminator (Option 3) correctly defines the primary regions of a transcription unit.