Acetohydroxy acid synthase (AHAS), an enzyme involved in branched-chain amino acid biosynthesis, is inhibited by all the following classes of herbicides, EXCEPT:
The correct answer is (b).
L-phosphinothricin. While L-phosphinothricin is an herbicide that inhibits glutamine synthetase (not AHAS), it does not inhibit acetohydroxy acid synthase (AHAS).
Incorrect options-
Imidazolinones (a), Sulfonylureas (c), and Triazolopyrimidines (d) all directly inhibit AHAS enzyme, causing inhibition of branched-chain amino acid synthesis.
Given below are the different stages of Arabidopsis embryogenesis (Column X) and their characteristic patterns of cell division (Column Y).
Column X
A. Zygotic
B. Globular
C. Heart
D. Torpedo
Column Y
i. Formation of an 8-cell embryo, exhibiting radial symmetry and undergoing additional cell division to create the protoderm
ii. Polarized growth of cells followed by a symmetric transverse division giving rise to a small apical cell and an elongated basal cell
iii. Cell elongation and cellular differentiation processes throughout the embryonic axis with visible distinction between the adaxial and abaxial tissue of the cotyledons
iv. Focused cell division forming two cotyledons, giving bilateral symmetry to the embryo
Which one of the following options represents the correct match between Column X and Column Y?
The taxon cycle is the predicted, progressive ecological and evolutionary changes in the descendants of founding populations. Taking the case of insular biotas, the figure can be used to conceptualize and predict species types (a, b, c, d, e, f, g, h) based on their fundamental capacities to evolve, immigrate, and persist.
The table below has species types (Column X) and the possible traits (Column Y) associated with each type.
Which one of the following options represents all correct matches between Column X and Column Y?
In amphibians and fish, the cells of the organizer ultimately contribute to i) pharyngeal endoderm, ii) head mesoderm, iii) dorsal mesoderm, and iv) dorsal blastopore lip. The following statements are made about the function of the organizer and its derivatives:
A. The pharyngeal endoderm and pre-chordal plate prevent formation of forebrain and midbrain.
B. The organizer has the ability to dorsalize the ectoderm and induce formation of the neural tube.
C. The dorsal mesoderm inhibits induction of the hindbrain and trunk.
D. The organizer tissue possesses the ability to dorsalize the surrounding mesoderm into somite-forming mesoderm.
Which one of the following options is a combination of all correct statements?
To test if viral proteins are transported between Golgi stacks in vesicles or are released into the cytosol by one Golgi stack and taken up by another, viral protein transport was examined between Golgi stacks of infected and uninfected cells. Which one of the following experimental designs would best distinguish these two hypotheses?
The following statements are made regarding colchicine treatment in plants for inducing polyploidy.
A. In colchicine-treated cells, sister chromatids cannot separate during anaphase, leading to chromosome doubling when the nucleus reforms.
B. Colchicine stimulates endoreduplication in the treated cells, bypassing cytokinesis to yield polyploid cells in a process called “C-mitosis”.
C. In sterile interspecific hybrids, colchicine treatment may restore fertility by converting them into amphipolyploids.
D. Colchicine treatment during meiosis has no effect, as it only acts on mitotic cells.
E. Colchicine binds to tubulin and prevents spindle fibre formation during mitosis.
Which one of the following options represents a combination of all correct statements?
ENZ function prevents premature differentiation of mouse neural stem cells. Kinase inhibitor treatment differentiates these cells prematurely. This is prevented if a specific serine-to-aspartate (S to D) mutation is introduced in ENZ. Based on this information, which one of the following statements is INCORRECT?
The following statements are made regarding bioremediation and phytoremediation:
A. Phytovolatilization can reduce soil contamination but may create secondary pollution in the atmosphere.
B. In rhizofiltration, plants are effective only if their roots are exposed to contaminated soil.
C. Phytostabilization reduces contaminant mobility, but the total pollutant load in the soil remains unchanged.
D. Bioventing involves the injection of air or oxygen into soil to stimulate aerobic microbial degradation.
E. During in situ bioaugmentation, the remediation is achieved by physically removing contaminated soil for off-site treatment and replacing it with decontaminated soil.
Which one of the following options represents a combination of all INCORRECT statements?
In standard or batch cultures, cells are grown in a fixed volume of medium. As they grow, nutrients are consumed and metabolites accumulate. Eventually, cultures may stop growing because of nutrient depletion and accumulation of toxic products. The following procedures may prolong the life of batch cultures:
A. Gradual addition of fresh medium and increasing volume of the culture
B. Replacing a constant fraction with an equal volume of fresh medium
C. Occasional removal of used medium and reducing growth factors in the medium
D. Intermittently adding serum and growth factors to the medium
Which one of the following combinations will ensure healthy growth of cells in culture?
Which one of the following statements about evolution of the vertebrate brain is most accurate?
In a polluted aquatic environment, bacteria are chronically exposed to low concentrations of multiple antibiotics released from pharmaceutical effluents. Over time, resistant colonies appear even when the antibiotic concentration remains constant. To determine whether resistance arises through induced mutation (a physiological response to antibiotics) or random mutation followed by selection, an ecologist performs a fluctuation test similar to that of Luria and Delbrück (1943) using replicate bacterial cultures.
Which one of the following outcomes would best support the conclusion that antibiotic resistance arises by random mutation followed by selection, rather than by induction?
