Q90. What is the central purpose of genome annotation?
[RAS / RPSC — Practice]
- (a) Convert every gene to protein in vitro
- (b) Identify and describe genes and other functional sequence features
- (c) Remove all noncoding DNA
- (d) Replace chromosomal centromeres
Answer: (b) Identify and describe genes and other functional sequence features
Explanation: Genome annotation assigns biological information to DNA sequences, including gene boundaries, coding regions, RNA genes and regulatory features. Automated predictions are improved by experimental evidence. Annotation turns a sequence assembly into a resource that scientists can interpret.
Q89. Cas9, frequently mentioned alongside CRISPR, is best described as which of the following?
[UPSC CSE (Pre) 2019]
- (a) A DNA-cutting endonuclease guided by RNA
- (b) A protein that translates messenger RNA
- (c) An antibody against bacterial toxins
- (d) A hormone derived from yeast
Answer: (a) A DNA-cutting endonuclease guided by RNA
Explanation: Cas9 is an RNA-guided nuclease that cleaves DNA at a chosen target adjacent to a compatible PAM. CRISPR guide RNA provides sequence specificity. Its molecular-scissor action enables precise gene editing, though repair outcomes require experimental control.
Q88. Genome-wide association studies usually seek associations between:
[SSC CGL — Practice]
- (a) Cell size and optical wavelength only
- (b) Rainfall and rock hardness
- (c) Blood pressure and latitude alone
- (d) Genetic variants and measured traits or diseases
Answer: (d) Genetic variants and measured traits or diseases
Explanation: Genome-wide association studies test many genetic variants across a population to locate statistically associated regions. These associations may highlight biological pathways, but an associated variant is not automatically causal. Population structure and multiple testing require careful adjustment.
Q87. What is a single-nucleotide polymorphism (SNP)?
[SSC CHSL — Practice]
- (a) Exchange of a complete organ
- (b) Deletion of an entire species
- (c) A common variation at one nucleotide position
- (d) An enzyme that joins DNA fragments
Answer: (c) A common variation at one nucleotide position
Explanation: An SNP is a sequence variant at a single genomic position occurring at appreciable frequency in a population. SNPs are useful markers for mapping traits, investigating ancestry and studying disease susceptibility. Most SNPs are not directly harmful.
Q86. In sequence comparison, homology means that genes or sequences:
[SSC MTS — Practice]
- (a) Have equal length with no exceptions
- (b) Share a common evolutionary ancestry
- (c) Occur only in plants
- (d) Always perform the same biochemical function
Answer: (b) Share a common evolutionary ancestry
Explanation: Homologous sequences descend from a common ancestral sequence. Their similarity may indicate related functions, but functions can diverge after duplication or speciation. Homology is an evolutionary relationship, not simply a numerical percentage of sequence identity.
Q85. RNA interference (RNAi) technology suppresses gene expression principally through which mechanism?
[UPSC CSE (Pre) 2019]
- (a) Silencing complementary RNA molecules
- (b) Forming new ribosomes
- (c) Increasing DNA methylation in every gene
- (d) Amplifying target chromosomes
Answer: (a) Silencing complementary RNA molecules
Explanation: RNA interference uses short RNA molecules to guide protein complexes towards complementary messenger RNA. The targeted RNA is degraded or its translation blocked. This reduces expression of a selected gene without necessarily changing the underlying DNA sequence.
Q84. Which technique is chiefly used to compare thousands of gene-expression measurements simultaneously?
[RRB NTPC — Practice]
- (a) Gravimetric ash testing
- (b) Simple hand lens inspection
- (c) Rain gauge measurement
- (d) Expression microarray or RNA sequencing
Answer: (d) Expression microarray or RNA sequencing
Explanation: Microarrays and RNA sequencing measure expression across many genes within a sample. Researchers compare expression patterns among tissues or treatments to identify biological responses. RNA sequencing additionally detects transcripts without requiring every transcript to have a predesigned probe.
Q83. An organism’s complete protein complement under specified conditions is called its:
[RRB Group D — Practice]
- (a) Plasmidome only
- (b) Karyotype
- (c) Proteome
- (d) Cytoskeleton
Answer: (c) Proteome
Explanation: The proteome includes proteins expressed in a cell, tissue or organism under defined conditions. Unlike a relatively stable genomic sequence, protein abundance and modification can change rapidly. Proteomics investigates these molecules, often using mass spectrometry.
Q82. The main target of Bt cotton technology is resistance against:
[CGPSC — Practice]
- (a) All bacterial diseases
- (b) Certain insect pests, including bollworms
- (c) Every weed species
- (d) Drought in all conditions
Answer: (b) Certain insect pests, including bollworms
Explanation: Bt cotton expresses selected insecticidal Cry proteins from Bacillus thuringiensis. These proteins affect particular susceptible insects, including important bollworm pests. They do not confer universal resistance to all insects, diseases or environmental stresses.
Q81. DNA fingerprinting depends most fundamentally upon which feature?
[RAS / RPSC (Pre) 2018]
- (a) Genetic polymorphism
- (b) Constant chromosome length
- (c) Identical mitochondrial genomes
- (d) Uniform DNA sequences
Answer: (a) Genetic polymorphism
Explanation: DNA polymorphism denotes heritable sequence differences among individuals. Variation in short tandem repeats and other markers forms distinguishing DNA profiles. Since profiles are inherited, the same data can help resolve biological relationships as well as forensic identity.
