Biotechnology: UPSC Previous Year Questions (Science and Technology)

Explanation

Viruses are obligate intracellular parasites, meaning they require a host cell to replicate. They can infect bacteria, fungi, plants, animals, and other viruses. Viruses that infect bacteria are called bacteriophages (or simply phages). These viruses play a crucial role in regulating bacterial populations. Phages attach to bacterial cells, inject their genetic material, and hijack the bacterial machinery to replicate themselves. This process often leads to the destruction (lysis) of the bacterial cell. Viruses that infect fungi are called mycoviruses (Mycophages). They do not have an extracellular phase (i.e., they lack the ability to move outside fungal cells). They are linked to plant diseases because they weaken fungi that help plant growth. Cryphonectria hypovirus 1 (CHV1) infects chestnut blight fungus (Cryphonectria parasitica). Plant viruses are well-known pathogens that cause significant economic losses in agriculture such as the Tobacco Mosaic Virus (TMV), Potato Virus Y (PVY), and Tomato Spotted Wilt Virus (TSWV). Plant viruses are typically transmitted by insects, nematodes, or through contaminated seeds and tools. They infect plant cells disrupting their normal cellular functions and cause symptoms such as leaf curling, stunting, and mosaic patterns.

Explanation

Option (b) is correct: A transcriptome is the full range of messenger RNA(mRNA) molecules expressed by an organism. The term "transcriptome" can also be used to describe the array of mRNA transcripts produced in a particular cell or tissue type. Transcriptome analysis (RNA sequencing or RNA-Seq) is a key tool in bioinformatics for studying gene expression, identifying biomarkers, and understanding cellular functions.

Option (a), (c) and (d) are incorrect:

Genome editing involves enzymes like CRISPR-Cas9, TALENs, etc which are used to modify DNA sequences. These enzymes are tools for targeted genetic modifications. Transcriptome doesn’t relate to enzymes used in editing Gene expression involves the processes of transcription (DNA to mRNA) and translation (mRNA to proteins). It includes regulatory mechanisms like transcription factors, epigenetic modifications, and post-transcriptional processing. Mutations are changes in the DNA sequence caused by errors during replication, environmental factors, or chemical agents.