AI-generated explanation. Check against your textbook.
Explanation:
Viroids are tiny infectious agents consisting only of a short strand of RNA. They do not have a protein coat (capsid). Therefore they are naked RNA, free of any protein envelope. This matches option 2: “They have free RNA without protein coat.”
🧠 Did You Know?
Viroids are smaller than viruses and affect plants by interfering with their normal metabolism, without encoding proteins.
💡 NCERT Memory Line:
Viroids are naked RNA without a protein coat; they are infectious RNA particles lacking a capsid.
AI-generated explanation. Check against your textbook.
Explanation:
The incorrect statement is option 2. In NCERT, the infective part of a virus is its nucleic acid (DNA or RNA), not the protein coat. The protein coat (capsid) encases the nucleic acid but is not itself the genetic material. Hence, viruses are obligate parasites that need a host to reproduce. Viroids lack a protein coat, and prions are infectious proteins with no nucleic acid, consisting only of abnormally folded proteins.
🧠 Did You Know?
NCERT emphasizes that the key infectious nature of viruses lies in their nucleic acid, while prions are misfolded proteins and viroids are naked RNA without a capsid.
💡 NCERT Memory Line:
Viruses have nucleic acid enclosed in a protein coat; infective material is nucleic acid.
AI-generated explanation. Check against your textbook.
Explanation:
Persistent nucellus in the seed is called perisperm. In some seeds, the nucellus remains as a food reserve and forms the main part of the seed’s nutritive tissue, instead of developing into endosperm.
🧠 Did You Know?
Perisperm is seen in seeds of some plants like certain types of peppers and black pepper, where the nucellus does not degenerate.
💡 NCERT Memory Line:
Persistent nucellus = perisperm; chalaza, hilum, and tegmen refer to other parts: chalaza (attachment region), hilum (seed scar), tegmen (outer seed coat layer).