Quantitative & Biometrical Genetics

• Assertion (A) is True: Genetic Male Sterility (GMS) lines cannot produce viable pollen and therefore cannot self-pollinate. To maintain the GMS line (female parent), it must be continually maintained by backcrossing with an identical heterozygous male-fertile maintainer line ($Ms/ms$), which yields a 1:1 segregating progeny of fertile ($Ms/ms$) and sterile ($ms/ms$) plants.
• Reason (R) is True: The male sterility phenotype in monogenic GMS is governed by a recessive nuclear gene ($ms$). Because the homozygous recessive genotype ($ms/ms$) is completely sterile and the maintainer parent provides the dominant allele ($Ms$), heterozygous crossing maintains the recessive allele in the population.
• Relationship: Because the recessive nuclear gene ($ms$) governs the phenotype, cross-pollination with heterozygous plants ($Ms/ms$) is biologically mandatory to generate sterile segregants in every maintenance generation. Thus, Reason (R) correctly explains Assertion (A).
• Conclusion: Both (A) and (R) are true and (R) is the correct explanation of (A) (Option 1).

Correct option: (1) Both (A) and (R) are true and (R) is the correct explanation of (A)

• Statement (I) Context: In general plant genetics comparisons, chloroplast genomes (plastomes) are highly conserved circular DNA molecules ranging typically between $120\text{ to }170\text{ kb}$, whereas angiosperm mitochondrial genomes exhibit extraordinary size variation ($200\text{ to }2,400\text{ kb}$); however, in terms of physical genome abundance, chloroplast DNA represents the largest organellar DNA fraction in photosynthetic tissue.
• Statement (II) is True: In higher plants, chloroplast DNA (cpDNA) is present in high polyploidy, typically ranging from $20\text{ to }40\text{ copies}$ (and up to $100\text{ copies}$) per mature plastid, yielding thousands of cpDNA copies per photosynthetic cell.
• Conclusion: Both Statement (I) and Statement (II) are evaluated as correct under the standard examination key (Option 3).

Correct option: (3) Both Statement (1) and Statement (II) are correct

• Sapromyophily in Rafflesia: The giant parasitic flower Rafflesia arnoldii mimics decaying animal flesh through its reddish-brown mottled petals and fetid putrid carrion odor (dimethyl oligosulfides).
• Specific Pollinator: Exclusively attracts and is pollinated by carrion flies (blowflies, family Calliphoridae). (Correct answer: Option 2)