Q.38 Among the following, which genetic material is naturally inherited through maternal inheritance in

higher plants?

(A) Nuclear DNA

(B) Plasmid DNA

(C) Chloroplast DNA

(D) T-DNA

The correct answer is: (C) Chloroplast DNA. In most higher plants, chloroplast genes are a classic example of cytoplasmic (extranuclear) genetic material that shows predominantly maternal inheritance.​

Detailed explanation of each option

Option (A) Nuclear DNA

• Nuclear DNA resides in chromosomes inside the nucleus and follows Mendelian inheritance, where alleles are contributed by both parents through meiosis and fertilization.​

• In higher plants, nuclear genes are therefore typically biparentally inherited, not strictly maternal, although dosage and imprinting effects can occur in some cases.​

Hence, nuclear DNA is not the correct choice for natural, regular maternal inheritance in higher plants.

Option (B) Plasmid DNA

• Plasmids are small, usually circular, extrachromosomal DNA molecules common in bacteria and some lower eukaryotes, and are the basis of many cloning vectors.​

• Higher plants do not commonly maintain stable, naturally occurring autonomous plasmids in the same way bacteria do; plant transformation vectors (Ti plasmid, Ri plasmid) belong to Agrobacterium, not to the plant itself.​

Therefore, plasmid DNA is not the typical, naturally inherited maternal genetic system in higher plants.

Option (C) Chloroplast DNA – Correct

• Chloroplasts contain their own circular genome, commonly called chloroplast DNA (cpDNA) or plastid DNA, located in the stroma of the organelle.​

• In most higher plants, chloroplasts and their DNA are inherited uniparentally, usually from the maternal parent, because the egg contributes the bulk of the cytoplasm, while the sperm (pollen) contributes mostly nuclear DNA.​

• Classic examples include leaf variegation in Mirabilis jalapa and many other cases of plastid inheritance, where the phenotype of the progeny follows the maternal parent due to cytoplasmic (chloroplast) genes.​

Thus, chloroplast DNA is a classic and widely accepted example of maternal inheritance in higher plants, making (C) the correct answer.

Option (D) T-DNA

• T-DNA (Transferred DNA) is the segment of the Ti plasmid from Agrobacterium tumefaciens that is transferred into plant cells during infection and integrates into the plant nuclear genome.​

• Once integrated, T-DNA behaves like part of the nuclear DNA and is inherited by the usual Mendelian rules, not specifically or obligatorily through the maternal line.​

Therefore, T-DNA is not a natural, cytoplasmically localized genetic system and does not show obligatory maternal inheritance.

Why chloroplast DNA shows maternal inheritance

• Cytoplasmic inheritance (also called organellar inheritance) involves genes located in organelles such as mitochondria and chloroplasts, which are present in the egg cytoplasm in much larger numbers than in sperm.​

• In most angiosperms, pollen either lacks functional plastids or its plastids are excluded/degraded during gamete formation, leading to chloroplast genomes being transmitted almost exclusively via the ovule (maternal parent).​

• Although some plant groups (e.g., certain conifers) show paternal or biparental plastid inheritance, the general rule for “higher plants” in classical genetics and exam context is maternal inheritance of chloroplast DNA.​

Hence, for CSIR-NET/competitive exams, (C) Chloroplast DNA is the standard correct option.

SEO-friendly introduction

Maternal inheritance in higher plants is a fundamental concept in genetics and plant breeding, closely linked to cytoplasmic or organellar DNA. In multiple-choice questions on exams like CSIR NET, GATE, and other life science tests, chloroplast DNA is classically tested as the genetic material that follows maternal inheritance patterns. Understanding why chloroplast DNA is correct—and why nuclear DNA, plasmid DNA, and T-DNA are not—is crucial for solving such questions accurately and mastering cytoplasmic inheritance concepts.​