6. Mendel’s laws of inheritance is applicable to-
(1) Nuclear genes (2) Plasmid genes
(3) Mitochondrial genes (4) Plastid genes
Why nuclear genes fit Mendel’s laws
Mendel’s laws (dominance, segregation, independent assortment) are based on:
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Genes existing as pairs of alleles in diploid nuclei.
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Equal, biparental contribution of chromosomes to the zygote.
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Segregation of homologous chromosomes and independent assortment at meiosis.
These conditions are fulfilled by nuclear genes located on autosomes or, with some modifications, on sex chromosomes. Nuclear genes typically show the classical 3:1, 9:3:3:1 Mendelian ratios in controlled crosses.
So option (1) Nuclear genes is correct.
Why the other options are not Mendelian
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Plasmid genes
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Plasmids are extra-chromosomal DNA, common in bacteria and some eukaryotes.
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They often show uniparental or horizontal transfer, copy-number variation, and segregation patterns that do not follow simple allele-pair behavior, so they are usually non-Mendelian.
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Mitochondrial genes
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In most animals and many plants, mitochondria are inherited maternally.
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All offspring of an affected mother can inherit the mutation, while offspring of an affected father usually do not, producing cytoplasmic inheritance patterns, not Mendelian segregation.
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Plastid genes (chloroplast genes)
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Like mitochondrial DNA, plastid genomes are often passed uniparentally (usually maternal), leading to non-Mendelian, cytoplasmic inheritance (e.g., variegated leaves).
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They do not assort and segregate like paired nuclear alleles in meiosis.
Therefore, Mendel’s laws of inheritance are applicable primarily to nuclear genes, not to plasmid, mitochondrial, or plastid genes.
