Traits controlled by organellar dna do not show mendelian inheritance because

In mendelian inheritance, the alleles for a gene show normal dominant-recessive relationship. Chromosomes also show crossover due to which new random combination of traits is possible in the offspring. This crossover takes place between homologous chromosomes during meiosis I.

Organellar DNA like the ones present in mitochondria and chloroplast do not follow mendelian inheritance because unlike nuclear chromosomes they do not have cross over events. There is no orderly segregation of alleles during meiosis. Traits controlled by them are usually inherited as it is and usually it is from the maternal parent because paternal gamete like sperm does not contain mitochondria.