Some characters are controlled by cytoplasmic genes present in mitochondria and chloroplast because in zygote cytoplasm is derived from egg (female parent) and DNA is maternally transmitted. Therefore, inheritance is known as maternal inheritance. Example: In reciprocal cross of two trains which have AA and BB genotype and a and b cytoplasm, two hybrids AB(a) and AB(b) having different nuclear genotype will produce. AB (a) will resemble strain A or AA. AB (b) will resemble strain B or BB.