Mitochondrial and chloroplast inheritance Transitional Reasoning Download PDF

Questions

1. 1.

   A researcher investigates leaf pigmentation in a flowering plant species and performs reciprocal crosses between a mutant variegated line and a homozygous wild-type green line. When pollen from the variegated mutant fertilizes ovules of the wild-type green parent, all resultant $F_1$ offspring display normal green leaves. However, when reciprocal fertilization is carried out using pollen from the wild-type green parent onto flowers of the variegated mutant, the offspring exhibit a mixture of variegated, green, and non-pigmented phenotypes that fail to segregate into standard Mendelian ratios. Based on these observations, which conclusion best explains the inheritance pattern of this trait?

   • A) The gene controlling the trait is located on chloroplast DNA and transmitted uniparentally through maternal cytoplasm.
   • B) The variegated phenotype is governed by an X-linked recessive allele that undergoes random X-chromosome inactivation.
   • C) The trait is determined by an autosomal dominant nuclear gene exhibiting variable expressivity and incomplete penetrance.
   • D) The pigmentation defect arises from a genomic imprinting mechanism where the paternal allele is epigenetically silenced.