Mitochondrial and chloroplast inheritance Transitional Reasoning Practice

Questions

1. 1.

   A researcher investigates leaf pigmentation in a flowering plant species where chloroplasts are known to be transmitted through the cytoplasm of the egg cell. In Cross 1, pollen from a pale-yellow mutant strain is applied to the carpels of a wild-type dark-green strain, producing offspring that all develop dark-green leaves. In Cross 2, the reciprocal cross is performed using pollen from the dark-green strain to fertilize ovules from the pale-yellow mutant strain. Which prediction and underlying mechanism correctly identify the phenotype of the offspring resulting from Cross 2?

   • A) All offspring will have dark-green leaves because the nuclear allele responsible for chlorophyll synthesis is fully dominant.
   • B) The offspring will yield a 3:1 ratio of dark-green to pale-yellow plants because organellar alleles segregate during meiosis.
   • C) All offspring will have pale-yellow leaves because chloroplast genomes are inherited maternally through the ovule cytoplasm.
   • D) Approximately half of the offspring will be pale-yellow and half dark-green because chloroplast genomes assort independently at fertilization.

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