Which of the following best explains why genes located in mitochondria and chloroplasts do not exhibit Mendelian patterns of inheritance?

• A. They are only expressed in somatic cells and not passed to offspring.
• B. They are always silenced by nuclear gene regulation.
• C. They are inherited primarily through the maternal lineage, rather than through both parents equally.
• D. They undergo frequent recombination during meiosis, leading to unpredictable inheritance.

Answer: (C)

Verified step by step guidance

1. Understand that Mendelian inheritance typically involves genes located in the nucleus, where alleles segregate and assort independently during meiosis, leading to predictable inheritance patterns.
2. Recognize that mitochondria and chloroplasts have their own DNA, separate from nuclear DNA, and these organelles are inherited differently compared to nuclear genes.
3. Recall that mitochondria and chloroplasts are usually inherited maternally because the egg contributes most of the cytoplasm (and thus these organelles) to the offspring, while the sperm contributes very little or none.
4. Note that because of this maternal inheritance, genes in mitochondria and chloroplasts do not follow the typical Mendelian patterns of inheritance, which assume biparental contribution of alleles.
5. Conclude that the key reason for non-Mendelian inheritance of mitochondrial and chloroplast genes is their uniparental (maternal) inheritance, rather than recombination or gene silencing.