Chapter 17. Inheritance of Sex Chromosomes, Linked Genes, and Organelles

Mitochondrial and chloroplast genomes often show uniparental inheritance.

During sexual reproduction, organelles do not show the regular, highly choreographed movements that chromosomes undergo during Mendelian segregation. Organelles are partitioned to the gametes along with other cytoplasmic components, and therefore their mode of inheritance depends on how the gametes are formed, how much cytoplasm is included in the gametes, and the fate of the cytoplasm in each parental gamete after fertilization.

Considering the great diversity in the details of reproduction in different groups of organisms, it is not surprising that there is a diversity of types of inheritance of cytoplasmic organelles. The three most important types are:

Maternal inheritance, in which the organelles in the offspring cells derive from those in the mother.
Paternal inheritance, in which the organelles in the offspring cells derive from those in the father.
Biparental inheritance, in which the organelles in the offspring cells derive from those in both parents.

In most organisms, either maternal inheritance or paternal inheritance predominates, but sometimes there is variation from one offspring to the next. For example, transmission of the chloroplasts ranges from strictly paternal in the giant redwood Sequoia, to strictly maternal in the sunflower Helianthus, to either maternal or paternal (or less frequently biparental) in the fern Scolopendrium, to mostly maternal but sometimes paternal or biparental in the snapdragon Antirrhinum.

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There is likewise great diversity among organisms in the inheritance of mitochondrial DNA. Most animals show maternal transmission of the mitochondria, as would be expected from their large, cytoplasm-rich eggs and the small, cytoplasm-poor sperm. Among other organisms, there is again much variation, including maternal transmission of mitochondria in flowering plants and paternal transmission in the green alga Chlamydomonas.