Exercises: Nuclear and Non-Nuclear Inheritance

Name two organelles in a eukaryotic cell that contain their own DNA, and state which kingdoms of organisms have each.

In humans, mitochondria in the zygote are inherited almost entirely from one parent.

1. a) State which parent contributes the mitochondria.

1. b) Explain briefly why this is the case.

Mitochondrial DNA (mtDNA) is a small, circular, double-stranded molecule.

1. a) State two ways in which mtDNA differs from nuclear DNA in structure.

1. b) State one way in which the mtDNA is similar to the DNA of prokaryotes.

1. c) Explain how this similarity supports the endosymbiotic theory.

mtDNA is used in forensic science and in tracing maternal ancestry, for example in the identification of remains.

1. a) Explain why mtDNA can be used to trace maternal lineages over many generations.

1. b) Explain why mtDNA can sometimes be recovered from degraded samples when nuclear DNA cannot.

1. c) Explain one limitation of using mtDNA alone to identify an individual.

Mitochondrial replacement therapy (sometimes called "three-parent baby" techniques) replaces a mother's faulty mitochondria with healthy donor mitochondria.

1. a) Explain how this technique could prevent a child inheriting a mitochondrial disorder.

1. b) State which genetic information the child inherits from the donor and which from the parents.

1. c) Discuss one ethical issue raised by this technique.