{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

nov 15 - Handout Extranuclear inheritance in eukaryotes In...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Handout- Extranuclear inheritance in eukaryotes November 15, 2006 In eukaryotes the transmission of traits between generations is dominated by the nuclear genes. However, a small subset of genes ( e.g. 1 in a 1000 for humans) is located on the chromosomes of cytoplasmic organelles – mitochondria and plastids, as typified by chloroplasts. Mitochondria are a universal feature of eukaryotes, and chloroplasts are present in the cells of plants, algae, and some protists. These ‘extranuclear’ genes are organized somewhat differently than the nuclear DNA, and as a consequence they show patterns of inheritance that do not obey Mendel’s laws. Because cpDNA and mtDNA are generally inherited maternally, comparisons of the base sequences in organelle DNA of different organisms can provide complementary evolutionary information to studies of nuclear DNA. We have also become interested in mtDNA mutations associated with human disorders. Learning Goals Mitochondrial and chloroplast genomes are relatively small; they each contain only a few dozen genes, typically located on a single chromosome; and they are present in hundreds or thousands of copies per cell. •Review the Endosymbiotic Theory for the evolutionary origin of mitochondria and chloroplasts. What features of mitochondrial and chloroplast genetics support this theory? •A mitochondrion is composed of hundreds of different RNAs and protein, yet its own genome only contains a few dozen genes. How is this possible? Many mitochondrial proteins are encoded by nuclear genes—how did this evolve? •Why is the genotype of a mitochondrial gene potentially more variable than that of a nuclear gene? What is the meaning of the terms ‘homoplasmic’ and ‘heteroplasmic’? •When is the mitochondrial genome replicated, and how is it subdivided between daughter cells at mitosis? If a cell is heteroplasmic and undergoes mitosis, will its daughter cells have the exact same mitochondrial genotype? If a zygote (= fertilized egg) is heteroplasmic, will the cells of the adult produced that zygote have the same mitochondrial genotype? •Mitochondrial inheritance in humans is typical of that in most animal species, i.e. the mother contributes ~99.9% and the father ~0.1% of the offspring’s mitochondrial DNA. Why is this contribution so heavily biased towards the mother? How can a mother produce different offspring who
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern