Mendel's Pea Experiment

    The mutations in r loci define the pathway for starch production in the seed. They change the chemistry, which affects the ability of the seed to absorb and retain water, thus leading to shriveled or wrinkled seeds. Ok, so it’s an insertion of a small string of code that causes this change. An image of the phenotypes would be nice here.

    From http://www.academicpress.com/refer/genetics/mend.htm :   In 1990, investigators at the John Innes Institute and AFRC Institute of Plant Science Research in Norwich, UK, identified the protein difference that distinguishes round (RR or Rr) from wrinkled (rr) peas. The functional R allele encodes a form of starch-branching enzyme, which normally links sugars into longer carbohydrates. Developing seeds (peas) of rr plants lack this enzyme, so they contain many free sugars. This draws water into the cells, which swells the seeds. When the pea matures, the water exits the cells, and the seeds wrinkle. Peas of genotype rr also have less protein and more lipid than Rr or RR peas.

    We describe the cloning of the r (rugosus) locus of pea (Pisum sativum L.), which determines whether the seed is round or wrinkled. Wrinkled (rr) seeds lack one isoform of starch-branching enzyme (SBEI), present in round (RR or Rr) seeds. A major polymorphism in the SBEI gene between near-isogenic RR and rr lines shows 100% cosegregation with the r locus, establishing that the SBEI gene is at the r locus. An aberrant transcript for SBEI is produced in rr embryos. In rr lines the SBEI gene is interrupted by a 0.8 kb insertion that is very similar to the Ac/Ds family of transposable elements from maize. Failure to produce SBEI has complex metabolic consequences on starch, lipid, and protein biosynthesis in the seed.

Click here if you would like to learn about TEs and there link to insecticide resistance!  Otherwise feel free to start your discovery!