PLSC 631 - Intermediate Genetics
Maternal Inheritance and Maternal Effects Quiz
1. Students in your genetics class observe a new mutant of Arabidopsis. This plant has vertical white stripes in the leaves that run parallel with the mid-vein. These adventuresome students cross the mutant (as the female) and a wild-type, green plant. The F1 and F2 plants were all striped. What experiments would you perform further to sort the inheritance of the green/striped leaf color pattern? (This is a hypothetical example.)
2. Chlamydomonas is a single-celled haploid algae that contains a single large chloroplast. Further, it is relatively easy to manipulate Chlamydomonas in culture. For meiosis to occur, two haploid cells fuse. Fusion only occurs between cells of the opposite mating types (mt+ and mt-). Streptomycin-resistance Chlamydomonas cell lines have been developed, and these cell lines can be screened in culture. The symbols used are: Streptomycin resistant = str-r; Streptomycin sensitive = str-s. The following are the results of two matings. From these results, propose a genetic explanation for the inheritance of streptomycin-resistance.
| Cross | Result |
|---|
| str-r, mt+ x str-s, mt- | all progeny cells are str-r |
| str-s, mt+ x str-r, mt- | all progeny cells are str-s |
3. Two strains of corn were screened with a DNA probe. Strain 1 contained a 4 kb fragment that hybridized with the probe, and strain 2 contained a 2 kb strain that was recognized by the probe. Two crosses were made (the female is listed first): Cross 1 - Strain 1 x Strain 2 ===> all progeny contained the 4 kb fragment; Cross 2 - Strain 2 x Strain 1 ===> all progeny contained the 2 kb fragment. When the progeny of cross 1 were crossed as females to strain 2 all of the progeny contained the 4 kb fragement. Why were the backcrosses performed, and information was gained regarding the cellular location of the DNA to which the probe hybridized? If the progeny of cross two were mated as females to strain 1, predict the size of DNA fragement to which the probe would bind? What information lead you to this conclusion?
4. Male sterility/fertility in corn is controlled by nuclear and cytoplasmic factors. a. If a male sterile female is pollinated by a plant heterozygous for Rf, what are the genotypes and phenotypes of the progeny with respect to the cytoplasmic and nuclear genes?
b. In addition to the original restorer of fertility gene, Rf1, a second independently assorting restorer gene, Rf2 was found in corn. A male sterile female was crossed with plants with the following genotypes. What segregation patterns would you expect from each mating?
| Mating | Cross |
|---|
1 | Male sterile female x Rf1rf1Rf2rf2male |
2 | Male sterile female x Rf1Rf1rf2rf2 male |
3 | Male sterile female x rf1rf1Rf2rf2 male |
| 4 | Male sterile female x Rf1rf1Rf2Rf2 male |