Maternal Inheritance and Maternal Effects Quiz

PLSC 631 - Intermediate Genetics

Maternal Inheritance and Maternal Effects Quiz

1. From your experience as a geneticist, you are aware that variegation of leaf tissue can be controlled by nuclear or cytoplasmic genes. A student brings you a variegated spider plant. This plant appears different than the spider plants that you have seen previously which were entirely green. Design an experiment to determine the mode of inheritance of the variegated phenotype. Include in your discussion, the types of results you could see and what those results could imply regarding the mode of inheritance.

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

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 species of Epilobium (fireweed) are crossed. The female is listed first for each cross. Cross 1 - E. hirsutum x E. lauteum ===> all short progeny; Cross 2 - E. lauteum x E. hirsutum ===> all tall progeny. The progeny from cross 1 were mated as females for 20 generations to E. lauteum, and the progeny from each generation were short. Why were the backcrosses performed, and what information was gained from these backcrosses? If the progeny from cross 2 were mated as females to E. hirsutum, what would you predict the phenotype of progeny. Why?

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

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