Question

Chlamydomonas reinhardtii is a unicellular algae that contains a single chloroplast, each with about 50 – 100 genomes and multiple mitochondrial organelles also with multiple genomes. Although C. reinhardtii exists mainly as a haploid organism, occasionally two cells will fuse to form a diploid cell which immediately undergoes meiosis to form four haploid progeny. The cells that fuse must be of opposite mating type, mt+ and mtInheritance of the plastid genome is uniparental mt+, whereas inheritance of the mitochondrial genome is uniparental mt- . Mutant alleles which confer resistance to antibiotics have been identified in C. reinhardtii and these are quite often variants of genes found in organellar genomes. For instance, a mutant allele conferring resistance to streptomycin (strR) maps to the chloroplast genome and a mutant allele conferring resistance to hygromycin (hygR) maps to the mitochondrial genome (wild-type sensitive alleles are designated with a superscript S). Suppose you mate an mt+ strR hygS strain of the algae with an mt- strS hygR strain. What will be the most likely phenotype of a progeny cell?

A. streptomycin resistant,hygromycin resistant B. streptomycin resistant,hygromycin sensitive C. streptomycin sensitive,hygromycin resistant D. streptomycin sensitive, hygromycin sensitive

Answer 1