Related Experiment Video
Updated: Aug 8, 2026

Mating and Tetrad Separation of Chlamydomonas reinhardtii for Genetic Analysis
Published on: August 12, 2009
Mating type in Chlamydomonas is specified by mid, the minus-dominance gene
1Department of Biology, Washington University, St. Louis, Missouri 63130, USA. ferris@wustlb.wustl.edu
Abstract:
Diploid cells of Chlamydomonas reinhardtii that are heterozygous at the mating-type locus (mt+/mt-) differentiate as minus gametes, a phenomenon known as minus dominance. We report the cloning and characterization of a gene that is necessary and sufficient to exert this minus dominance over the plus differentiation program. The gene, called mid, is located in the rearranged (R) domain of the mt- locus, and has duplicated and transposed to an autosome in a laboratory strain. The imp11 mt- mutant, which differentiates as a fusion-incompetent plus gamete, carries a point mutation in mid. Like the fus1 gene in the mt+ locus, mid displays low codon bias compared with other nuclear genes. The mid sequence carries a putative leucine zipper motif, suggesting that it functions as a transcription factor to switch on the minus program and switch off the plus program of gametic differentiation. This is the first sex-determination gene to be characterized in a green organism.
Related Concept Videos
Monohybrid Crosses
Test Cross
Chi-square Analysis
The chi-square test was developed by Pearson in 1990.
The first step of performing a Chi-square analysis is to establish a null hypothesis, which assumes that there is no real...
Incomplete Dominance
The Ratio of X Chromosome to Autosomes
Normal male Drosophila has a ratio of one X chromosome to two sets of autosomes. In contrast, normal female Drosophila...
Dosage Compensation
In addition to sexual development, the X chromosome has genes involved in autosomal functions such as brain development and the immune system. Therefore, males and females with distinct numbers of X chromosomes will have...

