Uniparental Inheritance in Chlamydomonas Reinhardi

	Genetics Home
Cytoplasmic or Extranuclear Inheritance Cytoplasmic or Extranuclear Inheritance Comparison of Extra Nuclear and Nuclear Genetic Systems Extra Nuclear Inheritance in Eukaryotes Extra Nuclear Inheritance by Cellular Organelles Extra Nuclear Inheritance by Endosymbionts

Uniparental Inheritance in Chlamydomonas Reinhardi

Uniparental Inheritance in Chlamydomonas Reinhardi
R. Sager (1954, 1970) and N. Gilham (1968) have reported various case of extra chromosomal inheritance in green alga Chlamydomonas reinhardi which reproduces asexually as well as sexually. During sexual reproduction, two cells of opposite sexes fuse to form zygote. Sex is determined by a single chromosomal gene, two of the four daughter cells form female progeny, while the other two give rise to male progeny. Although both of the sexes contribute equally to the zygote, there is primarily maternal inheritance of certain traits that are due to cytoplasmic factors (DNA molecules of chloroplasts and mitochondria )
The uniting gametes of the single celled alga, Chlamydomonas reinhardi are morphologically indistinguishable.

One strain of the alga which is streptomycin resistant (Sr) and of the "plus" mating type (mt+) is crossed to a cell of "negative" mating type (mt-) which is streptomycin sensitive (SS). All the progenies are resistant but the nuclear genes for mating type segregate as expected: ½ mt+; ½ mt-. The reciprocal cross, SSmt+ X Srmt-, again shows the expected segreegation for mating type, but all progenies are sensitive. Repeated back crosses of Srmt+ to SSmt- fail to show segmentation for resistant. It appears as though the plasmagenes of mt- strain are lost ill a zygote of mt+. The mechanism which inactivates the plasmagenes of mt- in the zygote is unknown.

	Genetics Home
Uniparental Inheritancein Chlamydomonas Reinhardi Extra Nuclear Inheritance in Episomes Extra Nuclear Inheritance in Plasmids Kinds of Plasmids Inheritance of Performed Structures

Home | Site map | Submit Article | Directory | Search