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Cryptic sentence - (Aug/27/2012 )

"Unlike most commonly studied eukaryotes, Chlamydomonas reinhardtii is haploid, suggesting the efficacy of natural selection in this organism may be high".

(Taken from Jang and Emmerich, PLoS ONE, 2012).

Who would like to explain this declaration to me as if I were a (very smart) eight-year-old?


As defined in the wiktionary: haploid = Of a cell having a single set of unpaired chromosomes; vs diploid which has a pair of each chromosome i.e. if you have 2 chromosomes of each, if you get a mutation that is deleterious in one chromosome it happens that this condenses (epigenetical deactivation) while the other chromosome becomes activated and the gene is used from the active/healthy chromosome. If an organism is haploid, it doesn't have a spare chromosome so if a deleterious mutation happens, it is more or less screwed --> natural selection.

Think in terms of X-linked diseases being abundant in males. Males have one X and one Y; if the X chromosome is screwed, he doesn't have a spare one so disease occurs; while in females: easy peasy, just activate the other X chromosome and deactivate the sick one. In females, to get a x-linked disease, both X's must be affected, which is unlikely.



Thanks, great answer!

I would've figured it out myself if it weren't for the rather confusing phrasing, in my humble opinion, "high efficacy of natural selection". I've been reading lately several opinions by elderly, senior scientists, who publicly complain about the increasing "unreadability" of articles published nowadays. I wonder if this is what they meant. Or maybe I'm just dumb.


You/nature can not afford to due bad to haploid genome organism, as you play odd and it dies. Afterall who then will listen to Darwinian survival of fittest? so that may logic behind high efficacy of natural selection in Chlamydomonas.