From the thread "Simple arithmetic provides a testable challenge to evolution"
Post of the Month: December 2001
by Prof Weird
Subject: Re: Simple arithmetic provides a testable challenge to evolution Newsgroups: talk.origins Date: December 6, 2001 Author: Prof Weird Message-ID: email@example.com
If the genes are identical, what other conclusion could you draw other than duplication?
There is some evidence for two genome wide duplications (ALL genes doubled up) since the jawless fish, but I believe these articles may be more in line with what you want :
"Spontaneous tandem sequence duplications reverse the thermal stability of carboxy-terminal modified 3-isopropylmalate dehydrogenase", S Akanuma, A Yamagishi, N Tanaka, T Oshimi, Journal of Bacteriology Nov 1996 #178, pg 6300-6304
They removed 22 bp from the end of leuB gene of a thermophilic bacterium (can grow without leucine at 65 degrees, but not at 75 degrees).
3 spontaneous mutations arose that could grow without leucine at 75 degrees - they were all DUPLICATIONS of DNA.
"Tandem sequence duplications functionally complement deletions in the D1 protein of photosystem II", H Kless and W Vermaas, Journal of Biological Chemistry, 270 #28 (1995), pg 16536-16541
Deleted sequences from a cyanobacterium's D1 protein - could no longer perform glycosynthesis (requires glucose for growth).
In one line (dYNIV - deletion of 4 amino acids) 3 mutants arose - from duplications of DNA near the deletion site. Some were frameshifted, but the addition of the new nucleotides enabled the cells to make glucose again.
In another line (dNN - deletion of 2 amino acids in a different location) 3 mutants arose - again by duplications of DNA in the area. 2 of the 3 were frameshifts (relative to the parental sequence), but they did permit the cells to make glucose again.
"Accelerated regulatory gene evolution in an adaptive radiation", M Barriu, RH Robichaux, MD Purugganam, Proceedings of the National Academy of Sciences (98) #18, pg 10208-10213
The Hawaiian silversword alliance are a collection of 30 species in 3 genera found in Hawaii - analysis of their DNA and enzymes shows that they all arose from a FUSION and duplication of 2 different plant genomes - ancestors were most likely Anisocarpus scabridus and Carlquisia muirii (North American tarweeds).
The Hawaiian silversword alliance are tetraploids, whereas the parental lines are diploids. This is common in plants - although a hybrid between two different but related species is usually sterile (chromosomes can't pair up properly - [1A + 1B] chromosome set, where A is from one parent, B is from the other, and when make gametes, divide A and B by half but MUST be an integer).
Occassionally in a growing shoot, the chromosomes double [2A + 2B] but no cell division occurs. This hybrid is NOW SELF-FERTILE, AND A NEW SPECIES. Gametes are [A + B] - can produce progeny from self-fertilization, but NOT with A or B parental stocks.
Most agricultural plants today are tetraploid or octoploid - makes them bigger. Strawberries, IIRC, are 16N or so (from crossing two closely related species then doubling chromosome numbers to render them fertile, done several times).
Home Page | Browse | Search | Feedback | Links