5 ms·

Not stupid at all. If you're interested in that, I'd look up "Whole Genome Duplications". For instance, corn underwent a WGD about 7 million years ago (IIRC,

Not stupid at all. If you're interested in that, I'd look up "Whole Genome Duplications". For instance, corn underwent a WGD about 7 million years ago (IIRC, the number might be off), and we can identify an 'a' and 'b' genome. After these events, most of the duplicated genes will be lost, either through purging selection or drift. However, some will stick around and take on new subset functions (see nkrumm reply). If you really want to get into the weeds on this, there are many metrics that could, in theory, affect the 'evolvability' of a genome. Higher transposon (or any sort of repetitive element) content can lead to large-scale shuffling of genome structure, such as inversions, duplications, etc. The ecological success of the grass family, for instance, may have it's roots in genome structure. Now, there's not a whole lot we can say about this because it's not something we have a really good grasp of. It's mostly some hypotheses that are quite difficult to test, but this is some of the most interesting genomic research going on, in my opinion. All of this is quite difficult to understand, however, as it really depends on epigenetic mechanisms like chromatin state, dicers, RISC, and all that. Figure that out, and you'll realize there's no 'junk' DNA, just various non-coding sequence that's part of this larger-scale genome evolution.

quotemstr 9y ago
Why is it that plants are so much better than animals at tolerating chromosomal shenanigans? Plants can be highly polyploid, get chromes swapped out, randomly get duplicates, etc., and not seem to suffer massive problems. In a human, you duplicate one chromosome, and you get a very buggy phenotype.
- a_bonobo 9y ago
  This has, as usual, several reasons :) One reason is the absence of sex chromosomes in plants. If humans get a duplicated sex chromosomes things go completely haywire. Another reason is that due to so many WGDs, plants have ample gene copies, so the copies can freely mutate around or even break, there's always a backup. Not all of these shenanigans work out, in plants this has the wonderful name 'genomic shock'. In wheat there's a candidate gene (Ph-1) which seems to somehow stabilise these instabilities between chromosome copies. In other species people have been trying for a few years to make polyploids but have been failing because there is no stability mechanism - for example, there are only few papers where people managed to make a Brassica hexaploid, these hexaploids are usually very unstable and have problems generating offspring (see for example http://www.cropj.com/malek_7_9_2013_1375_1382.pdf http://www.cropj.com/malek_7_9_2013_1375_1382.pdf )

quotemstr 9y ago

Why is it that plants are so much better than animals at tolerating chromosomal shenanigans? Plants can be highly polyploid, get chromes swapped out, randomly get duplicates, etc., and not seem to suffer massive problems. In a human, you duplicate one chromosome, and you get a very buggy phenotype.

a_bonobo 9y ago
This has, as usual, several reasons :) One reason is the absence of sex chromosomes in plants. If humans get a duplicated sex chromosomes things go completely haywire. Another reason is that due to so many WGDs, plants have ample gene copies, so the copies can freely mutate around or even break, there's always a backup. Not all of these shenanigans work out, in plants this has the wonderful name 'genomic shock'. In wheat there's a candidate gene (Ph-1) which seems to somehow stabilise these instabilities between chromosome copies. In other species people have been trying for a few years to make polyploids but have been failing because there is no stability mechanism - for example, there are only few papers where people managed to make a Brassica hexaploid, these hexaploids are usually very unstable and have problems generating offspring (see for example http://www.cropj.com/malek_7_9_2013_1375_1382.pdf http://www.cropj.com/malek_7_9_2013_1375_1382.pdf )