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Rice plants have about two times as much of genes in their DNA than humans have. Then how is it possible that people have much more different cells than a rice plant has?

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    $\begingroup$ Did you have any reference about number of genes in rice plant is almost same as human being? and are these genes present as copy of few genes? or it tells about number of specific genes? OP looks something different from C-value paradox (that deals with DNA amount, not gene number). Interesting. $\endgroup$ – Always Confused Jan 19 '17 at 9:32
  • $\begingroup$ See medium.com/.../human-genome-shrinks-to-only-19-000-ge... The rice plant cell contains 30 000 genes. $\endgroup$ – descheleschilder Jan 19 '17 at 11:07
  • $\begingroup$ See quora.com/How-many-genes-are-there-in-the-genome... for the number of genes in the rice plant. So the number of genes in our cells is even smaller than it is in a rice plant! $\endgroup$ – descheleschilder Jan 19 '17 at 11:10
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Actually, rice has about twice as many genes than humans (you can check yourself on bionumbers). But who cares? It is not because two species have the same number of genes that they would look alike. Human and rice have quite different genes. Numbers in themselves do not matter.

Consider the situation where Paul has twice the number of clothes in his wardrobe than Jack, it does not necessarily mean that Paul and Jack dress up differently. Conversely, when playing poker, Paul always has the same number of cards in his hands than Jack, yet their hands may well be very different.

Generally speaking 'higher plants' tend to have way more genes than 'higher animals'. There are several hypotheses for that. Plants are more often polyploid and therefore have more neofunctionalization. Also, plants don't move. It is not impossible that they would need more genes to cope with a more varying environmental conditions.

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  • $\begingroup$ @Remib- I know the number doesn't count, but why do half the number of genes can produce so much more different cells in the human body? Can it be that the proteins in humans, coded for by the genes, are complexer than those in a rice plant? Or can it be that the amount of non-coding DNA is much bigger in humans than in rice plants? Or do more combinations of genes (and genes can be used in many different cells) produce more combinations of proteins which more different cells? $\endgroup$ – descheleschilder Jan 19 '17 at 11:37
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    $\begingroup$ @descheleschilder I would say the determining factor in "number of cell types" has mostly to do with regulation of genes. If you have two regulatory genes, just "on" and "off" could give you up to 4 cell types, but having three levels of each could give you 9. There are certainly way more than 2 regulatory genes, and they can regulate each other, to the point that there is a potential for essentially an infinite number of cell types in a human or a rice plant. The question is whether it is advantageous to develop a new cell type, not the number of available genes, for rice or humans. $\endgroup$ – Bryan Krause Jan 19 '17 at 16:33
  • $\begingroup$ @BryanKrause-In that case, why can't rice plants and humans make the different cells they need (which is much bigger in humans) with much fewer, but equal amounts of genes? If the number of regulatory cells is n, then they can give rise to $\ 2^n $ cell types. So if there are 10 of those genes the number of different cells they can give rise to has already grown to 1028 (the same genes can take part in the formation of different cells). And those regulatory genes can give rise to many new advantageous cell types, depending on the varying circumstances, by turning on or of different genes. $\endgroup$ – descheleschilder Jan 20 '17 at 0:15
  • $\begingroup$ The biggest difference though between rice plants (or other plants) and humans is that human cells contain much, much more non-coding DNA, which in my opinion is the cause of the big difference in different kinds of cells. $\endgroup$ – descheleschilder Jan 20 '17 at 0:22
  • $\begingroup$ @BryanKrause-Are regulatory genes bound to specific genes which code for a protein, or can they regulate all genes? $\endgroup$ – descheleschilder Jan 20 '17 at 0:25

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