Describe the adaptive (evolutionary) significance of organizing genes into chromosomes.?

Answer 1

Hmm ... I can't understand why Dan calls this " the single most controversal idea of the 21st century." It's a simple (and interesting question), and not that controversial.

The question is, what advantage is served by having genes grouped into chromosomes, instead of floating around as thousands of loose pieces of DNA or RNA?

The answer is that is dramatically simplifies the process of dividing the genes up during cell reproduction so that each cell gets a full copy of the genes. Without chromosomes, cell reproduction would require some method to identify and replicate each and every one of those thousands of genes. In other words, chromosomes is what allows inheritance, not matter how much genetic material (genes) the organism has.

DNA is extremely robust, and can form in *extremely* long strands (either circular or linear). Thus it is just as easy for many genes to be strung together in the same strand (a chromosome) than it is for each gene to be a separate strand of DNA.

So once organisms moved from using RNA to DNA as the molecule of choice for storing genes, there is absolutely no reason to store each gene as a separate piece of DNA.

So the way evolution produces longer and longer chromosomes is just a side effect of it producing more and more genes. The mechanisms of cell division (mitosis and meiosis) work quite well with one or two, or dozens, or even one or two hundred separate pieces of genetic material (chromosomes) in some species ... but any more than that and the repllication breaks down ... so such organisms don't occur.

A second reason is more complex, but equally interesting. By storing multiple genes on the same strand of DNA, the genetic code now has access to far more complex methods of storing information. One gene can serve no other purpose than to turn other genes, or entire combinations of genes, on or off. This gives the bearer all sorts of opportunities for new genetic "experiments". In other words, instead of a mutation affecting only one protein at a time (one gene at a time), a single mutation can affect entire collections of proteins, or even entire structures, in the organism. In short, it dramatically increases the potential for radically new approaches to survival. Most of these "new approaches" fail dismally, with lethal results, and don't last very long. But the occasional ones that do succeed ... in the sense of providing some advantage, no matter how small ... will propagate into the population, and affect its evolution.

It is the grouping of genes into chromosomes that allows higher-level of complexity.

Answer 2

Wow talk about the single most controversal idea of the 21st century... Honestly though, this is the big mystery of life. This is a question that even the top genetisists and biologists cant answer for sure. The most logical answer is however, life is simple, and life found a simple way to determine how it is shaped. Genes are the blueprints for life. It is our DNA that determines almost every feature of our physical and chemical makeup (the other small percentage comes from environmental factors that occur in our lifetime). There is a theory that DNA/ Chromosomes formed before life itself, during the adolesant stages of earths life. Simple molecules formed to create the first "DNA" which in turn began to create more of itself, acting as a catalyst in its own replication. Overtime, the molecules change and grow and essentially evolved become more complex and over millions of years became the first single celled organisms...