What is junk DNA ? Why is there so much of junk DNA in man ?

Question

What is junk DNA ? Why is there so much of junk DNA in man ?

Answer 1

Junk DNA makes up nearly 99percent of our genome. It is basically DNA which doesn't code for anything.

There are several theories as to why we have so much useless DNA.

Some parts of the junk DNA bear a resemblance to viral DNA, so it is thought that this may be leftovers from a virus which infected our ancestors millions of years ago and integrated itself into their DNA. Since DNA is self replicating it has been passed down ever since.

Some of the junk DNA is thought to be leftover genes which our ancestors needed but which are now obsolete (when I say ancestors I mean going right back to single cells! We've been carrying round this DNA for a long time)

And of course, some so called 'junk' DNA may actually be of use, but we simply haven't discovered what it is used for yet.

A possible advantage of all this junk DNA is that it decreases the likely-hood of a fatal mutation occurring within the coding part of our DNA. Since nearly 99percent of our DNA isn't essential for us to live, if a mutation occurs there it will not harm us.

Answer 2

Junk DNA refers to non-coding regions.  Some of it may have subtle functions (such as simply acting as a spacer).  Other sections include deactivated genes that have not been edited out of the genome.  These segments show how random changes and natural selection are slow editors.