[thedoc]

Hi Naked Scientists
My question is- how do mutations occur in human beings?




Asked by Rashi Rustagi


                                        Visit the webpage for the podcast in which this question is answered.

 

[CliffordK]

DNA Reproduction is not exact. 
The cells have error correction routines to improve the accuracy, but end up with an error rate of 1 transcription error in 10^-9 to 10^-11 nucleotides.

The human genome has about 2.9 x 10⁹ nucleotides.

So, there is somewhere between a couple of uncorrected errors per cell division to an error in every few hundred cell divisions.

The errors can either occur in the gametes, leading to a new mutation that can be passed on, or occur in the normal cell division in the human body, sometimes leading to developmental problems, or to cancers.

Some of the DNA errors are insignificant.  Others may be be be damaging, but since cells are diploid, they may not cause a problem. 

If a baby's mother and father each have a few hundred "mutated" genes, both new mutations, and those from previous generations, then the baby will inherit an imperfect set of genes. 

If the parents unrelated, the likelihood that these mutated genes will be the same would be relatively rare, and the infant will receive one good copy of every gene.  However, if the parents are closely related, then there is a much greater possibility of sharing the same mutations, and getting two mutated copies of genes.

[CZARCAR]

DNA "switches" that control the DNA  & are 80% of the DNA...PBS

[Devilmunkey]

Yes copying errors are the main source of mutations in DNA and many are neither advantageous (in an evolutionary sense) or detrimental, there are also mutations causesd by environmental influences such as exposure to certain types of radiation. This can cause direct damage to DNA, resulting in mutations (the poor fruitfly has been at the brunt of research into this). Sadly these mutations are usually relatively mundane in their expression: no bone claws or healing factor…