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Study highlights variation in human mutation rates

20 June 2011
Appeared in BioNews 612

In the first direct measure of new mutation rates in humans, researchers have found that when parents pass their genes to their children an average of 60 mutations are introduced into the genetic code during the process.

The study, published in Nature Genetics online, analysed the complete genetic sequences of two families, consisting of both parents and one child, collected as part of the 1,000 Genomes Project to search for mutations that were present in children, but absent from their parents.

However, the number of mutations discovered was lower than anticipated. Professor Philip Awadalla from the University of Montreal, who co-led the study, said: 'We had previously estimated that parents would contribute an average of 100 to 200 mistakes to their child'. 

The results also suggested considerable variation in mutation rates within and between families. In one family, 92 percent of mutations were derived from the father, whereas in the other only 36 percent came from the father.

Dr Matthew Hurles from the Wellcome Trust Sanger Institute, Cambridge, UK, who also co-led the study, said: 'This is a surprise. Many people expected that in all families most mutations would come from the father, due to the additional number of times that the genome needs to be copied to make sperm, as opposed to an egg'.

Identifying new mutations was technically challenging with just one mutation occurring every 100 million nucleotides. Professor Awadalla said: 'Today, we have been able to test previous theories through new developments in experimental technologies and our analytical algorithms. This has allowed us to find these new mutations, which are like small needles in a very large haystack'.

All previous efforts to determine mutation rates have involved averaging across multiple generations or across female and male mutation rates and provided no information about variation in mutation rates between individuals.

Owing to the small number of individuals in this study, it is difficult to tell whether the variation in mutation rates between families is due to differences in mutation processes or the parents' eggs and sperm. However, these new methods can be used to look at additional families to determine the causes of variation and examine the influence of parental age and environmental exposures on mutation rates.


Genetic coding of large families to reveal risks of older parents
The Times |  13 June 2011
Our own 60 mutations
The Scientist |  16 June 2011
Variation in genome-wide mutation rates within and between human families
Nature Genetics |  12 June 2011
We are all mutants
EurekAlert (press release) |  12 June 2011
We're All Mutants: The Average Human Has 60 New Genetic Mutations
Live Science |  16 June 2011
1 November 2010 - by Owen Clark 
A four-year, £75m project to discover novel variations between human genomes has completed its pilot phase. Among the 1000 Genomes Project's initial findings are each person carries around 250 - 300 genetic mutations. Scientists have previously linked 50 - 100 of these mutations to inherited diseases...
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Around 8 per cent of human DNA is known to have come from retroviruses. This week, Nature reported scientists have discovered a second virus type can be passed between generations in our DNA...
7 September 2009 - by Alison Cranage 
Scientists based at the Wellcome Trust Sanger Institute, in Hinxton, Cambridge UK, have used ‘next generation sequencing technology' to work out the mutation rate in the human genome. The international team's findings were published in Current Biology last week....
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US researchers have discovered a gene mutation that dramatically increases the risk of leukaemia. The study, from a group based at Ohio State University in Columbus and published in the journal Cell, found a single base change in a gene called DAPK1 that leads to a seven-fold...
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