How Quickly Does Human DNA Mutate? 73contained in 20 chromosome pairs and current results suggest that it is about
2.7 billion base pairs in size, or about 15% smaller than the human genome. If
one takes a conservative estimation of the mutation rate of 5×10−7 mutations/
cell/generation, the generation of 3.7×10^13 cells would cause several log higher
mutations in a man than in a mouse. Similar logic can be applied to the human
versus mouse brain. But, this is a very simplistic approach; a human brain is far
more complex than a mouse brain and one cannot duplicate the findings in a
mouse of a human by any means. This is not to say that the animal models are
not useful in making broader implications but in the case of autism research a
rodent or any small animal model is highly inadequate. If should also be noted
that an adult animal body is constantly accumulating mutations while the cells
are dividing and in a human body DNA replication happens across 70 years
whereas in a mouse it lasts only for 3 years. Therefore, the degree of somatic
cell mutations would be hundreds of times higher in a human than in in a
mouse.
How Quickly Does Human DNA Mutate?
Every time human DNA is passed from one generation to the next it accumu-
lates 100–200 new mutations, according to a DNA‐sequencing analysis of the
Y chromosome. This number – the first direct measurement of the human
mutation rate – is equivalent to one mutation in every 30 million base pairs,
and matches previous estimates from species comparisons and rare disease
screens [65].
The British–Chinese research team that developed the estimate sequenced
10 million base pairs on the Y chromosome from two men living in rural China
who were distant relatives. These men had inherited the same ancestral male‐
only chromosome from a common relative who was born more than 200 years
ago [66,67]. Over the subsequent 13 generations, this Y chromosome was
passed faithfully from father to son, albeit with rare DNA copying mistakes.
The researchers cultured cells isolated from the two men, and by utilizing
next‐generation sequencing methods discovered 23 candidate mutations 12 of
which were further validated by using traditional sequencing. Eight out of 12
of these mutations had arisen in their cell‐culturing process. Therefore, only
4 genuine, heritable mutations were left. Extrapolating that result to the whole
genome gives a mutation rate of around one in 30 million base pairs. This
direct measurement of the mutation rate can be used to infer events in our
evolutionary past, such as when humans first migrated out of Africa, more
accurately than previous methods. Most of the Y chromosome does not mix
with any other chromosomes, which makes estimating its mutation rate easier.
But the mutation rate might be somewhat different on other chromosomes.
Also, there is a gender bias in mutations towards the male.