From: Andy Soos, ENN
Published August 24, 2012 11:42 AM
Paternal Mutations
Mutation is simply defined as "random changes in genetic material".
Without mutations and there would be very little change in species or
evolution. Humans inherit more than three times as many mutations from
their fathers as from their mothers, and mutation rates increase with
the father’s age but not the mother’s, researchers have recently found
in the largest study of human genetic mutations to date. The study,
based on the DNA of around 85,000 Icelanders, also calculates the rate
of human mutation at high resolution, providing estimates of when human
ancestors diverged from nonhuman primates. It is one of two papers
published this week by the journal Nature Genetics as well as one
published at Nature that shed dramatic new light on human evolution.
“Most mutations come from dad,”� said David Reich, professor of
genetics at Harvard Medical School and a co-leader of the study. In
addition to finding 3.3 paternal germline mutations for each maternal
mutation, the study also found that the mutation rate in fathers doubles
from age 20 to 58 but that there is no association with age in mothers.
The researchers used these empirical observations to build a model that
was applied to individuals allowing a way to estimate key parameters of
evolution without calibration to the fossil record. It was inhered that
the sequence mutation rate is 1.4—2.3 × 10−8 mutations per base pair per
generation and that human-chimpanzee speciation occurred 3.7—6.6 million
years ago.
Although recent human evolution is difficult to observe directly, some
of its impact can be inferred by studying the human genome. In recent
years, genetic studies have uncovered many examples where recent
evolution has left a distinctive signature on the human genome. The
clearest footprints of evolution have been seen in regions of DNA
surrounding mutations that occurred fairly recently (typically in the
last several thousand years) and confer an advantageous trait, such as
resistance to malaria.
Hirschhorn’s team observed, for the first time in humans, a different
signature of recent evolution: widespread small but consistent changes
at many different places in the genome, all affecting the same trait,
adult height.
"This paper offers the first proof and clear example of a new kind of
human evolution for a specific trait," said Hirschhorn, who is also a
senior associate member of the Broad Institute. "We provide a
demonstration of how humans have been able to adapt rapidly without
needing to wait for new mutations to happen, by drawing instead on the
existing genetic diversity within the human population."
Average heights can differ between populations, even populations that
are genetically very similar, which suggests that human height might
have been evolving differently across these populations. Hirschhorn’s
team studied variants in the genome that are known to have small but
consistent effects on height.
The researchers discovered that, in northern Europe, the tall versions
of these variants are consistently a little more common than they are in
southern Europe. The combined effects of the tall versions being more
common can partly explain why northern Europeans are on average taller
than southern Europeans. The researchers then showed that these slight
differences have arisen as a result of evolution acting at many
variants, and acting differently in northern than in southern Europe.
For further information see
Mutations or
Article.
Figure image by James Sun/Harvard Medical School
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