What this mom eats
can affect herchild's DNA.
Scientists have wanted to investigate the effects of mom's diet on her children's DNA for a long time. But it obviously wouldn't be right to do tests with pregnant women. So scientists needed another way to test their ideas.
What they used were people who were born during a famine. Famine means time where people didn't have enough food.
In 1944-1945 there was a famine in the Netherlands. Scientists decided to look at the DNA of people who were conceived and/or born during the famine. They compared these people's DNA to their brothers and sisters born during normal times.
In this study scientists decided to look at a gene in these people's DNA called IGF2. This gene is involved in human growth and development. So if the famine affected this gene, then it could have long-term effects on the health of the baby as it grew into an adult.
The scientists studied the following two groups of people 60 years after they were born:
- People whose moms were exposed to the famine during the very early part of pregnancy.
- People whose moms were exposed to the famine during the late part of pregnancy.
The scientists found the IGF2 gene of people whose moms were exposed to famine during early pregnancy were different than their siblings. But those exposed to famine during late pregnancy had no changes to their DNA.
This means that mom's diet while pregnant can affect her children's DNA. But only if the famine is during the early days of pregnancy. And those DNA changes can stay around for at least 60 years.
Genes and DNA structure
So what exactly are these changes? And why did it only happen in those whose mothers were exposed to famine early in pregnancy? To answer these questions we first have to understand the basics of genes and DNA structure.
A gene is a piece of DNA. DNA is made up of four bases called A, T, G and C. Cells read this DNA and, following its instructions, make a protein. Proteins are molecules that are involved in almost everything a cell does.
The IGF2 gene has the instructions for the Insulin-like Growth Factor 2 protein. This protein promotes growth and division of cells. And it is most active during fetal development.
The changes the scientists studied in the IGF2 gene are not in its bases. Instead they looked at DNA changes that affect how often a gene gets read. And so, how much protein gets made.
A gene doesn't only have the instructions for making a certain protein. It also includes information about when and how much protein to make.
This is because every cell doesn't make the same amount of every protein. That's why our cells are so different even though they have the same DNA.
Cells control which and how much protein gets made by turning genes on and off. The human body has over 6 feet of DNA packed into each cell. So in order for genes to get turned on the compact DNA needs to be loosened up so the cell can read the DNA sequence.
DNA Methylation Turns Genes On or Off
One way in which cells can loosen or tighten DNA to turn genes on or off is by something called epigenetics
. It sounds complicated but breaking the word apart shows it's actually very simple.
DNA methylation turns
genes on and off.
"Epi" comes from Greek and means "on" or "over". And genetics refers to a gene. So "epigenetic" literally means "on a gene.
Methylation is an epigenetic way to affect a gene (see picture at right). Methylation refers to a methyl group placed on or taken off a gene.
A methyl is a very small chemical group made up of one carbon atom and three hydrogen atoms. Usually more methylation means a gene is turned off and less methylation means a gene is turned on.
Methylation is one example of how genes can be directly affected by the environment. The environment can actually change how many methyl groups are placed on the DNA. This then leads to genes being turned on or off.
For example, previous studies with animals have shown that a mother's diet during pregnancy can affect how methylated her children's DNA is. One study altered the diet of pregnant mice. Depending on what the mom ate the baby pups came out either yellow or brown
. This was because of differences in methylation on certain genes.
What's more interesting is that the yellow pups grew up to have yellow babies. And the brown mice grew up to have brown babies. That means the differences in DNA methylation stayed with the pups their whole lives. And even into their babies lives!
So the scientists in this famine study set out to find out if something similar was happening in people. They indeed found that famine affected the methylation of the IGF2 gene. But only if the famine happened early in pregnancy.