For our new visitors – basic genetics!
To help keep you up to date with the social scene chatting up this new area, we explain below some common terms that you are likely to encounter.
First off, any trait or characteristic, behavior, or disease arises from two contributing factors –some from environmental exposure and some that you inherit from your parents, their parents, and so forth. Every single cell in your body originates from a single fertilized egg thatcarries a blueprint for what you inherit.
Inside each of you and each of your cells, a molecule called DNA carries your inherited blueprint. DNA is made up of 4 different building blocks called the A, T, G, and C bases. These bases are glued together like pearls on a string to form a very long DNA strand. Each strand matches up and binds to a complementary strand, like Velcroforming the double helix as seen above.
Two of these DNA strands bind together with special proteins forming the Chromosomes that live in the nucleus of the cell as seen above. On each DNA strand, the sequence of the A, T, G, and C bases, like the “0”s and “1” that make up all computer software, carry the inheritance or genetic information.
Some, but not all, of these DNA sequences are units called Genes thatlike computer code, essentially program the active functions in cells. A molecular machine translates the DNA sequence of each gene into a unique Protein. So, proteins also have a sequence, but this time it is a sequence from 20 different types of amino acids. Some of the proteins that you may have heard of are Hemoglobin,which carries oxygen to all your cells, and Insulin, a hormone that tells your cells when to eat sugar. Tens of thousands of proteins work together to carry out the business of living. So proteins are not just for eating! Eye color and blood type are just two of many thousands of outcomes that arise from this network of proteins.
In each cell of your body, you have 23strands of DNA from each parent that make up your 23 chromosomes. Thus, you have two copies of each gene, one from each parent – yes mom and dad’s copies are very similar, but most often do have some changes and each slightly different gene is called an Allele. Each parent contributes one allele, thatdiffer from each other with minor sequence changes.
Each allele change is called a genetic Variant. These sequence changes can alter how a gene works! Some alleles are Dominant meaning the allele from one parent over-rides the gene from the other parent, and the subordinate allele is termed Recessive. Consider if a father has red hair and mother has brown hair and all the children have brown hair, the allele inherited from the mother for brown hair is dominant over the allele for red hair from the father. The father may have had two alleles for red hair and mother may have had two alleles for brown hair; in both cases the parents’ alleles for this gene are Homozygous. When a brown haired child has a brown haired allele from mom and a red haired allele from dad this gene is called Heterozygous.
Most often inheritance is not just from a single gene, but turns out to be much more complex where many genes contribute to any feature or trait. This is called Polygenic. We are still in our infancy in understanding these interactions, especially when it comes to the impact, of our diets on our daily lives!
Now to the nitty gritty of how this all relates to a Food Genes And Me nutritional report.
Scientists compare a group of people that eat a particular food with a control population that does not. They look for variants that are found much more often in the test population than the control population. When this is done scanning the entire DNA it is called a Genome Wide Association Study (GWAS). This is where statistics becomes important to determine what is a valid association, and what is just background noise that cannot later be reproduced consistently.
Remember when fat-free was the craze and then fats later became good for you? Rigorous scientific studies - like those GWAS studies screened by Food Genes And Me - are increasingly teasing out the impact of these single changes. (We saw a dramatic impact of a variant in last week’s blog on the FTO gene!). However, for identifying the best diets, Food Genes And Me is focused on defining the polygenic basis of nutrigenetics. That is why we ask you to fill out our survey, so that we can discover new variants together.
Stay tuned for a follow-up on basic genetic terminology in a future post!
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Comments
I never knew what GWAS meant - thank you
By : Jamie On January 2nd 2019Good post and I would like to learn more, especially SNPs and what the 'rs' numbers mean.
Replied by : Martin Schiller On January 8th 2019