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INTERACTIVE DNA DISCOVERY
DNA provides the blueprint for all living things.
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Your body is made of trillions of building blocks called cells, the same way a house is built from bricks. There are many types of cells: brain cells, heart cells, skin cells, and more!
Almost every cell has DNA, or deoxyribonucleic acid. Most cells have the same DNA but each type of cell "reads" different parts of it. DNA tells the cell how to develop and function.
Most DNA is stored inside a compartment in the cell called the nucleus, similar to an egg yolk inside an egg. There is also some DNA housed outside the nucleus, in structures called mitochondria. All of your DNA together is called your genome.
Altogether, the DNA inside a single human cell is about six feet long. In order to fit inside a cell, DNA is coiled up tightly and divided into sections called chromosomes.
You inherit one set of 23 chromosomes from your dad and one set of 23 chromosomes from your mom — for a total of 23 pairs of chromosomes.
Organisms vary greatly in their number of chromosomes. For example, cucumbers have 7 pairs, chimpanzees have 24 pairs, and giant salamanders have 30 pairs.
The 23rd pair of chromosomes, called the sex chromosomes, are different from the other 22 pairs. There are two kinds of sex chromosomes, the X chromosome and the Y chromosome. Having two X chromosomes (XX) makes you genetically female. Having an X chromosome and a Y chromosome (XY) makes you genetically male.
How does that work? You inherited one of your mom's two X chromosomes. And you inherited either your dad's X or Y chromosome. If you inherited his X chromosome, then you have XX chromosomes and are genetically female. If you inherited his Y chromosome, then you have XY chromosomes and are genetically male. Sometimes, a person’s genetic sex, the sex assigned at birth, and/or the deeply-held sense of gender are not all the same.
If all your DNA (your genome) is a cookbook, then your genes are the recipes. Genes are sections of DNA that contain instructions for making proteins and RNAs. Human DNA contains around 20,000 protein-coding genes and likely thousands of RNA genes.
Proteins do most of the work in the cell. They carry out tasks necessary for building and maintaining the cell, like transporting oxygen, detecting invading bacteria, forming the structure of your hair, and countless other jobs.
RNAs are molecules similar to DNA. They help build proteins and regulate when and where different proteins are made.
The process of building a protein using the DNA code happens in two steps called transcription and translation. During transcription, the cell creates a temporary copy of the gene called messenger RNA. During translation (as shown), the cell follows the gene instructions contained in the messenger RNA to link together a chain of small molecules, called amino acids.
There are 20 different amino acids, each with unique properties. The order in which they are combined determines the properties of the protein. A vast array of proteins are possible, and they can move, interact with other proteins, and change shape to do their jobs.
Only a small part of your DNA contains the genes that code for proteins.
Some DNA contains regulatory elements, which are stretches of DNA that regulate how and when the cell should "read" different genes.
Some DNA codes for different kinds of RNAs that play a variety of roles in the cell. And some DNA has no known function.
DNA is shaped like a long twisted ladder, or a double helix. Each rung of the ladder is made of two molecules called bases, forming a base pair. There are four types of DNA bases: adenine (A), thymine (T), guanine (G), and cytosine (C). The bases always pair up according to these rules:
The two vertical sides of the ladder are made of alternating sugar (S) and phosphate (P) molecules. The combination of a sugar, a phosphate, and a base is called a nucleotide.
These nucleotides are connected together into long DNA sequences. We have about 3 billion nucleotides in our genome.
It's been estimated that our DNA sequences are about 99.5% identical. But there are parts of our DNA that vary from person to person.
These DNA differences are called genetic variants. Some genetic variants have no effect. Others influence traits and health — like your hair color, weight, and risk of certain diseases.
A genetic variant can influence your traits by changing how a protein gets built, which changes how that protein does its job. For example, certain genetic variants cause proteins inside the hair follicles to produce more red pigment molecules — leading to red hair.
The most common type of genetic variant is when people have different base pairs (DNA letters) at one particular place in their DNA. For example, at the same place in a gene, one person might have an A (adenine), while another person has a C (cytosine). These differences are called single nucleotide polymorphisms, or SNPs (pronounced “snips”).
Other examples of genetic variants include:
You inherit genetic variants from your parents, but new variants can also appear in your DNA. They can be the result of damage to DNA, or a side effect of normal cell processes like making new copies of DNA.
Usually new genetic variants are corrected by "DNA repair" proteins in the cell. Most uncorrected DNA segments are not harmful. In fact, they typically have no effect at all.
Occasionally, a new genetic variant can lead to a new trait — for example, by changing the function of the protein that that gene codes for.
If a new genetic variant results in a new trait that helps living things survive and reproduce, that variant and trait can become more common over time.
For example, research suggests that most ancient humans were lactose intolerant, meaning they could not digest the sugar lactose in dairy products like cheese, milk, and yogurt, as they grew older.
But several thousands years ago, in some regions of Europe and Africa, humans started domesticating cows, goats, and sheep and depended on the animals' milk for nutrients. New genetic variants appeared by chance that gave these groups of people the ability to digest dairy into adulthood. This helped them adjust to their new diet, and these genetic variants became more common.
Oftentimes people think that a single gene or genetic variant determines a trait. Sometimes that's true, but it's usually more complicated than that. Take eye color, for example: many genes play a role in creating the color pigments in the eye, and genetic variants in any of them can affect your eye color.
This can also be true for diseases. For example, dozens of common genetic variants are linked to developing type 2 diabetes. Alone, each of them only have a tiny impact on risk of developing type 2 diabetes, but together they can add up to an overall higher risk.
Genetics can tell you a lot about yourself, but it isn't the only factor to consider.
For almost all human traits, factors like lifestyle and environment play a role along with genetics. Your height, for example, depends on the effects of many genetic variants as well as environmental and lifestyle factors like your diet.
This means you can have genetic variants that are linked to being tall, but if you have poor nutrition growing up, you may end up being shorter than other people with those same genetic variants.
Even when we know multiple factors influence the development of a trait (like genetics, lifestyle, and environment), it's impossible to know for sure how things will turn out for a given person. That's why genetic associations are stated in terms of likelihood or risk.
For example, in one study, researchers found that 30% of male participants with certain genetic variants experienced complete hair loss or balding, while 70% did not.
This means that men with those same genetic variants have about a 30% risk of experiencing complete balding. You could also say that they have a 70% chance of not experiencing complete balding.
In the 1990s and early 2000s, scientists mapped the complete sequence of the human genome for the first time. Those data helped scientists learn about how thousands of genes function in the body, and how certain genetic variants impact human traits, health, and disease.
Scientists can "read" DNA with techniques called "sequencing" and "genotyping."
Sequencing determines the exact DNA letters and their order in a stretch of DNA.
Genotyping looks at DNA letters of interest at specific locations. Genotyping is the technology that 23andMe uses.
Discovering more about your genetics can be one of the most exciting ways to learn more about yourself. Now that you have learned these basic DNA concepts, you're well on your way to exploring even more about yourself through your DNA!
* The 23andMe PGS test includes health predisposition and carrier status reports. Health predisposition reports include both reports that meet FDA requirements for genetic health risks and reports which are based on 23andMe research and have not been reviewed by the FDA. The test uses qualitative genotyping to detect select clinically relevant variants in the genomic DNA of adults from saliva for the purpose of reporting and interpreting genetic health risks and reporting carrier status. It is not intended to diagnose any disease. Your ethnicity may affect the relevance of each report and how your genetic health risk results are interpreted. Each genetic health risk report describes if a person has variants associated with a higher risk of developing a disease, but does not describe a person's overall risk of developing the disease. The test is not intended to tell you anything about your current state of health, or to be used to make medical decisions, including whether or not you should take a medication, how much of a medication you should take, or determine any treatment. Our carrier status reports can be used to determine carrier status, but cannot determine if you have two copies of any genetic variant. These carrier reports are not intended to tell you anything about your risk for developing a disease in the future, the health of your fetus, or your newborn child's risk of developing a particular disease later in life. For certain conditions, we provide a single report that includes information on both carrier status and genetic health risk. Warnings & Limitations: The 23andMe PGS Genetic Health Risk Report for BRCA1/BRCA2 (Selected Variants) is indicated for reporting of 44 variants in the BRCA1 and BRCA2 genes. The report describes if a person's genetic result is associated with an increased risk of developing breast cancer and ovarian cancer and may be associated with an increased risk for prostate cancer, pancreatic cancer, and potentially other cancers. The variants included in this report do not represent the majority of the BRCA1/BRCA2 variants in people of most ethnicities. This report does not include variants in other genes linked to hereditary cancers and the absence of variants included in this report does not rule out the presence of other genetic variants that may impact cancer risk. This report is for over-the-counter use by adults over the age of 18, and provides genetic information to inform discussions with a healthcare professional. The PGS test is not a substitute for visits to a healthcare professional for recommended screenings or appropriate follow-up. Results should be confirmed in a clinical setting before taking any medical action. For important information and limitations regarding each genetic health risk and carrier status report, visit 23andme.com/test-info/
**23andMe PGS Pharmacogenetics reports: The 23andMe test uses qualitative genotyping to detect 3 variants in the CYP2C19 gene, 2 variants in the DPYD gene and 1 variant in the SLCO1B1 gene in the genomic DNA of adults from saliva for the purpose of reporting and interpreting information about the processing of certain therapeutics to inform discussions with a healthcare professional. It does not describe if a person will or will not respond to a particular therapeutic. Our CYP2C19 Pharmacogenetics report provides certain information about variants associated with metabolism of some therapeutics and provides interpretive drug information regarding the potential effect of citalopram and clopidogrel therapy. Our SLCO1B1 Pharmacogenetics report provides certain information about variants associated with the processing of some therapeutics and provides interpretive drug information regarding the potential effect of simvastatin therapy. Our DPYD Pharmacogenetics report does not describe the association between detected variants and any specific therapeutic. Results for DPYD and certain CYP2C19 results should be confirmed by an independent genetic test prescribed by your own healthcare provider before taking any medical action. Warning: Test information should not be used to start, stop, or change any course of treatment and does not test for all possible variants that may affect metabolism or protein function. The PGS test is not a substitute for visits to a healthcare professional. Making changes to your current regimen can lead to harmful side effects or reduced intended benefits of your medication, therefore consult with your healthcare professional before taking any medical action. For important information and limitations regarding Pharmacogenetic reports, visit 23andme.com/test-info/pharmacogenetics/
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