Frequently Asked Questions (FAQ)
What is DNA?
Every cell in a person's body contains a chemical called deoxyribonucleic acid (DNA). DNA is like a big instruction book that tells your body how to grow and develop. The shape of DNA is called a "double helix." It looks like a twisted ladder.
The rungs of the ladder are built with the four-letter DNA alphabet, A, C, T, and G. Each letter stands for a nitrogen base component in the DNA chain. The nitrogen bases bond together to make the rungs of the ladder.
Each nitrogen base pairs with only one other nitrogen base. A always bonds with T and C always bonds with G. The sides of the ladder are made of sugar and phosphate components, sometimes called a "backbone". Each DNA subunit, consisting one sugar group (or deoxyribose), one phosphate group and one nitrogen base, is called a nucleotide base.
The DNA inside one cell would stretch about three meters. How does it fit into a cell? The strand of DNA is coiled around special packaging proteins, called histones, that are wound and packed tighter still into a chomosome.
What is a chromosome?
The physical structure of DNA is called a chromosome. Each cell in a human has 46 chromosomes. Everyone inherits half of their chromosomes from their mother and the other half of their chromosomes from their father.
Chromosomes are organized into genes. Each chromosome contains thousands of genes.
What is a gene?
A gene is the heritable unit within a chromosome that is passed along from parent to child. Genes contain pieces of DNA, and most genes contain instructions to make a specific protein.
What is a protein?
Proteins are substances that make our bodies function. A cell can contain thousands of proteins and all of them have a specific role in the cell's function.
Each protein is made of amino acid subunits. There are 20 different amino acids.
The shape of a protein is determined by the different combination of amino acids and how they bond and fold onto each other. It is the unique shape of proteins that is the key to the function within a cell.
How does DNA give the body instructions?
The A, C, T, and G, "alphabet" is put together in different combinations along the stretch of DNA. Before the DNA can give its instructions, it has to be transcribed into messenger RNA (mRNA).
RNA and DNA are very similar molecules. The RNA alphabet also has four letters that represent nucleotide bases. Three bases are the same as the DNA alphabet, A, C, and G, and the fourth base is U.
When the DNA molecule is transcribed into mRNA, the bases pair according to special bonds. The mRNA then travels to an organelle in the cell called a ribosome. The ribosome "reads" the transcribed mRNA sequence.
Each combination of three letters in the mRNA sequence, called a codon, is a code for a specific amino acid. The corresponding amino acid will match to the mRNA sequence. Then the amino acids are linked together to build a protein.
The process of reading and matching amino acids to the mRNA codons and linking amino acids together to produce a protein is called translation.
The resulting protein performs a function in the cell such as sending a chemical message or playing a roll in cell structure.
What is a mutation?
Sometimes, for reasons that are not always known, there are changes in the copy of DNA from parents to children. A change, or mutation, in DNA can be good or beneficial. It can be negative and cause birth defects or other problems. Or it can be neutral and go unnoticed.
What are birth defects?
Birth defects are abnormalities of the structure of a body part and are typically present at birth. They can range from minor to severe or even fatal.
The causes can be primarily environmental or genetic but are usually combination of both.
Approximately 6% of children worldwide are born with a birth defect.