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Our bodies are made up of billions of cells, and each cell carries a full set of instructions called a Genome. The gemone intructs every cell how to develop and grow, defining if it is a skin cell, a bone cell or one of the other hundreds of unique body cell types we need to make us work! The genome is made up of DNA (the building blocks or base pairs) which holds the code ( instruction manual). Segments of DNA that code for a specific pupose are called genes.
We have many thousands of genes that provide information for our body to grow, develop and stay healthy, but they only make up aprroximately 5% of the gemone, we do not understand all the functions of the rest of DNA (non-coding regions), but we know they can be important for controlling how our genes work. DNA is about 3 billion base-pairs and is a long double helix chain (think a spiralling ladder).
We each typically have 23 pairs of chromosomes, 46 in total.
Every one of us carries two copies of most genes. One copy was inherited from your mother, the other, from your father. These different versions of the same gene are called alleles. The DNA between each of us is 99% identical, the remainin 1% is different, and this is what makes you unique. Families tend to be more similar in their genes than unrelated individuals.
Generally, DNA variations that have no impact on our health are called benign variants or polymorphisms. Less commonly, variations can change the gene so that it sends a different message. These changes may mean that the gene does not work properly or works in a different way that is harmful. A variation in a gene that causes a health or developmental condition is called a pathogenic variant or mutation.
.jpg "Gene to DNA and Chromosome in cell structure")
The DNA is tightly coiled into chromosomes and is located within the cell nucleus
This thread is tightly wrapped around histones, into what we call chromosomes. This is important as it makes them small enough to fit into the nucleus (center) of our cells. We each typically have 23 pairs of chromosomes (46 in total) you recieve one chromosome from each parent to make a pair. Numbers 1-22 of these chromosome pairs are the same (autosomes). The 23rd pair is made up of the sex chromosomes called X and Y. Usually males have a XY chromosome pair and females have XX.
You recieve one chromosome from each parent to make a pair.