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1. What is the Human Genome?

 

The Genome is the collection of all the genes contained in an organism. It is a chemical code, similar to a computer code that instructs a computer how to operate, and this code is found in each of the 100 trillion cells in your body. The human genome controls the manufacturing and building for the entire human body. All this information is contained in a cell at the very beginning of life, as soon as a sperm fertilizes an egg. This "one-cell zygote" divides and duplicates the entire genome into the two cells it produces. Those two cells divide and double and so on. This process continues and DNA remarkably controls the differentiation of cells into each of the 210 different varieties of tissues in the human body, from your teeth to your toenails and your corneas to your cardiac system. The entire genome is contained in every cell of an adult human’s body, but through a poorly understood control mechanism, the DNA only "expresses" part of the code in each cell, depending on the cell’s function.¹

 

 

How Does It Work?

 

Image Source: U.S. Department of Energy Human Genome Program

1. Chromosomes: All the DNA in a single cell is on 46 chromosomes - 23 from the father and 23 from the mother (half from each). One of the chromosomes given from each parent is an "X" or "Y" chromosome. Women can only give "X" but men can give "X" or "Y". If he gives an "X" chromosome, the child is a girl. If he passes down a "Y" chromosome, the child is a boy.

 

2. DNA: The chromosomes are made of DeoxyriboNucleic Acid (DNA). The DNA on all the chromosomes is about 2 meters, or 6 feet long and measures 50 trillionth of an inch wide. If you put all the DNA in your body end to end it would wrap around the globe a total of 4,734,848 times.

 

3. Nucleotides: DNA is a twisted ladder-like molecule. The side of the ladder is made of sugars and phosphates. The rungs of the ladder are made of four nitrogen compounds: adenine (A), thymine (T), cytosine (C), and guanine (G)]. One rung of the ladder with its side rails equals a nucleotide. Cytosine always pairs with guanine and thymine always pairs with adenine. This gives four possible letter codes (CG, GC, TA or AT), which are called base pairs.

 

4. Proteins: The sequence of this "digital" code controls the production of amino acids which make up proteins, the basic building blocks for all the structure and function in the human body.

 

Image Source:  U.S. Department of Energy Human Genome Program

• There are only twenty amino acids.

• Three base pairs in the gene code for one amino acid.

• The proteins made are determined by the DNA in each cell.

 

Proteins make up your muscle, lungs, hormones, digestive enzymes and much more of what makes your body work. There are approximately 30-40,000 different proteins in the human body.

 

Image Source:  U.S. Department of Energy Human Genome Program

 

 

5. Genes

• An average of 3,000 base pairs make a gene.

   

• There are about 30 - 40,000 genes in the 46 chromosomes.

   

• Genes only make up 5 percent of chromosomes.

   

• The other 95 percent of DNA is part of the regulatory mechanism and/or has unknown functions.

 

All people are born with missing or damaged genes. That means you have 50-60 abnormal genes. Most people have no visible effects but some abnormal genes cause an increased risk of cancer, diabetes or other diseases. Some defects are passed down from parents; that is why some diseases run in families. For example, there is a gene that markedly increases the risk for colon cancer at a young age. Cystic Fibrosis (a defect of three base pairs that causes thick secretions resulting in recurrent pneumonia and early death) has a familial component. Other defects happen through mutations. When the cell divides to reproduce itself, it must replicate its DNA. The twisted ladders split forming two strands and an identical copy of the other side of the "ladder" is made. If a mistake is made, it can be passed on to subsequent cells. Some cancers and other genetic defects are caused in this manner. Other damage is due to radiation or other environmental injury to DNA.

 

 

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