The Genetic Basics: What Are Genes and What Do They Do? – A …

Chromosomes contain the recipe for making a living thing. They are found in almost every cells nucleus and are made from strands of DNA (deoxyribonucleic acid). Segments of DNA called "genes" are the ingredients. Each gene adds a specific protein to the recipe. Proteins build, regulate and maintain your body. For instance, they build bones, enable muscles to move, control digestion, and keep your heart beating.

Two of these 46 chromosomes determine the sex of a person. A girl inherits two X-chromosomes, one from her mother and one from her father. A boy inherits one X-chromosome from his mother and a small Y-chromosome from his father.

A gene can exist in many different forms, calledalleles. For example, lets say that there is one gene which determines the color of your hair. That one gene may have many forms, or alleles: black hair, brown hair, auburn hair, red hair, blond hair, etc. You inherit one allele for each gene from your mother and one from your father.

Each of the two alleles you inherit for a gene each may be strong ("dominant") or weak ("recessive"). When an allele is dominant, it means that the physical characteristic ("trait") it codes for usually is expressed, or shown, in the living organism. You need only one dominant allele to express a dominant trait. You need two recessivealleles to show a recessive form of a trait. See the heredity diagram for tongue rolling to see how dominant and recessive alleles work.

Tongue Rolling Heredity Diagram

There are several ways the genetic code can be altered. Sometimes genes are deleted or in the wrong place on a chromosome, or pieces of genes are swapped between chromosomes. As a result, the gene may not work or may turn on in the wrong part of the body.

"Point mutations" alter the genetic code by changing the letters in the codons -- the three-symbol genetic words that specify which protein to make. This can change the protein.

Original message: SAM AND TOM ATE THE HAM

Kind of point mutation

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The Genetic Basics: What Are Genes and What Do They Do? - A ...