Genes And Alleles

Define Gene

An heritable factor that controls a specific characteristic, consiting of a length of DNA occupying a position on a chromosone known as a locus.

An allele is any one of a number of alternative forms of the same gene occupying a given locus (position) on a chromosome. An example is the gene for blossom color in many species of flower - a single gene controls the color of the petals, but there may be several different versions of the gene. One version might result in red petals, while another might result in white petals.

Many organisms are diploid - that is, they have two sets of homologous chromosomes in their somatic cells, and thus contain two copies of each gene. An organism in which both copies of the gene are identical - that is, have the same allele - is said to be homozygous for that gene. An organism which has two different alleles of the gene is said to be heterozygous. Often one allele is "dominant" and the other is "recessive" - the "dominant" allele will determine what trait is expressed. For example, in the case of blossom color, if the "red" allele is dominant to the "white" allele, in a heterozygous flower (with one red and one white allele), the petals will be red.

Genes are instruction manuals for a bodies. They are the directions for the building up all the proteins which make are bodys function.Genes are made of dna. One starnd if our dna contains may genes. All of these genes are needed to give instructions for how to make and operate all parts of our bodies.If a gene is normal it will work fine, however if the instrucyion in that gene is changed, or "mutated" changes in the gene could result in a mutation. Genes contain instructions for building proteins which are invloved in al sorts of things eg hemoglobin protein, the enzymes which produce the pigment in your eyes and Keratin, responsible for growing hair and nails are also produced by genes.

Instructions in the form of DNA molecules reside inside the nucleus of a cell and tell it which role it plays within the body. Dna stands for DeoxyriboNucleic Acid. Dna comes in the form of a twisted shape scientists call a dounle helix. The ladder rungs are built with the four letter DNA alphabet: A C T and G. These alphabet piecesjoin together according to special rules: A always pairs with T and c always pairs with G.

G=Guanine

A= Adenine

T=Thymine

C= Cytosine

These letters join up to make genes. Genes tell the cell to make other molecules called proteins. Proteins enable a cell to perform special functions, such as working with other groups of cells to make hearing possible.

Each cell in our body contains a lot of DNA , if you pulled the DNA from a single human cell it would measure 3 metres long!This DNA is therefore packaged into chromosomes.Each human has 46 chromosomes.All DNA is organized into 2 sets of 23 chromosomes.Not all living things have the same amount of chromosomes.

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