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DNA |
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This is the hereditary material of man and all other life forms. It exists in all the cells of the
body and encodes all human properties. Most of the DNA is concentrated in
the cell nucleus and organized in bodies known as chromosomes. Each
chromosome contains long sequences of DNA divided into thousands of genes.
Each gene is composed of many bases, represented by letters (10,000 on
average), and all the genes are responsible for forming proteins or enzymes
(proteins participating in living processes) that are important for the
body's functioning. A change in the sequence of the bases in a gene may
cause a defect in the formation of a protein or enzyme, and this defect is
expressed as a genetic disease. The changes that result in disease are
called mutations. Every gene has a different function, so mutations in
different genes will cause different diseases.
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Genes |
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Genes encode all the hereditary traits and diseases.
They are composed of long, complex sequences of bases,
which together with sugars and phosphate groups make chemicals
known as nucleic acids, and together they constitute the genetic code. Each
group of 3 bases is called a triplet, and each triplet encodes a single
amino acid. A sequence of amino acids constitutes the final protein. Thus it
can be seen that proteins are the products of genes.
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How many genes are there? |
| The human genome is estimated to contain about 60,000
different genes, each of which is responsible for a different trait/disease.
Each person has 2 copies of each gene - one maternal and one paternal - giving a
total of 2 x 60,000 genes.
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Mutations |
| These are changes in the sequence of the bases that make up the structure of
the gene. These changes include substitutions, insertions, deletions, and
incorrect sequences, and they may cause genetic syndromes if they occur in
certain specific genes.
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DNA Structure
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