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Heredity and DNA Science Study Guide (page 2)

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Updated on Sep 22, 2011

Molecular Basis of Heredity

Like the rest of the body, heredity is dependent on the functioning of biological molecules. The molecule at the basis of heredity is the long, chain polymer we call deoxyribonucleic acid or, more familiarly, DNA. A gene consists of DNA molecules, which are known as polymers. A polymer is a very large molecule made up of many similarly repeating units (called nucleotides in DNA). The shape of the DNA molecule is a double spiral or helix, sort of like a winding staircase with a handrail on each side.

In what is known as the Central Dogma of biology, DNA contains hereditary information, which is transferred (or transcribed) into another molecule called ribonucleic acid (RNA), which is then transformed (or translated) into proteins. It is these protein molecules that are responsible for the expression of inherited traits.

Four special molecules called nucleotides are contained within the structure of the larger DNA molecule. These nucleotides are known as adenine, cytosine, guanine, and thymine. They are commonly abbreviated by their first letters to A, C, G, and T. The arrangement of these nucleotides forms a code that can contain hereditary information. Special enzymes in the cell nucleus read this code and transcribe it into an RNA molecule, specifically known as messenger RNA, because it takes the coded message from the nucleus into the cell's cytoplasm. It is here that the small organelles called ribosomes translate the coded messenger RNA into protein molecules. These protein molecules are either destined to become structural components (such as in the muscles) or enzymes where they will regulate metabolic reactions. These proteins give us our inherited traits.

Human beings have been manipulating this process for thousands of years. We perform this process when we breed crop animals or plants. In the past, we were clever but not very sophisticated because we had to find the best animal or plant and breed it until we achieved the desired crop. The corn we eat today is very different than the plant called maize from which it was bred. The more sophisticated and technically challenging manipulation of an organism's DNA that we perform today is called genetic engineering and is part of the biotechnology industry.

In Short

Organisms exhibit characteristics that define them, such as an elephant having a trunk, an oak tree having green leaves, and humans having large brains. All these characteristics were inherited from parent organisms that looked and acted similarly. These heritable characteristics are transmitted on structures we call genes and chromosomes. Biologists refer to the genetic makeup of an organism as its genotype. However, the collection of physical characteristics that result from the action of genes is called an organism's phenotype. The molecule at the basis of heredity is the long, chain polymer we call deoxyribonucleic acid or DNA. A gene consists of molecules of DNA. In what is known as the Central Dogma of biology, DNA contains hereditary information, which is transferred (or transcribed) into another molecule called ribonucleic acid (RNA), which is then transformed (or translated) into proteins. These protein molecules are responsible for the expression of inherited traits.

Practice problems of this concept can be found at: Heredity and DNA Science Practice Questions

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