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DNA Structure & Function

DNA is the commonly used acronym for deoxyribonucleic acid. DNA contains the genetic information of an organism, according to Minnesota State University. All organisms contain DNA which allows the synthesis of essential proteins and enzymes. Additionally, DNA can reproduce itself in a process called replication. Approximately 5 feet of DNA is compressed and coiled in the nucleus of each cell.

  1. DNA Structure

    • DNA is made of repeating units which are referred to as nucleotides, according to Cleveland Hickman Ph.D., Larry Roberts Sc.D. and Allan Larson Ph.D. in their book "Integrated Principles of Zoology." A nucleotide is composed of a phosphate group, a nitrogenous base and deoxyribose, a sugar. DNA is shaped like a twisted ladder and this structure is called a double helix. The phosphate group in DNA is bound with deoxyribose and forms the upright parts of the ladder structure, called the backbones. The nitrogenous bases form the rungs between the backbones.

    DNA Backbones

    • The nitrogenous bases bind the backbones together. But the two backbones are antiparallel, meaning the information on each backbone reads in the opposite direction. The beginning of one backbone is connected through nitrogenous bases to the end of the other backbone.

    Nitrogenous Bases

    • Thymine, adenine, guanine and cytosine are the four nitrogenous bases found in DNA. Their order and placement are what give DNA its twisted shape. Thymine can only attach to adenine and cytosine only attaches to guanine. For example, on one side of a DNA strand, a section of the backbone may contain an adenine base. The other backbone that connects to that section must have a thymine base to attach to the adenine base. These specific pairings continue along the length of the DNA strand. This makes the two backbones complimentary.

    DNA Function

    • DNA directs the synthesis of proteins and enzymes necessary for the life of the organism. The process of this synthesis requires several steps of relaying information from the DNA to other molecules. These steps are called transcription and translation.

    Transcription

    • DNA holds the information that is necessary to create proteins. But it does not directly act in protein synthesis. An intermediary is used to take information from DNA to make protein. The intermediary is a molecule called messenger RNA (mRNA). Transcription is the transfer of information from one of the DNA backbones to mRNA. Translation follows the transcription step.

    Translation

    • During translation, the mRNA attaches to ribosomes which are cell structures located just outside the nucleus. Ribosomes help create proteins. The mRNA uses the information from the DNA to control which amino acids are used to produce specific proteins. The process of translation is so efficient that 500 amino acids can be gathered and used to create a protein within 30 seconds.

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