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5: Flow of Genetic Information

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  • Page ID
    1645
  • As the cell’s so-called blueprint, DNA must be copied to pass on to new cells and its integrity safeguarded. The information in the DNA must also be accessed and transcribed to make the RNA instructions that direct the synthesis of proteins.
    • 5.1: DNA Replication
      The only way to make new cells is by the division of pre-existing cells. This means that all organisms depend on cell division for their continued existence. DNA, as you know, carries the genetic information that each cell needs. Each time a cell divides, all of its DNA must be copied faithfully so that a copy of this information can be passed on to the daughter cell. This process is called DNA replication.
    • 5.2: DNA Repair
      All DNA suffers damage over time, from exposure to ultraviolet and other radiation, as well as from various chemicals in the environment. As you already know, even minor changes in DNA sequence, such as point mutations can sometimes have far-reaching consequences. Likewise, unrepaired damage caused by radiation, environmental chemicals or even normal cellular chemistry can interfere with the accurate transmission of information in DNA.
    • 5.3: Transcription
      You have learned in introductory biology courses that genes, which are instructions for making proteins, are made of DNA. You also know that information in genes is copied into temporary instructions called messenger RNAs that direct the synthesis of specific proteins. This description of flow of information from DNA to RNA to protein, shown on the previous page, is often called the Central Dogma of molecular biology and is a good starting point for an examination of how cells use the info.
    • 5.4: Regulation of Transcription
      The processes described above are required whenever any gene is transcribed. But what determines which genes are transcribed at a given time. What are the molecular switches that turn transcription on or off? The basic mechanism by which transcription is regulated depends on highly specific interactions between transcription regulating proteins and regulatory sequences on DNA. Promoters indicate where transcription begins.
    • 5.5: RNA Processing
      So far, we have looked at the mechanism by which the information in genes (DNA) is transcribed into RNA. The newly made RNA, also known as the primary transcript (the product of transcription is known as a transcript) is further processed before it is functional. Both prokaryotes and eukaryotes process their ribosomal and transfer RNAs.
    • 5.6: Translation
      Translation is the process by which information in mRNAs is used to direct the synthesis of proteins. As you have learned in introductory biology, in eukaryotic cells, this process is carried out in the cytoplasm of the cell, by large RNA-protein machines called ribosomes. Ribosomes contain ribosomal RNAs (rRNAs) and proteins. The proteins and rRNAs are organized into two subunits, a large and a small.

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