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chapter 12 D NA and RNA Genes and Proteins

chapter 12 D NA and RNA Genes and Proteins. Honors Biology. Genes and Proteins. Genes contain instructions for assembling proteins Proteins are enzymes that catalyze and regulate chemical reactions Genes code for enzymes that control pigment (skin or petal color)

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chapter 12 D NA and RNA Genes and Proteins

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  1. chapter 12DNA and RNA Genes and Proteins Honors Biology

  2. Genes and Proteins • Genes contain instructions for assembling proteins • Proteins are enzymes that catalyze and regulate chemical reactions • Genes code for enzymes that control pigment (skin or petal color) • Proteins regulate the rate & pattern of growth throughout an organism, controlling size and shape (design of an organism)

  3. Mutations • Mistakes in copying DNA are often made (incorrect base or deleting or inserting bases) • Mutation – changes in genetic material • Gene mutation – changes in single genes • Chromosomal mutation – changes in whole chromosome

  4. Gene Mutations • Mutations in genes in 1 or a few nucleotides • 2 types of gene mutations • Point Mutations – occur at single point in DNA • Substitutions – 1 base changed to another • Frameshift Mutations –shifts every codon that follows. A shift in reading the entire genetic message • Insertions or deletions of bases • Changes all subsequent amino acids and may change protein

  5. Video 7

  6. Video 7

  7. Point vsFrameshift Mutations insertion deletion substitution Deletion Insertion Substitution

  8. Chromosomal Mutations • Chromosomal Mutations – Changes in number or structure of chromosomes • Down syndrome

  9. Significance of Mutations • Most mutations are neutral, meaning they have little or no effect on the genes or the protein they code for • Mutations are the source of genetic variability in species (various environments) • May be harmful or beneficial • Genetic disorders • Cancer • Adaptations

  10. Gene Regulation • Not all genes are expressed simultaneously, some remain “silent” by being turned on or off • All cells contain the same copy of DNA, however they do not all express the same proteins • Hemoglobin in red blood cells • Keratin in skin cells • Known as cell specialization - only a tiny fraction of available genes are expressed in appropriate cells

  11. Gene Regulation • Every cell develops from same fertilized egg cell • During cell specialization, cells undergo differentiation and become specialized in structure and function • Series of genes called Hox Genes control differentiation of cells and tissues in the embryo. Known as the “master control genes” • Mutation of Hox Gene can completely change organs that develop in specific part of body • In fruit flies, replacement of antennae on head with legs

  12. Gene Regulation Fruit fly head showing the effects of the Antennapedia gene. This fly has legs where its antennae should be. Normal fruit fly head.

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