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Changes to the Genetic Code

Changes to the Genetic Code. pp. 224-226 and 231. Alterations to the Code. A change in one or many genetic traits Can be either 1) chromosomal or 2) a gene mutation Can happen in gametes or body cells If the change occurs in the gametes the trait can be inherited by the offspring

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Changes to the Genetic Code

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  1. Changes to the Genetic Code pp. 224-226 and 231

  2. Alterations to the Code • A change in one or many genetic traits • Can be either 1) chromosomal or 2) a gene mutation • Can happen in gametes or body cells • If the change occurs in the gametes the trait can be inherited by the offspring • Can be lethal (deadly) even before birth • Typically, changes in the body cells could result in cancer

  3. Chromosomal Alterations • More than 1 trait can be affected since whole segments of DNA can be altered

  4. Deletion • loss of a piece of chromosome

  5. Inversion • Chromosome breaks off and reattaches in reverse EX. Hemophilia

  6. Translocation • Piece breaks off and attaches to another

  7. Gene Mutations • A change in the genetic code of one gene • Typically only one trait is affected

  8. Types of Mutations • Silent: a normal protein is still made • Missense: faulty protein produced • Nonsense: an incomplete protein is made due to an early stop

  9. Causes of the Mutations • Results from a substitution, addition, or removal of a nucleotide • Also called a point mutation

  10. Frame shift mutation • Due to the removal or addition of a nucleotide • Causes shift in entire reading frame and results in an entirely different protein (missense) or no protein due to an early stop (nonsense)

  11. Substitution • Makes a new codon that could result in the same amino acid (silent mutation) • A new codon can also result in an early stop (nonsense) • The structure of the protein can be altered if a different amino acid is made (missense) EX. Sickle cell anemia

  12. What is Sickle Cell Anemia? • A blood disorder with abnormal hemoglobin

  13. What is Hemoglobin? • Hemoglobin is a protein found in red blood cells • Hemoglobin is made up of 4 polypeptide subunits • Hemoglobin carries oxygen which is needed in body tissues

  14. What happens when the HBB gene is mutated? Individuals with sickle cell anemia are homozygous for the “sickle” allele of hemoglobin β (i.e., HSHS) Individuals with one working allele and one “sickle” allele (i.e., HAHS) are heterozygous carriers and have limited symptoms

  15. The problem is that the hemoglobin tetramers made with HbS beta-globin are “sticky” and clump to form long fibers. These long fibers cause the red blood cell to have a sickle shape.

  16. Genotype Phenotype Hemoglobin protein Red blood cell Person

  17. Genotype (HbA/HbA) Phenotype Hemoglobin protein Red blood cell Person Normal tetramers Normal in shape (donut) and number Normal

  18. Genotype (HbS/HbS) Phenotype Hemoglobin protein Red blood cell(RBC) Person Tetramers stick together and form long fibers Abnormal shape (sickle), fewer RBCs Sickle cell anemia

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