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Mutations A change in the DNA structure There are two categories of mutations Gene Mutation 1. 2. 3. A change in the DNA A change in the sequence of nitrogenous bases Mutagens can cause the change What’s Happened to the DNA? Both had one base substituted for another. How was the DNA changed in these examples? Comparing Gene Mutations Additional Ways DNA Mutated What can a changed protein do to an organism? Changes the reading of the DNA 2. Results in the formations of new mRNA codons leading to a change in the polypeptide structure 3. Types are: insertion or deletion 1. Mutation: Frameshift Identify the category and type of mutation affecting this strand of DNA 1. AUGCCGUACCUUAUGGCUG Mutated Strand reads: 1. AUGCACGUACCU… A 2. AUGC_GUACCUUAUGGCUG 2. AUGCGUACCUUA… Notice that the reading of the DNA will be shifted. Hence, these are frameshift mutations. The mRNA when translated will produce a different amino acid sequence. Human Red Blood Cells Contain the protein, hemoglobin (Hb) 2. O2 binds to Hb = oxygenated blood 3. Red Blood Cells are doughnut shaped cells 1. Sickle Cell Anemia 1. 2. 3. 4. RBC’s are “sickled shape” Hemoglobin protein has been altered -shape has changed Cells stick to each other; Oxygen binding capacity has been altered. Circulatory problems arise Why? Normal Hemoglobin: Valine-Histidine-Leucine-Threonine-Proline-Glutamic Acid-Glutamic Acid Abnormal Hemoglobin: Valine-Histidine-LeucineThreonine-Proline-Valine-Glutamic Acid Sickle Cell Anemia had change in the polypeptide chain: Glutamic acid is changed to Valine Why??????? How can this be?????????????? Normal Hb Sickle Hb DNA: CTT mRNA: GAA Amino Acid: Glutamic acid DNA: CAT mRNA: GUA Amino Acid: Valine …Proline-Glutamic AcidGlutamic Acid… …Proline-Valine-Glutamic Acid… What type of mutation caused the altered hemoglobin? A Point Mutation – base substitution Change Affects Codon This is normal structure Codon Change Affects Protein Structure Chromosomal Mutation Alterations in chromosome number and/or structure Structural Chromosomal Mutations Deletion Duplication Homologous chromosomes Inversion Reciprocal translocation Nonhomologous chromosomes Read 8.22, 8.23, 8.24 Figure 8.23A, B Chromosome Number for a Species Species # of chromosomes Species # of chromosomes Fruit fly 8 Human 46 Rye 14 Ape 48 Guinea Pig 16 Sheep 54 Dove 16 Horse 64 Snail 24 Chicken 78 Earthworm 32 Carp 104 Pig 40 Butterflies ~380 Wheat 42 Fern ~1200 Does the embryo have the correct number of chromosomes? Egg cell Sperm cell zygote Does the zygote have the correct number of chromosomes? Chromosome Number Mutation LE 13-10 Key Maternal set of chromosomes Possibility 2 Possibility 1 Paternal set of chromosomes Two equally probable arrangements of chromosomes at metaphase I Metaphase II Daughter cells Combination 1 Combination 2 Combination 3 Combination 4 Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes Meiosis I Homologous chromosomes separate Haploid cells with replicated chromosomes Meiosis II Sister chromatids separate LE 13-7 Haploid cells with unreplicated chromosomes A karyotype: a photographic inventory of an individual’s chromosomes To study human chromosomes microscopically, researchers stain and display them as a karyotype ◦ A karyotype usually shows 22 pairs of autosomes and one pair of sex chromosomes Additional information 8.19-20 Preparation of a karyotype Blood culture Packed red And white blood cells Hypotonic solution Fixative Stain White Blood cells Centrifuge 3 2 Fluid 1 Centromere Sister chromatids Pair of homologous chromosomes 4 5 Figure 8.19 Let’s look at this Karyotype This karyotype shows three number 21 chromosomes An extra copy of chromosome 21 causes Down syndrome Figure 8.20A, B The chance of having a Down syndrome child goes up with maternal age…why? Figure 8.20C Beginning the Karyotype 1. 2. 3. You will simulate the karyotyping task. You will create a karyotype and determine the gender and developmental status of the baby. You must carefully cut out all chromosomes and correctly match them up by: a. Size of chromosome b. Location of centromere c. Banding pattern on chromosome Karyotype Lab Finished Karyotype Another Karyotype Male or Female?