Cell Differentiation
Cell Specialization & Gene Expression We have 100 trillion cells, but they don’t all look the same (200 types): Neuron Cell Epithelial (Skin) Cells Red Blood Cells Muscle CellSperm Cell
Cell Specialization & Gene Expression All of these cells contain the same exact copy of DNA (except sperm and egg), BUT: Image Source: questgarden.com Same DNA, but only some genes are expressed Definitions **Gene: a portion of DNA that codes for a protein **Gene Expression: the proteins formed by the decoding of specific genes in a cell
Exhibition Step 1 Pick a cell Answer questions on planning sheet Use as introduction to your hero and story
10 Human Mutations
Mutations Mutation: A change in a DNA sequence. May or may not affect gene expression (the protein).
Mutagen: something that causes a mutation
MutationsPointSilentNot SilentFrameshiftInsertionDeletion Mutations & Gene Expression
Image Source: waynesword.palomar.edu Recall: 64 codons, only 20 amino acids.
Mutations Point Mutation: Change in one nucleotide 1. T H E / F A T / C A T / A T E / T H E / R A T T H E / F A T / K A T / A T E / T H E / R A T 2. T H E / F A T / C A T / A T E / T H E / R A T T H E / F A T / B A T / A T E / T H E / R A T “Silent Mutation” Not Silent Message still sounds the same Message sounds different
Mutations & Gene Expression Point Mutations (cont.) Normal: Point (Silent): Point (not silent): DNA Template Strand TACGTGCGAACCTGAATT mRNA Strand AUGCACGCUUGGACUUAA Protein MethionineHistidineAlanineTryptophanThreonineSTOP DNA Template Strand TACGTGCGCACCTGAATT mRNA Strand AUGCACGCGUGGACUUAA Protein MethionineHistidineAlanineTryptophanThreonineSTOP Recall: 64 codons, only 20 amino acids; helps prevent protein changes! DNA Template Strand TACGTGCGAACGTGAATT mRNA Strand AUGCACGCUUGCACUUAA Protein MethionineHistidineAlanineCysteineThreonineSTOP Just one amino acid change can change an entire protein!
Sickle Cell Anemia
Mutations & Gene Expression Frameshift Mutations: insertion or deletion of nucleotide(s) results in the reading of codons to shift. 1. T H E / F A T / C A T / A T E / T H E / R A T T H E / F A E / T C A / T A T / E T H / E R A / T 2. T H E / F A T / C A T / A T E / T H E / R A T T H E / A T C / A T A / T E T / H E R / A T Insertion Letters after insertion are shifted to the right All Nonsense = Message Destroyed Deletion All Nonsense = Message Destroyed Letters after insertion are shifted to the left
Mutations & Gene Expression Frameshift Mutations (cont.) Normal: Frameshift Insertion: Frameshift Deletion: DNA Template Strand TACGTGCGAACCTGAATT mRNA Strand AUGCACGCUUGGACUUAA Protein MethionineHistidineAlanineTryptophanThreonineSTOP DNA Template Strand TACAGTGCGCACCTGAATT mRNA Strand AUGUCACGCGUGGACUUAA Protein MethionineSerineArginineLeucineAspartateLeucine DNA Template Strand TACTGCGAACGTGAATT mRNA Strand AUGACGCUUGCACUUAA Protein MethionineThreonineLeucineGlycineLeucine No Stop Completely Different!
Example Cystic Fibrosis
You try it… Write: THE BOY HAD THE FLU Do two types of frameshift mutations: Insertion of a single base Deletion of a single base In each case, how many amino acids would be affected during translation?
Mutations & Gene Expression Which is more destructive? Point OR Frameshift Changes MANY amino acids MutationsPointSilentNot SilentFrameshiftInsertionDeletion Can be a “silent mutation” or only changes one amino acid
What Causes Mutations? There are two main ways in which DNA can become mutated: Mutagens: agents that cause changes in DNA: Chemical exposure: pH, poisons, toxins, factory waste, pollution Radiation: nuclear fallout, X rays, UV sun exposure video/index.html
Are mutations good or bad? Both…. Mutations can lessen chances of survival A mutation that makes a rabbit white instead of brown may make it easier to catch because it stands out in its environment. Mutations can help chances of survival and increase genetic diversity in a species Over millions of years, mutations have caused different colors in bear fur, and bears have evolved as different species in different environments (polar, forest)
Exhibition Step 2 Pick a mutagen Research how it affects cells, and apply it to your selected cell This is the conflict and introduction of the villain in your story