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Mutations From Gene to Protein Honors Biology Ms. Kim.

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1 Mutations From Gene to Protein Honors Biology Ms. Kim

2 Mutations – Are changes in the genetic material (DNA) of a cell 2 TYPES 1. Point mutations can affect protein structure and function – Are changes in just one base pair of a gene

3 POINT MUTATIONS The change of a single nucleotide in the DNA’s template strand – Can lead to the production of – an abnormal protein or… – the same protein

4 Point Mutations Point mutations within a gene are called – Base-pair substitutions Can result in a mutation (change) that is harmful neutral (not harmful or helpful) beneficial

5 Substitutions 2 TYPES – missense (wrong amino acid) ONLY 1 wrong aa is added to polypeptide…all the other aa’s are the same – nonsense (prematurely STOP) The change in DNA leads to an early STOP codon  polypeptide is SHORTEN!!

6 POINT MUTATION ANALOGY… TEMPLATE: THE CAT ATE THE RAT POINT MUTATION: THE CAT ATE THE RAT – THE CAT ATE THE BAT  What kind of point mutation is this? MISSENSE – THE CAT ATE THE XAT  What kind of point mutation is this? NONSENSE

7 What is the “wobble” effect? The last base (nucleotide) in a codon is said to be in the WOBBLE position. – codon mutation may encode the same amino acid Leads to NEUTRAL or SILENT mutations – Not harmful or helpful SILENT MUTATIONS Mutation does not change “end result”…change in DNA still makes the SAME amino acid NO noticeable change occurs a change from AUU to AUC will still encode leucine

8 What is a neutral mutation ? May or may not affect the resulting protein. – For example, if the codon AAA is mutated to AGA, arginine would be used in the resulting protein instead of lysine – These amino acids are chemically similar and may not have a large effect in the protein or its function – IF this change causes the protein to not function (and be LETHAL to the organism) then it is not a neutral mutation but rather a missense mutation

9 2. Frameshift Mutations Insertions and deletions – Are additions or losses of nucleotide pairs in a gene – produce frameshift mutations 2 TYPES – Insertions – Deletions

10 FRAMESHIFT MUTATION ANALOGY… TEMPLATE: THE CAT ATE THE RAT ADDITION of “B” MUTATION: THE CAT ATE THE RAT – THE CAT BAT ETH ERA T  What kind of frameshift mutation is this? INSERTION SUBTRACTION of “A” MUTATION: THE CAT ATE THE RAT – THE CAT TET HER AT  What kind of frameshift mutation is this? DELETION http://highered.mcgraw- hill.com/sites/0072552980/student_view0/chapter9/animatio n_quiz_5.html http://highered.mcgraw- hill.com/sites/0072552980/student_view0/chapter9/animatio n_quiz_5.html

11 Which is more harmful? Typically, frameshift mutations are more harmful BUT some point mutations can be LETHAL – Ex: Tay Sachs and Cystic Fibrosis

12 Other Types of Mutations Inversions – “Flip Flops” Nucleotides trade places on each strand Deletions (2+ nucleotides) – Many nucleotides are deleted at once

13 Causes of Mutations Inherited mutations – From mom and dad Spontaneous mutations – occurs during DNA replication Environmental mutations (Mutagens) – physical or chemical agents that can cause mutations Ex: Sun, viruses, chemicals

14 Belgian Blue Cattle (so beefy….) The Belgian Blue has a natural mutation in myostatin gene, which codes for protein that inhibits muscle development and fat deposition (creates very lean meat).

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16 Piedmontese cattle (still so beefy…)

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