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TRANSLATION and MUTATIONS

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Presentation on theme: "TRANSLATION and MUTATIONS"— Presentation transcript:

1 TRANSLATION and MUTATIONS
12-3, part 2 and 12-4 TRANSLATION and MUTATIONS

2 TRANSLATION translation: the decoding of the mRNA into a polypeptide chain (protein) mRNA is transcribed from DNA in nucleus and moves into cytoplasm mRNA attaches to a ribosome tRNA brings the correct amino acid each tRNA has an anticodon on one end that is complimentary to the codon on mRNA and a corresponding amino acid on the other end

3 TRANSLATION anticodons: three-base sequence on tRNA that is complimentary to an mRNA codon The tRNA molecules are matched to their codons one at a time The first tRNA is UAC, pairing up with AUG on the mRNA. The first codon/anticodon is for the start code and methionine…every protein has methionine as it’s first amino acid

4 mRNA Nucleus Messenger RNA mRNA Lysine Phenylalanine tRNA Transfer RNA
Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome mRNA Start codon

5 TRANSLATION the ribosome joins the first two amino acids and continues to add additional amino acids. the two joined amino acids are transferred to the second amino acid the ribosome moves to the third codon the corresponding tRNA brings in its amino acid

6 TRANSLATION the process continues until the ribosome reaches a stop codon and the polypeptide is released

7 The Polypeptide “Assembly Line” Growing polypeptide chain
The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Translation direction Ribosome

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9 12-4 Mutations

10 Gene Mutations mutations: changes in the DNA sequence that affect genetic information point mutations: mutations that affect one nucleotide base substitution: a substitution of one nucleotide for another may or may not cause a change in the amino acid sequence of the affected protein

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12 Gene Mutations frameshift mutations: mutations caused by the addition or deletion of a nucleotide Can either ADD a base, or DELETE a base.

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14 Chromosomal Mutations
involves changes in the number or structure of chromosomes changes in gene locations or the number of copies of genes

15 Deletion Duplication Inversion Translocation


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