MUTATIONS Transcription DNA m RNA Amino acid RNA

MUTATIONS

Transcription DNA m. RNA Amino acid RNA polymerase 1 m. RNA is transcribed from a DNA template. Translation 2 Each amino acid attaches to its proper t. RNA with the help of a specific enzyme and ATP. Enzyme ATP t. RNA Anticodon Large ribosomal subunit Initiator t. RNA 3 Initiation of polypeptide synthesis The m. RNA, the first t. RNA, and the ribosomal sub-units come together. Start Codon m. RNA Small ribosomal subunit

Mutations can change the meaning of genes § A mutation is a change in the nucleotide sequence of DNA § Mutations can be – Spontaneous: errors in DNA replication or recombination (chromosomes) – Induced by mutagens – High-energy radiation – Chemicals Copyright © 2009 Pearson Education, Inc.

POINT MUTATION Replacement of one nucleotide with another – ONLY MATTERS IF: – CHANGES Amino acid CHANGES function of the protein Normal hemoglobin DNA Mutant hemoglobin DNA m. RNA Normal hemoglobin Sickle-cell hemoglobin Glu Val Copyright © 2009 Pearson Education, Inc.

DELETION – A BASE IS LOST INSERTION – AN EXTRA BASE IS INSERTED RESULT: FRAME-SHIFT (HOW YOU READ); DOWNSTREAM - AMINO ACID CHANGES - WRONG PROTEIN - NO PROTEIN

INSERTION The big red pig ate the red rag. The big res dpi gat eth ere dra g. DELETION The big red pig ate the red rag. The big rep iga tet her edr ag.

SUBSTITUTION – A SINGLE BASE CHANGES RESULT: - MISSENSE MUTATION- WRONG AMINO ACID - WRONG PROTEIN - SILENT MUTATION- SAME AMINO ACID - CORRECT PROTEIN - NONSENSE MUTATION- EARLY STOP CODON - SHORTENED/WRONG PROTEIN

MISSENSE The big red pig ate the red rag. The big res pig ate the red rag. NONSENSE The big red pig ate the red rag. The big re.

Normal gene m. RNA Protein Met Lys Phe Gly Ala Lys Phe Ser Ala Base substitution Met Base deletion Met Missing Lys Leu Ala His