CHAPTER 10 Protein Synthesis

The flow of genetic information in the cell is DNARNAprotein The Central Dogma: Transcription and Translation Bozeman Science https://www.youtube.com/watch?v=yLQe138HY3s The sequence of codons in DNA spells out the primary structure of a polypeptide Polypeptides form proteins that cells and organisms use

Review/Preview-control of Gene expression in Eukaryotes DNA molecule Review/Preview-control of Gene expression in Eukaryotes http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter16/control_of_gene_expression_in_eukaryotes.html Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Amino acid Figure 10.7

Summary of transcription and translation DNA Stage mRNA is transcribed from a DNA template. 1 mRNA RNA polymerase Amino acid TRANSLATION Stage Each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP. 2 Enzyme tRNA Initiator tRNA Anticodon Stage Initiation of polypeptide synthesis 3 Large ribosomal subunit The mRNA, the first tRNA, and the ribosomal subunits come together. Start Codon Small ribosomal subunit mRNA Figure 10.15

Modification of the polypeptide Endoplasmic reticulum Collects proteins made by the ribosomes Packages them into vesicles which move to the Golgi apparatus Golgi apparatus Proteins are altered, packaged into vesicles, and transported to different parts of the cell or exported out of the cell http://vcell.ndsu.edu/animations/proteinmodification/movie-flash.htm

Mutations can change the meaning of genes Mutations are changes in the DNA base sequence These are caused by errors in DNA replication or by mutagens The change of a single DNA nucleotide causes sickle-cell disease

Sickle-cell hemoglobin Normal hemoglobin DNA Mutant hemoglobin DNA mRNA mRNA Normal hemoglobin Sickle-cell hemoglobin Glu Val http://www.cleanvideosearch.com/media/action/yt/watch?videoId=1fN7rOwDyMQ&name=Evolution+of+sickle+cell+malaria&uploadUsername=acorvettes&hitCount=36284 Figure 10.16A

The genetic code is the Rosetta stone of life Virtually all organisms share the same genetic code Figure 10.8A

Types of mutations NORMAL GENE mRNA Protein Met Lys Phe Gly Ala BASE SUBSTITUTION Met Lys Phe Ser Ala BASE DELETION Missing Met Lys Leu Ala His Figure 10.16B

There are 2 general categories of mutations: Base substitution Types of Mutations There are 2 general categories of mutations: Base substitution The replacement of one nucleotide with another Can result in no change in the protein An insignificant change The altered amino acid has no effect on the function of the protein

A change that is crucial to life of the organism Types of Mutations A change that is crucial to life of the organism The altered amino acid has an effect on the function of the protein Base insertions or deletions One or more bases are added or deleted from the DNA Often have disastrous effects The nucleotide sequence following the change alters the genetic message (reading frame)

Mutations are useful because they Provide diversity that allows evolution by natural selection to occur Essential tool for geneticists Create different alleles needed for genetic research