End Show Slide 1 of 39 Copyright Pearson Prentice Hall 12-3 RNA and Protein Synthesis RNA and Protein Synthesis

End Show 12–3 RNA and Protein Synthesis Slide 2 of 39 Copyright Pearson Prentice Hall 12–3 RNA and Protein Synthesis Genes are coded DNA instructions that control the production of proteins. Genetic messages can be decoded by copying part of the nucleotide sequence from DNA into RNA. RNA contains coded information for making proteins.

End Show 12–3 RNA and Protein Synthesis Slide 3 of 39 Copyright Pearson Prentice Hall The Structure of RNA There are four main differences between RNA and DNA: The sugar in RNA is ribose instead of deoxyribose. RNA is single-stranded. DNA is double-stranded. RNA contains uracil in place of thymine. DNA stays in the nucleus, but RNA can leave the nucleus and go into the cytoplasm.

End Show 12–3 RNA and Protein Synthesis Slide 4 of 39 Copyright Pearson Prentice Hall

End Show 12–3 RNA and Protein Synthesis Slide 5 of 39 Copyright Pearson Prentice Hall Types of RNA There are three main types of RNA: Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

End Show 12–3 RNA and Protein Synthesis Slide 6 of 39 Copyright Pearson Prentice Hall Types of RNA Messenger RNA (mRNA) carries copies of instructions for assembling amino acids into proteins.

End Show 12–3 RNA and Protein Synthesis Slide 7 of 39 Copyright Pearson Prentice Hall Types of RNA Ribosomes are made up of proteins and ribosomal RNA (rRNA). Ribosome Ribosomal RNA

End Show 12–3 RNA and Protein Synthesis Slide 8 of 39 Copyright Pearson Prentice Hall Types of RNA During protein construction, transfer RNA (tRNA) transfers each amino acid to the ribosome. Amino acid Transfer RNA

End Show 12–3 RNA and Protein Synthesis Slide 9 of 39 Copyright Pearson Prentice Hall Transcription Protein synthesis begins in the nucleus with a process called transcription. DNA is copied in the form of a single strand of RNA The process begins at a section of DNA called a promoter.

End Show 12–3 RNA and Protein Synthesis Slide 10 of 39 Benefits of Transcription Transcribed copies of the DNA (in the form of RNA) are used instead of the original DNA. In eukaryotes, DNA in the cytoplasm is broken down, but RNA is not. RNA remains intact.

End Show 12–3 RNA and Protein Synthesis Slide 11 of 39 How does Transcription Work? 1.DNA double helix must be separated by breaking the hydrogen bonds between nitrogen bases. 2.Only one DNA strand is “read” by the enzyme RNA polymerase. 3.RNA polymerase constructs an RNA polymer.

End Show 12–3 RNA and Protein Synthesis Slide 12 of 39 An enzyme, RNA Polymerase, acts on the DNA molecule and causes it to unzip. It chemically tells RNA nucleotides to come and base pair with the open DNA molecule according to the base-pairing rules: Adenine-Uracil (A-U) Always Up Guanine-Cytosine (G-C) Going Camping Copyright Pearson Prentice Hall

End Show 12–3 RNA and Protein Synthesis Slide 13 of 39 Copyright Pearson Prentice Hall

End Show 12–3 RNA and Protein Synthesis Slide 14 of 39 Building an RNA Polymer DNA  (codes for) RNA A  U T  A C  G G  C

End Show 12–3 RNA and Protein Synthesis Slide 15 of 39 Copyright Pearson Prentice Hall Transcription RNA RNA polymerase DNA

End Show 12–3 RNA and Protein Synthesis Slide 16 of 39 What happens to RNA once it is created? In prokaryotes, the RNA is immediately translated. In eukaryotes, the RNA is processed. –Introns removed –Exons joined together

End Show 12–3 RNA and Protein Synthesis Slide 17 of 39 Copyright Pearson Prentice Hall RNA Editing Some DNA within a gene is not needed to produce a protein. Remember, DNA stays in the nucleus, but the edited mRNA leaves the nucleus and goes into the cytoplasm to the ribosome

End Show 12–3 RNA and Protein Synthesis Slide 18 of 39 RNA Processing Introns - segments of useless genes. They are removed. Exons – are the expressed genes that remain.

End Show 12–3 RNA and Protein Synthesis Slide 19 of 39 Copyright Pearson Prentice Hall The Genetic Code The genetic code is the “language” of mRNA instructions. The code is written using four “letters” (the bases: A, U, C, and G). Adenine, Uracil, Cytosine, Guanine

End Show 12–3 RNA and Protein Synthesis Slide 20 of 39 Protein SynthesisDNAmolecule DNA strand (template) 3 TRANSCRIPTION Codon mRNA TRANSLATION Protein Amino acid 3 5 5

End Show 12–3 RNA and Protein Synthesis Slide 21 of 39 Copyright Pearson Prentice Hall The Genetic Code A codon consists of three consecutive nucleotides on mRNA that specify a particular amino acid.

End Show 12–3 RNA and Protein Synthesis Slide 22 of 39 Copyright Pearson Prentice Hall The Genetic Code Ribosomes use this decoding system to determine how to build the appropriate protein.