RNA & Protein Synthesis

1. RNA & Protein Synthesis

2. RNA and Protein Synthesis • Genes are coded DNA instructions that control the production of proteins within the cell • DNA codes for PROTEINS • Must copy part of the nucleotide sequence from DNA into RNA (ribonucleic acid) which then helps make proteins • Proteins are made in ribosomes – need RNA to go to ribosomes as the DNA cannot leave the nucleus

3. Structure of RNA • Long chain of nucleotides • A 5-carbon sugar (ribose) • A phosphate group • And nitrogenous bases • Differences between RNA and DNA: • Ribose (RNA) vs. deoxyribose (DNA) • RNA is single-stranded, DNA is double-stranded • RNA has Uracil (U) in place of Thymine (T) • In RNA, A bonds with U, and C bonds with G • RNA is a disposable copy of DNA – it is a working copy of a single gene

4. RNA Base-Pairing Rule A = U G = C

5. Types of RNA • Protein synthesis – assembly of amino acids into proteins controlled by RNA • Three types of RNA • Messenger RNA (mRNA) – carry copies of instructions for making amino acids • Ribosomal RNA (rRNA) – proteins assembled on ribosomes • Transfer RNA (tRNA) – transfers each amino acid to ribosome mRNA tRNA

6. Messenger RNA Ribosomal RNA Transfer RNA Bringamino acids toribosome Combine with proteins tRNA mRNA Carry instructions rRNA DNA Ribosome Ribosomes Types of RNA RNA can be also called which functions to also called which functions to also called from to to make up

7. Transcription: DNA RNA • Occurs in NUCLEUS • mRNA produced by copying part of the nucleotide sequence of DNA into a complementary sequence in mRNA = transcription • During transcription, RNA polymerase (similar to DNA polymerase) binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template from which nucleotides are assembled into a strand of mRNA • RNA polymerase binds to specific regions of DNA in order to start making mRNA

8. Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA

9. Transcription

10. The Genetic Code & Intro to Translation • Translation is taking mRNA and making proteins • Proteins code for traits! • Proteins are made by joining amino acids into long chains called polypeptides • There are 20 different amino acids – the order of amino acids determine what proteins will be made • “Language” of mRNA instructions is the genetic code – codes for proteins • RNA contains four bases A, U, C, and G – where A and U can bond together and C and G can bond together

11. The Genetic Code (continued) • Genetic code is read THREE letters at a time, so that each “word” of coded message is 3 bases long. Each 3 letter “word” in mRNA is called a codon which identifies a single amino acid used in a protein Example: mRNA sequence – UCGCACGGU Read 3 bases at a time – UCG – CAC – GGU Codons represent different amino acids UCG – CAC – GGU Serine – Histadine – Glycine What is the DNA sequence that coded for this mRNA sequence? AGCGTGCCA

12. The Genetic Code mRNA Sequence: UCG CAC GGU

13. The Genetic Code (continued) • Some amino acids can be specified by more than one codon (because there are only 20 amino acids, and 64 possible codons, some codons will overlap) • 3 “stop” codons – signal the end of a protein • Codon AUG specifies methionine – a “start” codon for the beginning of the protein • A chart is used to decode the codons into their respective amino acids

14. mRNA Sequence: UCG CAC GGU