Protein Synthesis

1. Protein Synthesis Chapter 12

2. Nucleotides • Nucleotide consists of: • 5-carbon sugar – deoxyribose • Phosphate group • One of 4 nitrogen bases • Adenine • Thymine • Guanine • Cytosine

3. Nitrogen Bases • Base pair rule • Adenine always pairs with thymine • A:T • Guanine always pairs with cytosine • G:C • Adenine and guanine are purines • Thymine and cytosine are pyrimidines • Bases are held together by hydrogen bonds (weak)

4. Genetic Code • A gene is a segment of DNA (on a chromosome) that codes for a protein. • Genes determine all traits for all organisms • Genetic code is common for all living things • The sequence of bases determines this code

5. Central Dogma • DNA located in nucleus but proteins are made in ribosomes • How do we get DNA out of nucleus to ribosomes? • Genetic information flows from DNA – RNA – proteins which are expressed as traits • Central Dogma (DNA/gene – RNA – Protein) • DNA contains all information needed for protein synthesis • Info contained in nucleotide sequence

6. Protein Synthesis • Importance • Organisms make the necessary proteins using protein synthesis • Location of proteins • Cell membranes • Cytoplasm • Organelles • Make up enzymes • Each cell must have right kind of proteins to keep the organism alive

7. Protein Synthesis • Definition • Process by which an organism's genotype (genetic make up) is translated into its phenotype (trait) by making the proteins the organism needs • The sequence of DNA bases determines the composition of the protein • Change in nucleotide = different trait

8. RNA • Ribonucleic acid (RNA) • DNA works with RNA to produce proteins

9. DNA vs RNA

10. DNA vs RNA

12. RNA • There are 3 types of RNA • Messenger RNA (mRNA) • Function: relays DNA/genetic sequence information to ribosome to make protein • Transfer RNA (tRNA) • Function: carries the correct amino acid to ribosome to make the protein • Ribosomal RNA (rRNA) • Found in ribosome

13. RNA and Transcription • 1st stage of protein synthesis • Genetic info. from DNA is copied into mRNA • Location: Nucleus • Occurs inside nucleus • Portion (gene or section that codes for protein) of DNA uncoils at hydrogen bonds • RNA polymerase binds to DNA at promoters and separates 2 strands exposing base pairs • Promoters signal RNA where to begin transcription (intiations) • RNA polymerase matches RNA bases with one strand of DNA and links together RNA nucleotides (A:U not A:T) until promoters signal stop (termination)

14. RNA and Transcription • In eukaryotes, an mRNA strand must be edited removing sections that do not code for proteins known asintrons(interrupt) and keeping exons (expressed) or the sections that code for proteins • Now mRNA is ready to leave the nucleus and move to the ribosomes in the cytoplasm of the cell • Transcription occurs continuously along the DNA strand

15. http://www.hhmi.org/biointeractive/media/DNAi_transcription_vo1-lg.movhttp://www.hhmi.org/biointeractive/media/DNAi_transcription_vo1-lg.mov http://www.hhmi.org/biointeractive/media/DNAi_mrna_splicing-lg.mov

16. Practice DNA: TAC TTT AAC GGC GAG AAC ATG mRNA:

17. RNA and Translation • 2nd stage of protein synthesis • Process where “language” of nucleic acids is changed into language of proteins • 20 amino acids • Genetic info. carried by mRNA is translated to form proteins (amino acid chains) • Location: ribosomes (in cytoplasm)

18. Steps of Translation • In the cytoplasm, mRNA attaches to a ribosome and is ready to synthesize a protein (read 5’ – 3’) • A tRNA molecule transfers an amino acid to the ribosome • The tRNA anticodon meets the mRNA codon. Each new amino acid links (peptide bond) with the previous amino acid forming an amino acid chain known as a polypeptide chain • The lengthening of the amino acid chain is called elongation

19. Translation http://www.hhmi.org/biointeractive/media/DNAi_translation_vo1-lg.mov

20. Translation • UCGCACGGU • The sequence would be read three bases at a time as • UCG-CAC-GGU • The codons represent the different amino acids • Serine-Histidine-Glycine

21. Translation • To correctly sequence the amino acids, codons and anticodons are used • A codon = a 3 base section of mRNA that codes for a specific amino acid • Ex. GCU = alanine • An anticodon = a 3 base section of tRNA that brings in the amino acid needed to match with a codon • Anticodons and codons link together inside the ribosome to form an amino acid chain • Once tRNA has dropped off its amino acids the peptide bond is broken and tRNA is released to return to the cytoplasm to pick up another amino acid

22. Practice DNA: TAC TTT AAC GGC GAG AAC ATG mRNA: Protein: http://www.hhmi.org/biointeractive/media/DNAi_triplet_code-lg.mov

23. Amino Acids • Since there are only 4 nucleotides but there are 20 amino acids, there are not enough different nuclotides for each one to code for a different AA • Many codons represent same amino acid • Practice reading chart…

24. How do proteins leave cell • Once protein is complete, where does it go? (how does it leave the cell?)

25. Practice • tRNA anticodon is: UCA • mRNA codon is: _________ • DNA strand is: ___________ • Amino acid is: ___________ (see page 303)

26. http://www.hhmi.org/biointeractive/media/DNAi_damage_mutation-lg.movhttp://www.hhmi.org/biointeractive/media/DNAi_damage_mutation-lg.mov Mutations • Random change in the sequence of nucleotides in DNA • Chromosomal mutation – changes in structures of chromosome • Deletion – when piece of chromosome breaks and piece is lost. • Most deletions are lethal • Duplication – part of chromosome breaks off and is incorporated into its homologous chromosome. • Result is too few or too many genes

27. Mutations • Chromosomal mutations (continued) • Translocation – chromosome breaks off and attaches to different, non-homologous chromosome • Result is too many or too few in a chromosome • Inversion – part of the chromosome breaks, turns around and attaches in the reverse order

28. Gene Mutations • Errors occur within indiv. genes in chromosome • Frameshift mutation – deletions or additions of nucleotides that disrupts codons - alters order of base • The earlier in the sequence it occurs, the more serious the effect THE CAT ATE THE FAT RAT THE ATA TET HER ATA RA_ THE CAT ATE THE FAT RAT THH ECA TAT ETH EFA TRA T

29. http://www.hhmi.org/biointeractive/media/DNAi_sicklecell-lg.movhttp://www.hhmi.org/biointeractive/media/DNAi_sicklecell-lg.mov Sickle Cell Anemia • Point mutations – change that occurs in only one nucleotide (usually substitution) - prod. no change in proteins - prod. normal or defective protein - code for stopping THE CAT ATE THE FAT RAT THE BAT ATE THE FAT RAT • Ex. Sickle cell anemia is a substitution mutation • Be sure you know information about this disorder

30. Review of Processes Review of all processes http://www.learnerstv.com/animation/animation.php?ani=326&cat=biology Review of protein synthesis http://www.learnerstv.com/animation/animation.php?ani=181&cat=Biology Interactive Review http://learn.genetics.utah.edu/content/begin/dna/transcribe/

31. Genetic Engineering • DNA fingerprinting • Uses restriction enzymes to cut DNA. If a sample matches a suspect using gel electrophoresis they can be tied to a scene. • Cell Transformation • Can join human DNA to bacterial DNA to make various hormones in high abundance • What other type of genetic modifications do you know?