1 / 33

During translation, new tRNAs carrying amino acids enter of the ribosome.

During translation, new tRNAs carrying amino acids enter of the ribosome. The A site The P site The E site The X site. Which of the following is NOT true about translation?. Peptide bonds form between the amino acids held by the tRNAs in the P and A positions

elaine-lowery
Download Presentation

During translation, new tRNAs carrying amino acids enter of the ribosome.

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. During translation, new tRNAs carrying amino acids enter of the ribosome. • The A site • The P site • The E site • The X site

  2. Which of the following is NOT true about translation? • Peptide bonds form between the amino acids held by the tRNAs in the P and A positions • tRNAs leave the ribosome from the E position • tRNAs carrying their amino acids enter the ribosome initially at the P site • Amino acids are initially bound to tRNAs at their carboxyl ends

  3. Cycle repeats… tRNA in E site exits, and cycle repeats (new tRNA binds to A site, etc.) Translation movie

  4. Termination: Stop codons do not specify any amino acid Release factor protein binds to A site when stop codon is reached

  5. Termination: Hydrolysis occurs to break bond between final amino acid and its tRNA in the P position

  6. You are working at the Center for Disease Control (CDC), when the rest of your team gets sick with an influenza virus they have been studying. Your boss, Dr. Phillips, has given you the responsibility of figuring out which virus they have, because you are the only person on the team who is not sick. In your conversation with Dr. Phillips, she says, “Here is the situation. The team appears to have contracted an atypical flu virus. The symptoms are worse than usual and none of the team’s vaccinations protected them from this virus. We’re worried that we are dealing with a new strain of influenza we haven’t seen before. We need to figure out how this virus is different.” “I want you to compare the HA gene for the viruses the team was examining with a typical flu virus. I will get you the nucleotide sequence for a typical HA gene. You can start by finding the coding region for the gene.”

  7. Flu virus contains hemagglutinin (H) and neuraminidase (N)

  8. Hemagglutinin (HA) • A glycoprotein • An antigen that binds with host cell receptors to infect them

  9. Antibodies bind to antigens on viral membranes to prevent their activity • Binding is highly specific • Changes in antigen = antibodies no longer bind = no host cell protection Host cell receptor

  10. Influenza A virus: H and N can vary among species Flu vaccines typically contain H3N2, H1N1, and a B virus

  11. The types of antigens displayed on the surface of a flu virus are a component of the virus’ • Genotype • Phenotype

  12. Vaccines train your body to produce antibodies that “remember” the viral antigen…

  13. …as long as the antigen does not change! Antigenic drift, caused by mutation, is common in influenza viruses

  14. Changing the sequence of amino acids in a protein could change its function by • Altering the way the protein folds • Altering the way the protein interacts with other molecules • Changing the 3-D shape of the protein • All of the above

  15. ** 3’-ATCGGCAGGACCTTAAAT-5’5’-TAGCCGTCCTGGAATTTA-3’ If the DNA molecule above is a gene whose promoter lies to the right of this sequence on the screen, which RNA can be produced from this gene? • 3′-ATCGGCAGGACCTTAAAT-5′ • 5′-TAGCCGTCCTGGAATTTA-3′ • 3′-AUCGGCAGGACCUUAAAU-5′ • 5′-UAGCCGUCCUGGAAUUUA-3′ • Both A and B • Both C and D

  16. ** 5’CACGGUCGAUGAGGUUACAUAAC… 3’Part of an mRNA molecule is shown above. If this fragment came from the beginning of the mRNA, for which of the amino acid sequences below would it most likely code? • His-Gly-Arg • Thr-Val-Asp-Glu-Val-Thr • Met-Arg-Leu-His-Asn • Gln-Tyr-Ile-Gly-Val-Ala-Gly

  17. ** Dr. Phillips returned with a sheet of paper. “All I have been able to find so far is a partial sequence I believe is at the beginning of the HA gene.* I also found that the promoter for this gene is to the right of the sequence given here, and I have the start of the HA protein sequence. See if you can find the coding region while I look for more info.” DNA Sequence 3’CTTACATCGAGTTTCGTTACTATCAGAAGTACCAAT 5’ 5’GAATGTAGCTCAAAGCAATGATAGTCTTCATGGTTA 3’ HA amino acid sequence Met Lys Thr Ile Ile Ala Leu Ser Tyr Ile… 18

  18. In this case, the bottom strand is transcribed 3’CTTACATCGAGTTTCGTTACTATCAGAAGTACCAAT 5’ 5’GAATGTAGCTCAAAGCAATGATAGTCTTCATGGTTA 3’ DNA 3’CUUACAUCGAGUUUCGUUACUAUCAGAAGUACCAAU 5’ RNA

  19. 3’CTTACATCGAGTTTCGTTACTATCAGAAGTACCAAT 5’ 5’GAATGTAGCTCAAAGCAATGATAGTCTTCATGGTTA 3’ DNA 3’CUUACAUCGAGUUUCGUUACUAUCAGAAGUACCAAU 5’ RNA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’

  20. RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’ Reading frame-1 UAA CCA UGA AGA CUA UCA UUG CUU UGA GCU ACA UUC Reading frame-2 U AAC CAU GAA GAC UAU CAU UGC UUU GAG CUA CAU UC Reading frame-3 UA ACC AUG AAG ACU AUC AUU GCU UUG AGC UAC AUU C

  21. RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’ Reading frame-1 UAA CCA UGA AGA CUA UCA UUG CUU UGA GCU ACA UUC Reading frame-2 U AAC CAU GAA GAC UAU CAU UGC UUU GAG CUA CAU UC Reading frame-3 UA ACC AUG AAG ACU AUC AUU GCU UUG AGC UAC AUU C Met Lys Thr Ile Ile Ala Leu Ser Tyr Ile

  22. “Great! You found the start for the HA gene coding region. Here are HA genes the team had collected for the flu strains that they were studying. We only have information on the start of the gene, but it might be enough.” The virus that the team has contracted probably had a mutation that results in a different, but still functional version of the HA gene. See if one of the 4 strains of viruses the team was examining would fit this description.

  23. ** Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’ How is the HA protein produced by the new flu virus different from a typical flu virus? Strain #1 RNA5’UAACCAUGAGGACUAUCAUUGCUUUGAGCUACAUUC 3’ • There is no difference. • One amino acid has been changed. • Several amino acids have been changed. • The protein is too short. • The protein is too long.

  24. Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3 Lys Strain #1 RNA5’UAACCAUGAGGACUAUCAUUGCUUUGAGCUACAUUC 3’ Arg Mis-Sense (substitution) Mutation

  25. ** Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3 How is the HA protein produced by the new flu virus different from a typical flu virus? Strain #2 RNA5’UAACCAUGAAGACUAUCAUUGCUUAGAGCUACAUUC 3’ • There is no difference. • One amino acid has been changed. • Several amino acids have been changed. • The protein is too short. • The protein is too long.

  26. Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3 Leu Strain #2 RNA5’UAACCAUGAAGACUAUCAUUGCUUAGAGCUACAUUC 3’ Stop Non-Sense Mutation (truncation)

  27. ** Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3 How is the HA protein produced by the new flu virus different from a typical flu virus? Strain #3 RNA5’UAACCAUGAAGACCAUCAUUGCUUUGAGCUACAUUC 3’ • There is no difference. • One amino acid has been changed. • Several amino acids have been changed. • The protein is too short. • The protein is too long.

  28. Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3 Thr Strain #3 RNA5’UAACCAUGAAGACCAUCAUUGCUUUGAGCUACAUUC 3’ Thr Silent Mutation

  29. ** Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3 How is the HA protein produced by the new flu virus different from a typical flu virus? Strain #4 RNA5’UAACCAUGAAGACAUCAUUGCUUUGAGCUACAUUC 3’ • There is no difference. • One amino acid has been changed. • Several amino acids have been changed. • The protein is too short. • The protein is too long.

  30. Deletion of this U Typical HA RNA 5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3 Met Lys Thr Ile Ile Ala Leu Ser Tyr Ile Strain #4 RNA5’UAACCAUGAAGACAUCAUUGCUUUGAGCUACAUUC 3’ Met Lys Thr Ser Leu Leu STOP Frame Shift Mutation: alteration of reading frame

  31. Based on the information you have, which of the four strains is most likely to be the one causing the illness? • Strain 1 (mis-sense) • Strain 2 (non-sense) • Strain 3 (silent) • Strain 4 (frameshift) Be prepared to defend your answer!!!

  32. On your note card: • Name • Date • Explain, in terms of the central dogma, why you need to get a new flu shot every year. Explain your answer in terms of DNA, RNA, protein, antigen, etc.

More Related