Transcription and Translation

1. Transcription and Translation Essential Standard 3.1.2 Explain how DNA and RNA code for proteins and determine traits.

2. RNA is…. • A nucleic acid • Made of nucleotides • Single stranded • Located in the nucleus AND the cytoplasm

3. General RNA Structure • RNA is made of nucleotides. • Sugar = ribose • Phosphate • Bases = Adenine, Cytosine, Guanine and Uracil • RNA is single stranded. • The sugar and phosphate groups alternate to make up the “backbone”. • The bases attach to the sugar

5. Types of RNA • There are three different types of RNA. They are: • Messenger RNA (mRNA) • Transfer RNA (tRNA) • Ribosomal RNA (rRNA)

6. Messenger RNA • mRNA has the responsibility of carrying the “message” from the DNA to the ribosomes for protein synthesis.

7. Transfer RNA • The job of tRNA is to locate the correct amino acid in the cytoplasm and then transfer that amino acid to the ribosome during translation.

8. Ribosomal RNA • This is a single strand of RNA that “jumbles” up on itself and forms the ribosome. • It is the “workbench” for protein synthesis. (mRNA will stretch across it during translation.)

9. Comparison of RNA and DNA DNA RNA Contains the sugar ribose Made up of one strand Has the bases A, G, C and U. • Contains the sugar deoxyribose • Made up of two strands • Has the bases A, G, C and T.

11. Transcription

12. Transcription is….. • The process by which DNA is used as a template to make RNA.

13. Where does transcription happen? • Transcription occurs in the nucleus. • Why? DNA can NOT leave the nucleus!!!

14. Why does transcription happen? RNA is needed for protein synthesis to occur. • The mRNA carries the “message” for protein synthesis. • The tRNA is going to bring in the amino acids needed to make the proteins. • The rRNA is what the ribosomes are made of. Translation (protein synthesis) occurs on the ribosome.

15. How does transcription happen? 1. The section of DNA that needs to be transcribed is untwisted and unzipped.

16. How does transcription occur? • An enzyme brings in complementary RNA nucleotides. • A’s bond with U’s • T’s bond with A’s • C’s bond with G’s • G’s bond with C’s

17. How does transcription occur? • This RNA is released from the DNA and the DNA goes back to the original structure.

18. How does translation occur? • The RNA is now called “pre _ RNA”. It must be edited before it is released into the cytoplasm.

19. A Summary Transcription Animation

20. Translation

21. Where does translation happen? • Translation happens on a ribosome.

22. Why does translation happen? • Translation happens so that proteins can be made from the message sent in the form of mRNA.

23. Translation “players” • mRNA • tRNA • rRNA • Amino acids

24. How translation happens • mRNA, tRNA that has the first amino acid and the two ribosomal subunits join together. This forms a translation initiation complex. • This starts at the start codon, AUG. • The first amino acid will be Methione.

26. How translation happens • Amino acids are brought in one at a time. • tRNA with next amino acid is brought into the A site. • Peptide bond is formed between the amino acids on the tRNAs at the A and P sites. • Ribosomal unit shifts toward the E site. The 1sttRNA is at the E site, 2ndtRNA is at the P site and the A site is now empty.

28. How translation happens • The tRNA at the E site leaves to find another amino acid. • Elongation continues until a stop codon on the mRNA is reached.

29. How translation happens • A stop codon is reached. (UAA, UAG or UGA) • A protein called a release factor binds to the stop codon and the polypeptide is freed from the ribosome

32. What happens next? • Proteins are sent to the Golgi Body for modification so that they can become functional.

33. Summary

34. Summary of Translation Translation Animation