What is the function of DNA?

1. What is the function of DNA?

2. Making proteins When genes are expressed, proteins are synthesized It involves two stages – transcription and translation

3. Learning Outcomes Explain the processes involved in transcription The different nucleic acid needed and its structure Explain the difference between primary and mature transcript

4. DNA recap .... answer these ... • An examples of? MY LOPER • Made up of? • Different types of bases? • Number of strands? • Held by? • What is the triplicate code?

5. DNA and RNA are polymers of nucleotides DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Nitrogenous base(A, G, C, or T) Sugar Phosphategroup Nucleotide Thymine (T) Sugar(deoxyribose) DNA nucleotide Polynucleotide Sugar-phosphate backbone

6. DNA has four kinds of bases, A, T, C, and G Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Pyrimidines Purines Figure 10.2B

7. DNA recap .... answer these ... • An examples of? Polymer • Made up of? Nucleotides (deoxyribose, phosphate and base) • Different types of bases? Arginine, Thymine, cytosine, guanine • Number of strands? 2 • Held by? Weak hydrogen bonds between strands, covalent bonds between nucleotides (deoxyribose 3’ and 5’) • Triplicate code? 3 bases code for an amino acid

8. RNA • RNA is ribonucleic acid. • It provides a bridge between DNA and protein synthesis. • Like DNA, RNA is also made up of nucleotides. What is a nucleotide? • However the nucleotides in RNA are slightly different! Spot the differences .....

11. different sugar (ribose – still pentose) • U (uracil) instead of T • Single strand, usually • RNA is also a nucleic acid Nitrogenous base(A, G, C, or U) Phosphategroup Uracil (U) Sugar(ribose)

12. RNA The three types of RNA are: • messenger RNA (mRNA) • ribosomal RNA (rRNA) • transfer RNA (tRNA) mRNA is: • Formed from the DNA in the nucleus. • Small enough to fit through the pores in the nuclear membrane.

13. mRNA comtinued .. • Found in the nucleus and cytoplasm. • A “bridge” molecule between DNA and protein. • Made by a process called transcription. • Made of thousands of bases in 3s called codons • Transcribe the mRNA, and split into codons.

14. mRNA comtinued .. • Found in the nucleus and cytoplasm. • A “bridge” molecule between DNA and protein. • Made by a process called transcription. • Made of thousands of bases in 3s called codons U G U A C U G U G C U G

15. rRNA • Make up ribosomes with proteins. • Made in nucleolus of nucleus and passed out into cytoplasm via the nuclear pores. • Remain as free ribosomes or attached to endoplasmic reticulum.

16. tRNA • Found only in the cytoplasm. • Only 3 bases exposed in 3D structure • General structure of “cloverleaf” • Made of two ends- • 1 is the anti-codon which binds to a specific mRNA codon. • 1 is the amino acid binding site.

17. tRNA • Specific to an amino acid. • Degenerative code (as more than one codon for an amino acid)

18. Amino acids – all similar structure with an amino group and a carboxyl acid group, “R” group changes

20. RNA SUMMARY 3 types; mRNA (messenger), rRNA (ribosomal) and tRNA (transfer) mRNA; carries a copy of the DNA code from the nucleus to the ribosome in the cytoplasm rRNA; formed at the ribosome alongside protein tRNA; carries an amino acid to the ribosome in the cytoplasm

21. Process to protein .... Gene 1 Gene 3 DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Amino acid

22. Transcription • Watch these videos and place the statements in order .... Higher education Scotland Crash course 2.21-7.04. McGraw Hill DNALC

23. Transcription produces genetic messages in the form of mRNA RNA nucleotide RNApolymerase 3’ 5’ 3’ Direction oftranscription 5’ Templatestrand of DNA Newly made RNA

24. DNA vs RNA Compare the 2 nucleic acid types.

25. RNA vs. DNA • RNA contains the sugar ribose; DNA contains deoxyribose. • RNA contains the base uracil; DNA contains thymine instead. • RNA is usually single stranded; DNA is usually double stranded. • RNA is short: one gene long at most; DNA is long, containing many genes.

26. RNA vs. DNA

27. RNA • Complete the following table to compare RNA and DNA 1 2 Nucleus & cytoplasm Nucleus only ribose deoxyribose G, C, A & URACIL G, C, A & T 3 1 Short Long

28. Transcription Test A T G G G C A T A C T A C C C G T A T G • How many bases in the genetic code correspond with an amino acid? • Draw the section of the mRNA strand that would be transcribed from section X on the DNA shown. • Which enzyme would direct this process? • What is the difference between an intron and an exon? • What happens to primary transcript of mRNA? • What is the name of this process?

29. Transcription Test U A C C C G U A U G • 3, triplicate code • Top one, 3’ to 5’ • RNA polymerase • Exon is expressed as it is the coding region, intron is non-coding region – polypeptide is fragmented • From primary transcript Introns are removed and exons are spliced together to form mature mRNA • RNA splicing

30. Remember RNA? or ID badges • How many types? • Location? • What are each of their structures (and label within) and functions? • Any specific names gives? Lengths?

31. Remembering RNA ... http://www.mfpl.ac.at/rna-biology/rna-history/

32. RNA

33. Learning Outcomes Gene 1 Gene 3 DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Amino acid Review the process of transcription Describe the process of translation

34. Translation • Site E; releases (discharges) tRNA after amino acid (aa) part of polypeptide • Site P – next tRNA held by H bond to mRNA • Site A – holds next tRNA with its aa then peptide linked to previous aa (P) 5’ 3’ Occurs in cytoplasm (mature mRNA transcript through nuclear pore) on the ribosome (enzymes needed for protein synthesis).

35. Translation .....

36. Translation Occurs in cytoplasm (mature mRNA transcript through nuclear pore) on the ribosome.

37. 1. A ribosome attaches to the mRNA at an initiation codon (AUG). The ribosome encloses two codons. 3.The next amino acid-tRNA attaches to the adjacent mRNA codon (leu in this case) - The codon and anticodon bases matching up Translation 2. met-tRNA diffuses to the ribosome and attaches to the mRNA initiation codon by complementary base pairing

38. 4. The bond between the amino acid and the tRNA is cut and a peptide bond is formed between the two amino acids. 5 The ribosome moves along one codon so that a new amino acid-tRNA can attach. The free tRNA molecule leaves to collect another amino acid. The cycle repeats from step 6. The polypeptide chain elongates one amino acid at a time, and peels away from the ribosome, folding up into a protein as it goes. This continues for hundreds of amino acids until a stop codon is reached, when the ribosome falls apart, releasing the finished protein.

39. Steps in translation SUMMARY A stop codon (AUU, AUC or UGA) which has a release factor which frees the polypeptide from ribosome. • Initiation – needs start codon (AUG, for methionine) in P site with anti codon? • Elongation – complementary tRNA bring correct amino acids which are added through a peptide bond • Termination

40. Translation Multiple translation can occur with many ribosomes reading the same mRNA – the ribosomes on the same mRNA are called - polysomes or polyribosome Translation requires ATP!

41. What’s happening?

42. Now explain the WHOLE process protein synthesis

43. Animate/Model/Demonstrate Can you animate it? Anyway possible – here is my original ......