RNA & PROTEIN SYNTHESIS

1. RNA & PROTEIN SYNTHESIS SC STANDARD B-4 STUDENTS WILL DEMONSTRATE AN UNDERSTANDING OF THE MOLECULAR BASIS OF HEREDITY

2. Topic: Protein Synthesis • EQ: HOW WOULD YOU COMPARE TRANSCRIPTION &TRANSLATION? • Notebook: page 98

3. GENES: • are coded DNA instructions that control the production of proteins within a cell.

4. RNA (Ribonucleic Acid) • single stranded nucleic acid • 5-carbon sugar is ribose • Phosphate group • 1 of 4 nitrogenous bases: • 1. adenine 2. guanine • 3. cytosine 4. uracil

5. Types of RNA • 1. Messenger RNA (mRNA) • carries copies of instructions for assembling proteins from the gene (in nucleus)  ribosomes (in cytoplasm or RER)

6. mRNA • single strand of nucleotides • read in groups of 3 called codons • look at the 2 codons on this slide: What sequence of nucleotides on DNA did this segment of mRNA come from?

7. Ribosomal RNA : rRNA • with proteins make up ribosomes • ribosomes made of 2 subunits: 30S and 50S

8. Transfer RNA: tRNA • transfers each of the amino acids to the ribosome as is specified by the code in mRNA • one end has the anticodon • other end the a.a.

9. anticodon: group of 3 bases that are complimentary to the codon on mRNA

10. PROTEIN SYNTHESIS TRANSCRIPTION TRANSLATION • INVOLVES TRANSCRIBING (copying) THE CODE IN DNA MAKING mRNA • INVOLVES TRANSLATING the CODE into AMINO ACIDS  POLYPEPTIDE CHAINS  PROTEINS • mRNA, tRNA, rRNA

11. TRANSCRIPTION • mRNA molecules are made by copying part of a nucleotide sequence of DNA into a complimentary (C’) sequence in mRNA • Steps: • 1. RNA Polymerase opens DNA • 2.RNA Polymerase uses 1 of the DNA strands as template • uses C’ base pair rules

12. Transcription • RNA Polymerase binds to DNA at certain points called “promoters”

13. Transcription • after unwinding a short portion of the double helix, RNA Polymerase moves along 1 of the DNA strands making a strand of RNA using base-pair rules except there is no T in RNA: A is paired with U (Uracil)

15. Transcription

16. Transcription • RNA Polymerase moves along the DNA until it hits a signal to stop. • this strand of RNA is called pre-mRNA

17. RNA Editing • portions of DNA called introns do not code for proteins • DNA portions that code for proteins called exons. • introns get cut out of pre-mRNA and the exons get spliced together • http://www.dnalc.org/view/16938-3D-Animation-of-RNA-Splicing.html

19. Transcription Animations • http://www.johnkyrk.com/DNAtranscription.html

20. The Genetic Code • is the “language” of the mRNA instructions • written in a language that only has 4 “letters”: • G, C, A, & U • must code for 20 amino acids • is read 3 letters at a time • every 3 consecutive letters codes for 1 of the 20 a.a., a start signal, or a stop

21. The Genetic Code

22. The Genetic Code • codon: is a “word” in the code • consists of 3 consecutive nucleotides that specify an a.a., a stop, or a start

23. The Genetic Code • Page of Notebook: • “Crack the Code” • Quick Lab from page 303 of textbook

24. TRANSLATION • cell uses information from mRNA to produce proteins

25. Translation Step 1 Step 2 • mRNA attaches to ribosome • 1stcodon codes for methionine • tRNA with anticodon complimentary to codon in mRNA attaches to ribosome, delivering correct a.a.

26. Translation Step 3 Step 4 • peptide bond forms between a.a brought to ribosome by 1st & 2ndtRNA • ribosome only holds 2 tRNA so 1st one leaves ribosome as 3rd one “docks” • Process repeated until “stop” codon

27. Translation Step 5 Animation • polypeptide chain falls off ribosome • Ribosome free to start another peptide chain • http://www.wisc-online.com/Objects/ViewObject.aspx?ID=AP1302

28. PROTEIN SYNTHESIS TRANSCRIPTION TRANSLATION • DNA  mRNA • nucleus • mRNA  cytoplasm or RER • mRNA + ribosome + tRNA  protein

29. Quick Lab • Handout: Genetic Code for Keratin • Page of Notebook • Answer questions 1-4