Topic: DNA Transcription and Translation Aim: How are proteins made from DNA?

DNA RNA Amino Acids(Proteins) DNA contains the genetic information to make amino acids Amino acids combine to make proteins These proteins determine the physical traits of an organism and control cellular functions. Proteins do everything, and DNA gets all the credit! Think of them as tiny minions who do all the work

RNA vs DNA RNA: ribonucleic acid Carries out protein synthesis Differences from DNA: different sugar (ribose) single strand different base no thymine URACIL instead

DNA and Protein Synthesis

3 Types of RNA: Messenger RNA: (mRNA) carries nucleotide sequence from nucleus to ribosome Transfer RNA: (tRNA) picks up amino acid in cytoplasm and carries them to ribosome Ribosomal RNA: (rRNA)found in ribosome, joins mRNA and tRNA; forms protein

Steps of Transcription Transcription- process that makes mRNA from DNA DNA unzips into 2 separate strands A. DNA Helicase is the enzyme that breaks H-bond 2. Free floating RNA NITROGEN BASES in the nucleus pair up w/unzipped DNA NITROGEN BASES: A. Cytosine(C) pairs with Guanine(G) * (G) with (C) B. Uracil(U) pairs with Adenine(A) * (A) with (U) C. Thymine (T) pairs with Adenine (A) ***remember (T) is only with DNA

3. After all the pairing is done: a single strand of RNA has been produced. 4. Genetic code from DNA is transferred to mRNA 5. The code obtained from DNA lets the mRNA know which amino acids to pick up: code is a set of 3 nitrogen bases = Codon

Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA

DNA G A T T A C A C U A A U G U mRNA DNA RNA Practice making mRNA using the DNA template DNA G A T T A C A Remember: RNA does not have T(Thymine); it’s replaced by U(Uracil) C U A A U G U mRNA

Transcription Practice Transcript the following segment of DNA into RNA DNA: A U G T T T A G A C A T G G C RNA:

Translation Conversion of RNA into amino acid sequence that makes a protein The mRNA leaves the nucleus and enters the cytoplasm Ribosomes attach to mRNA tRNA (carrying anti-codon) picks up the correct amino acids and carries them to the mRNA strand forming the protein Ex: tRNA carries GAU (anti-codon)& looks for CUA on mRNA

DNA and Protein Synthesis Codon: three bases code for a specific protein: ex: AAA = Lysine The codons code for 20 amino acids Just like the alphabet has 26 letters to make all the words we know, the 20 amino acids make all the different proteins found in living organisms The codons are the template for protein synthesis, which takes place on the ribosomes (rRNA) in the cytoplasm

Translation: changing mRNA into Amino Acids (Proteins) Amino acids are linked together in the same order as the codons , creating a protein chain Just like linking letters to make words, linking amino acids makes proteins mRNA CUA AUG UGC Leucine methionine Amino Acid Amino Acid Amino Acid

DNA and Protein Synthesis - Summary

Translation mRNA tRNA mRNA Nucleus Lysine Phenylalanine Methionine Ribosome mRNA Start codon

Translation (continued) Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA mRNA Ribosome Translation direction

Summary of transcription and translation DNA Stage mRNA is transcribed from a DNA template. 1 mRNA RNA polymerase Amino acid TRANSLATION Stage Each amino acid attaches to its proper tRNA with the help of a specific enzyme and ATP. 2 Enzyme tRNA Initiator tRNA Anticodon Stage Initiation of polypeptide synthesis 3 Large ribosomal subunit The mRNA, the first tRNA, and the ribosomal subunits come together. Start Codon Small ribosomal subunit mRNA Figure 10.15

New peptide bond forming Growing polypeptide Stage Elongation 4 A succession of tRNAs add their amino acids to the polypeptide chain as the mRNA is moved through the ribosome, one codon at a time. Codons mRNA Polypeptide Stage Termination 5 The ribosome recognizes a stop codon. The poly-peptide is terminated and released. Stop Codon Figure 10.15 (continued)

Lesson Summary Transcription: changing DNA into RNA How to change DNA into RNA? Answer: Just follow Chargaff’s Rule: A always pair with T C always pair with G However, RNA does not have T(Thymine), it has U(Uracil)

Translation: changing mRNA into amino acids (proteins) How to change mRNA into amino acids? Answer: Step 1: remember, 3 bases equal 1 codon Step 2: look at the universal amino acids chart to translate into the correct amino acids.