1. RNA STRUCTURE TYPES OF RNA TRANSCRIPTION

2. Learning Targets Students will be able to compare and contrast DNA and RNA Students will be able to identify the job of RNA

3. Structure of RNA  Single-stranded polymer made of repeating nucleotides  RNA = Ribonucleic Acid  Contains a phosphate group  Contains a RIBOSE sugar (instead of deoxyribose!) – has an oxygen  Contains nitrogen bases…C, A, G and U!  RNA has URACIL instead of thymine!!!!

4. How does RNA compare to DNA?

5. 3 Types of RNA 1. Messenger RNA (mRNA) – “records” information from the DNA in the nucleus and transports it out of the nucleus to the ribosomes

6. 3 Types of RNA 2. Transfer RNA (tRNA) - deliver amino acids one by one to protein chains forming at ribosomes 3. Ribosomal RNA (rRNA) – found in the ribosomes; helps with ribosome’s structure, although the function is not completely understood

7. Why is RNA important?  Because it is involved with protein synthesis!  DNA risks being damaged if it leaves the nucleus, so mRNA copies the info from the DNA to bring it out to the ribosomes and tRNA helps to bring the amino acids to the ribosome to form the protein strands

8. How do we get mRNA from DNA?  A process called TRANSCRIPTION  4 steps similar to DNA replication, but with a different end result What do you notice is different from DNA replication? Only 1 single strand is produced!

9. Transcription  Step 1 – DNA gets “unzipped” - helicase  Step 2 – RNA polymerase guides RNA nucleotides to line up in the proper order by hydrogen-bonding to their complementary bases on one side of DNA

10. Transcription  Step 3 – Covalent bonds form along the sugars & phosphates to hold the mRNA together  Step 4 - transcription continues until a “stop sign” is reached and the mRNA strand is complete  Transcription Animation Transcription Animation

11. The Genetic Code  Each set of 3 nitrogen bases represents 1 amino acid = CODON  64 possible codons  3 code “stop”  61 code for amino acids (20 different a.a.)  1 codes to “start” – AUG = methionine  Code is UNIVERSAL – codons represent the same amino acids in all organisms

14.  1. How many different codons code for valine? 44  2. The codon CGU is for which amino acid?  Arginine  3. What are the codons for the three “stops”?  UAA, UAG, UGA  4. What are the first 3 amino acids for this strand of mRNA?  Alanine, Threonine, Glutamic acid Use your codon chart to answer the following: