1. Chapter 13 – RNA & Protein Synthesis MS. LUACES HONORS BIOLOGY

2. 13.1 RNA  RNA also consists of a long chain of nucleotides, but it puts the genetic code into action  Uses DNA to translate instructions and direct production of proteins  Some important differences between DNA & RNA:  The sugar in RNA is ribose instead of deoxyribose  Single-stranded instead of double-stranded  Contains uracil in place of thymine

3. 13.1 RNA  DNA is the master plan, while RNA is the copied blueprint – contains only the instructions needed to build a certain area (protein)

4. 13.1 RNA  Functions and types of RNA:  Messenger RNA (mRNA): carries copies of instructions from DNA to other parts of the cell  Ribosomal RNA (rRNA): make up ribosome molecules where protein is made  Transfer RNA (tRNA): transfers amino acids to ribosome to build the protein

5. 13.1 RNA  Transcription: segments of DNA serve as templates to produce complementary RNA molecules (translate DNA)  Happens in the nucleus of eukaryotic cells  Requires enzyme RNA Polymerase which binds to DNA and separates the strands, then translates one of the strands by adding complementary bases

6. 13.1 RNA  How does it know where to start or stop transcription?  Promoters (regions of DNA with specific base sequences) signal RNA Polymerase exactly where to start making RNA  Stop areas signal RNA Polymerase transcription is finished

7. 13.1 RNA  Once transcription has finished, editing has to be made to the pre-mRNA molecule to get rid of introns (junk DNA)  Portions that are not junk are called exons – these are put back together and exit the nucleus into the cytoplasm to find a ribosome and begin making the protein

8. 13.2 Ribosomes & Protein Synthesis  The genetic code is read 3 “letters” at a time, so that each “word” is 3 bases long and corresponds to a single amino acid  “Letters” are the bases of RNA – A, G, C, U  “Words” are codons – ex: AGU, CAU, GGC which code for amino acids. Amino acids (there are 20) that are joined together into long chains (polypeptides) make proteins.

9. 13.2 Ribosomes & Protein Synthesis  There are 64 possible 3-base codons in the genetic code, in which some amino acids are specified by more than one codon  Ex: Tryptophan is only coded by UGG, but Tyrosine can be coded by UAU or UAC  The properties of the protein depend on the order of amino acids, which determines the shape and function

10. 13.2 Ribosomes & Protein Synthesis  How do we know when to start or stop translation?  There are start (AUG) and stop (3 different ones) codons at the beginning and end of the mRNA molecule being translated

11. 13.2 Ribosomes & Protein Synthesis  Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains. This decoding process is known as translation  Once the polypeptide is complete, it will fold into its final shape or join with other polypeptides to become a functional protein

12. 13.2 Ribosomes & Protein Synthesis

13.  Steps in Translation:  1. In the cytoplasm, the ribosome attaches to an mRNA molecule  2. Each codon is read, and sends for a tRNA molecule with an anticodon (complementary base) to retrieve the amino acid  3. The tRNA molecule binds to the ribosome, adding the amino acid through peptide bonds into a polypeptide chain that continues to grow  4. When the STOP codon is reached, the ribosome releases both the newly formed polypeptide and the mRNA molecule. Translation is complete.

14. 13.2 Ribosomes & Protein Synthesis  All 3 types of RNA are involved in translation  Surprisingly, most organisms share the same genetic code, and therefore, the same codon reading and amino acids!!  Why we can make bacteria make our insulin  The central dogma of molecular biology is that information is transferred from DNA  RNA  Protein  Many proteins are enzymes that carry out functions in our bodies  Sometimes, the dogma can be reversed: HIV has RNA that becomes DNA in human immune cells

15.  https://www.youtube.com/watch?v=h3b9ArupXZg https://www.youtube.com/watch?v=h3b9ArupXZg  https://www.youtube.com/watch?v=6gUY5NoX1Lk https://www.youtube.com/watch?v=6gUY5NoX1Lk