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Chapter 11

Chapter 11. Section 2-DNA to Protein. I) Genes and Proteins. sequence of nucleotides in DNA contain info  which leads to the construction of proteins proteins fold into complex 3-D shapes  key structures in regulation of cell fxns enzymes in regulation of chemical rxns:

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Chapter 11

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  1. Chapter 11 Section 2-DNA to Protein

  2. I) Genes and Proteins • sequence of nucleotides in DNA contain info  which leads to the construction of proteins • proteins fold into complex 3-D shapes key structures in regulation of cell fxns • enzymes in regulation of chemical rxns: • cellular respiration-breaking down glucose molecules • digesting food • making spindle fibers in mitosis

  3. I) Genes and Proteins • remember that enzymes ctrl all chemical rxns of an org • so b/c DNA holds the code for proteins in ctrls all the fxns that the proteins regulate  DNA ctrls cells • Remember that: • DNA sequence (made up of sequence of nucleotides)  single strand of RNA sequence  RNA single strand sequence string of amino acids that create a single protein

  4. II) RNA • 3 ways that RNA structure differs from DNA structure: • Uracil replaces Thymine and base pairs with Adenine. • The role of RNA in cell: • DNA provides instructions for making proteins • A.A. are the parts that make up the protein

  5. The role of RNA in cell: DNA provides instructions for making proteins A.A. are the parts that make up the protein Protein synthesis is done by RNA molecules 3 types of RNA: Messenger RNA (mRNA)-brings instructions from DNA in the nucleus to the cytoplasm Ribosomal RNA (rRNA)-found in the ribosome binds to mRNA & uses instructions to assemble A.A. in the correct order Transfer RNA (tRNA)-this is the supplier RNA, delivers A.A. to ribosome to be assembled into a protein II) RNA

  6. mRNA carries information through nuclear envelope to ribosome to make proteins How transcription works? In nucleus-enzymes unzips DNA strands in the region that will be transcribed Free RNA nucleotides form base pairs with their complementary nucleotides on the DNA strand-mRNA is finished when RNA nucleotides bond together mRNA strand breaks away & the DNA strands rejoin mRNA strand goes through RNA processing & then leaves the nucleus to enter the cytoplasm Transcription

  7. Introns-def-pg291- long noncoding nucleotide sequences (intervening regions) within a gene Exons-def-pg291-regions of coding nucleotide sequences that contain information to be expressed within a gene How RNA processing works? When mRNA is transcribed both introns & exons are copied Before mRNA leaves the nucleus-introns are cut out Enzymes cut out introns, then paste the exons together to make new mRNA New mRNA then leaves the nucleus for the cytoplasm RNA Processing

  8. The nucleotide sequence transcribed from DNA to messenger RNA acts as a genetic message  the complete information for the building of a protein Proteins are made up of chains of A.A. 20 common Amino Acids How does mRNA with 4 bases form a code for 20 different Amino Acids? Codons-def-pg292-a group of 3 nitrogenous bases in mRNA that code for 1 A.A. Example: Refer to Table 11.1-pg292 UUU = Phenylalanine CUU = ??? CCU = ??? 64 possible sequences when 3 bases are used for codons The Genetic Code

  9. Some codons don’t code for A.A.: Ex/ AUG = Start codon/Methionine Ex/ UAA/UAG/UGA = Stop codon One codon can code for the same A.A., but for any one codon there is only 1 A.A. All organisms use same genetic code  life on Earth came from common ancestor The Genetic Code

  10. Translation: From mRNA to Protein • Translation-def-pg.293-the process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of A.A. in protein • Where does translation take place?

  11. Role of transfer RNA (tRNA) is to bring the dissolved A.A. in the cytoplasm to the ribosomes. Structure of tRNA: The role of transfer RNA

  12. Each tRNA attached to only one type of A.A. Translating mRNA correctly depends on the on matching of tRNA anticodon to mRNA codon How tRNA works? Each tRNA anticodon matches a specific codon found on the mRNA transcript that is moving through the ribosome Ex/ mRNA codon AUG (start) tRNA Anticodon- UAC (start) The role of transfer RNA

  13. How it works? mRNA leaves the nucleus after it has been processed mRNA then enters the cytoplasm and heads for ribosome. mRNA is read by ribosome based on the mRNA codon, ribosomes will get a tRNA with a complementary anticodon at one end & an attached A.A. at the other tRNA attached to the ribosome and the mRNA at the anticodon another tRNA attaches to the ribosome and the mRNA at the next anticodon and a peptide bonds is formed between the 2 A.A. the tRNA that attached first will now move on to picking up another A.A. this continues open until the STOP codon is in place  translation ends and the A.A. strand is released from the ribosomes A.A. chains become proteins, when freed and they twist into 3-D shapes Translating the mRNA code

  14. Translating the mRNA code

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