Transcription and the Genetic Code

Today’s Agenda Notes: Transcription

Different Organisms in Nature

Bellwork Is the structure of DNA different in different organisms? Does the code in DNA represent the same thing in all organisms? What makes these organisms different?

Objectives Explain the distinguishing characteristics of DNA and RNA Describe how mRNA is synthesized Explain how the code found in DNA encodes for amino acids

Key Terminology RNA Messenger RNA Ribosomal RNA Transfer RNA RNA polymerase Promoter Codon Genetic code

RNA Polymer of nucleotides Like DNA composed of 5 carbon sugar, phosphate group and a nitrogenous base Unlike DNA Ribose sugar (rather than deoxyribose) Uses the base uracil (rather than thymine) all other bases the same as DNA Single stranded (rather than double stranded)

Different types of RNA mRNA (messenger RNA) rRNA (ribosomal RNA) takes information from DNA in the nucleus to the ribosomes in the cytoplasm rRNA (ribosomal RNA) makeup ribosomes along with protein ribosomes synthesizes protein tRNA (transfer RNA) carries amino acids to ribosomes reads the bases on the mRNA

Transcription Process of producing an RNA molecule based on the sequence of the DNA template

RNA Polymerases separates the two strands of the double helix Enzyme involved in the synthesis of RNA RNA polymerase binds to the DNA separates the two strands of the double helix “unzips” the DNA Uses one strand of the DNA as the template for the synthesis of RNA

mRNA Sequence made is complementary to the DNA sequence DNA contain mRNA contains Guanine (G) Cytosine (C) Thymine (T) Adenine (A) Uracil (U) Property of CTE Joint Venture 11/20/2018

PROPERTY OF PIMA COUNTY JTED, 2010 Think-Pair-Share What is the complementary mRNA sequence for the following DNA sequence? DNA: TAC TTG GGC TCC CTT CTG GGG RNA: _________________________________ 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class PROPERTY OF PIMA COUNTY JTED, 2010 3

Cellular Location of Transcription Eukaryotes Occurs in nucleus After mRNA made it must be processed before transported to cytoplasm Prokaryotes Occurs in cytoplasm Property of CTE Joint Venture 11/20/2018

Process of Transcription Involves three steps: RNA polymerase binding and initiation Elongation of mRNA Termination

Initiation RNA polymerase binds to promoter Promoter a specific DNA base sequence that indicates the binding site for RNA polymerase RNA polymerase binds initiates the unwinding of DNA

Elongation RNA polymerase begins attaching nucleotides to the newly synthesized RNA

Termination RNA polymerase reaches termination site transcription ceases Most common termination sequence AAUAAA

Ribosomes Once mRNA is made and in the cytoplasm the ribosomes attach they decode the mRNA 3 nucleotides at a time Each group of three nucleotides = a codon code for an amino acid that make up the polypeptide chain Property of CTE Joint Venture 11/20/2018

Genetic Code Table Property of CTE Joint Venture 11/20/2018

PROPERTY OF PIMA COUNTY JTED, 2010 Think-Pair-Share Identify the amino acid for each of the codons CAG AAU UUG AUG (start codon) UAG 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class PROPERTY OF PIMA COUNTY JTED, 2010 3

Answer to Practice Problem CAG = Glutamine AAU = Asparagine UUG = Leucine AUG (start codon) = Methionine UAG = Stop Codon Property of CTE Joint Venture 11/20/2018

Properties of the Genetic Code Genetic code redundant most amino acids have more than one codon Unambiguous each codon has only one meaning Code has start and stop signals Universal used by all living things

PROPERTY OF PIMA COUNTY JTED, 2010 Think-Pair-Share How does the universal genetic code relate to evolution? 3. Think-pair-share teacher presents a question teacher gives wait time for student to form answer teacher instructs students to share their answer with a partner teacher calls on non-volunteers to share with the class PROPERTY OF PIMA COUNTY JTED, 2010 3

PROPERTY OF PIMA COUNTY JTED, 2010 Minute Paper You have two minutes to write down two key points of today’s lesson. Be prepared to share. 29. Minute paper or Quick Write teacher provides a prompt from the lesson students have one minute to write down a summary of the key points students compare with a partner teacher uses a strategy to check all PROPERTY OF PIMA COUNTY JTED, 2010 24