THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN

I Can… Describe the locations, reactants, and products of transcription and translation. Diagram the overall process of transcription and translation.

DNA  Proteins  Cells DNA (genes) has the information to build proteins proteins cells DNA gets all the glory, Proteins do all the work 3

How do proteins do all the work proteins run living organisms enzymes control all chemical reactions in living organisms structure all living organisms are built out of proteins 4

Protein Synthesis: overview The sequence of DNA determines the sequence of Amino Acids (monomer) that makes up each protein (polymer). Transcription: synthesis of mRNA under the direction of DNA Translation: actual synthesis of a polypeptide under the direction of mRNA

The Triplet Code The genetic instructions for a protein/ polypeptide chain are ‘written’ in the DNA as a series of 3-nucleotide ‘words’ called…. Codons: the basic unit of genetic code Don’t forget! ‘U’ (uracil) replaces ‘T’ in RNA

Transcription: Transcription of a gene occurs in three main steps: Initiation, involving the attachment of RNA polymerase to the promoter and the start of RNA synthesis, Elongation, as the newly formed mRNA strand grows Termination, when RNA polymerase reaches the terminator DNA and the polymerase molecule detaches from the newly made mRNA strand and the gene.

Transcription: overview

10.10 Eukaryotic RNA is processed before leaving the nucleus as mRNA Eukaryotic mRNA undergoes processing before leaving the nucleus. RNA splicing removes introns (intervening sequences) and joins exons (expressed sequences) to produce a continuous coding sequence. Student Misconceptions and Concerns • Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. Teaching Tips • Many analogies can be developed to represent the selective expression of a gene requiring the deletion of introns. Instructors who only assign some modules of a chapter are treating the chapters like sections of exons and introns, portions to be read and portions to be skipped. Alternately, students who highlight a chapter might be thought of as editing the book into exons, portions to be reviewed, and introns, nonhighlighted sections that will not be studied. Both analogies are imperfect, but may still convey the concept of selective reading. Active Lecture Tips  See the Media Review: “Learn.Genetics” Genetic Science Learning from the University of Utah on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Baking Cookies Describes the Central Dogma on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Using a Food Analogy to Think About Protein Synthesis on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Students Perform a Protein Synthesis Play on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 9

Translation mRNA from nucleus is ‘read’ along its codons by tRNA’s anticodons at the ribosome Each codon on the mRNA has a complimentary tRNA anticodon (nucleotide triplet) Each tRNA has been previously linked to an amino acid.

Translation continued Ribosome: site of mRNA codon & tRNA anticodon coupling P site: holds the tRNA carrying the growing polypeptide chain A site: holds the tRNA carrying the next amino acid to be added to the chain

Translation continued Initiation: union of mRNA & tRNA Elongation: codon recognition peptide bond formation Translocation Termination: ‘stop’ codon reaches ‘A’ site

Translation

DNA Transcription RNA Codon Translation Polypeptide Amino acid Figure 10.7-1 DNA A A A C C G G C A A A A Transcription RNA U U U G G C C G U U U U Codon Translation Figure 10.7-1 Transcription and translation of codons (partial) Polypeptide Amino acid 15

Second base of RNA codon U C A G Figure 10.8a Second base of RNA codon U C A G UUU UCU UAU UGU U C A G Phe Tyr Cys UUC UCC UAC UGC U Ser UUA UCA UAA Stop UGA Stop Leu UUG UCG UAG Stop UGG Trp CUU CCU CAU CGU U C A G His CUC CCC CAC CGC C Leu Pro Arg CUA CCA CAA CGA Gln First base of RNA codon Third base of RNA codon CUG CCG CAG CGG AUU ACU AAU AGU U C A G Ser Asn AUC lle ACC AAC AGC A Thr Figure 10.8a The genetic code used to translate RNA codons to amino acids AUA ACA AAA AGA Arg Lys AUG Met or start ACG AAG AGG GUU GCU GAU GGU U C A G Asp GUC GCC GAC GGC G Val Ala Gly GUA GCA GAA GGA Glu GUG GCG GAG GGG 16

Strand to be transcribed Figure 10.8b-1 Strand to be transcribed T A C T T C A A A A T C DNA A T G A A G T T T T A G Figure 10.8b-1 Deciphering the genetic information in DNA (step 1) 17

Strand to be transcribed Figure 10.8b-3 Strand to be transcribed T A C T T C A A A A T C DNA A T G A A G T T T T A G Transcription RNA A U G A A G U U U U A G Figure 10.8b-3 Deciphering the genetic information in DNA (step 3) Start codon Stop codon Translation Polypeptide Met Lys Phe 18

10.8 The genetic code dictates how codons are translated into amino acids The genetic code is nearly universal, in that the genetic code is shared by organisms from the simplest bacteria to the most complex plants and animals. Student Misconceptions and Concerns • Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. Teaching Tips • You may want to note the parallel between the discovery in 1799 of the Rosetta Stone, which provided the key that enabled scholars to crack the previously indecipherable hieroglyphic code, and the cracking of the genetic code in 1961. Consider challenging your students to explain what part of the genetic code is similar to the Rosetta Stone. This could be a short in-class activity for small groups. • The authors note the universal use of the genetic code in all forms of life. The evolutionary significance of this fundamental, universal language is a reminder of the shared ancestry of all life. The universal genetic code is part of the overwhelming evidence for evolution. Active Lecture Tips  See the Media Review: “Learn.Genetics” Genetic Science Learning from the University of Utah on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Baking Cookies Describes the Central Dogma on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Using a Food Analogy to Think About Protein Synthesis on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Students Perform a Protein Synthesis Play on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 19

Figure 10.15-5 A summary of transcription and translation (step 5) DNA Transcription NUCLEUS mRNA 1 Transcription RNA polymerase Translation CYTOPLASM Amino acid Amino acid attachment 2 Enzyme tRNA ATP Initiator tRNA Anticodon Large ribosomal subunit Initiation of polypeptide synthesis 3 U A C A U G Start codon Small ribosomal subunit mRNA New peptide bond forming Growing polypeptide Elongation Figure 10.15-5 A summary of transcription and translation (step 5) 4 Codons mRNA Polypeptide 5 Termination Stop codon 20

Review of Transcription and Translation

I Can… Describe the major types of mutations, causes of mutations, and potential consequences.

10.16 Mutations can affect genes A mutation is any change in the nucleotide sequence of DNA. Mutations can involve large chromosomal regions or just a single nucleotide pair. Student Misconceptions and Concerns • Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. • Mutations are often discussed as part of evolutionary mechanisms. In this sense, mutations may be considered a part of a creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips • A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame is reformed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. • The authors have noted elsewhere that “A random mutation is like a random shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Active Lecture Tips  See the Media Review: “Learn.Genetics” Genetic Science Learning from the University of Utah on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Demonstrating a Frame Shift Mutation on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 23

10.16 Mutations within a gene can be divided into two general categories. Nucleotide substitutions involve the replacement of one nucleotide with another pair of nucleotides. have no effect at all (silent mutation) change the amino acid coding (missense mutation) which produces a different amino acid lead an improved protein that enhances the success of the mutant organism and its descendants, change an amino acid into a stop codon, (nonsense mutation) Student Misconceptions and Concerns • Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. • Mutations are often discussed as part of evolutionary mechanisms. In this sense, mutations may be considered a part of a creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips • A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame is reformed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. • The authors have noted elsewhere that “A random mutation is like a random shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Active Lecture Tips  See the Media Review: “Learn.Genetics” Genetic Science Learning from the University of Utah on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Demonstrating a Frame Shift Mutation on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 24

10.16 Mutations can affect genes Nucleotide insertions or deletions of one or more nucleotides in a gene may cause a frameshift mutation, which alters the reading frame (triplet grouping) of the genetic message, lead to significant changes in amino acid sequence, and produce a nonfunctional polypeptide. Student Misconceptions and Concerns • Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. • Mutations are often discussed as part of evolutionary mechanisms. In this sense, mutations may be considered a part of a creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips • A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame is reformed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. • The authors have noted elsewhere that “A random mutation is like a random shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Active Lecture Tips  See the Media Review: “Learn.Genetics” Genetic Science Learning from the University of Utah on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Demonstrating a Frame Shift Mutation on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 25

10.16 Mutations can affect genes Mutagenesis is the production of mutations. Mutations can be caused by spontaneous errors that occur during DNA replication or recombination or by mutagens, which include high-energy radiation such as X-rays and ultraviolet light and chemicals. Student Misconceptions and Concerns • Beginning college students are often intensely focused on writing detailed notes. The risk is that they will miss the overall patterns and the broader significance of the topics discussed. Consider a gradual approach to the subjects of transcription and translation, beginning quite generally and testing comprehension, before venturing into the finer mechanics of each process. • Mutations are often discussed as part of evolutionary mechanisms. In this sense, mutations may be considered a part of a creative process. The dual nature of mutations, potentially deadly yet potentially innovative, should be clarified. Teaching Tips • A simple way to demonstrate the effect of a reading frame shift is to have students compare the following three sentences. The first is a simple sentence. However, look what happens when a letter is added (2) or deleted (3). The reading frame is reformed into nonsense. (1) The big red pig ate the red rag. (2) The big res dpi gat eth ere dra g. (3) The big rep iga tet her edr ag. • The authors have noted elsewhere that “A random mutation is like a random shot in the dark. It is not likely to improve a genome any more than shooting a bullet through the hood of a car is likely to improve engine performance!” Active Lecture Tips  See the Media Review: “Learn.Genetics” Genetic Science Learning from the University of Utah on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity.  See the Activity Demonstrating a Frame Shift Mutation on the Instructor Exchange. Visit the Instructor Exchange in the MasteringBiology instructor resource area for a description of this activity. 26

Significance of Mutations Many mutations have little or no effect on gene expression. Some mutations are the cause of genetic disorders. Beneficial mutations may produce proteins with new or altered activities that can be useful. The larval skate at the bottom has had it’s gene mutated in a lab. This gene in the skate is the same gene in humans that codes for hand shape.