Ch. 10 Notes DNA: Transcription and Translation

GOALS Compare the structure of RNA with that of DNA Summarize the process of transcription Relate the role of codons to the sequence of amino acids that results after translation Outline the major steps of translation Discuss the evolutionary significance of the genetic code Describe how the lac operon is turned on or off Summarize the role of transcription factors in regulating eukaryotic gene expression Describe how eukaryotic genes are organized Evaluate three ways that point mutations can alter genetic material

Decoding the Information in DNA RNA 1. Nucleic acid made of nucleotides linked together 2. Single stranded

Decoding the Information in DNA RNA 3. Contains 5C ribose sugar (one more oxygen than DNA)

Decoding the Information in DNA RNA 4. Has A, G and C bases, but no T 5. Thymine replaced by uracils (which pairs with adenine)

Decoding the Information in DNA Transcription Instructions for making protein are transferred from a gene to an RNA molecule

Decoding the Information in DNA Translation Two types of RNA are used to read instructions on RNA molecule and put amino acids together to make the protein

Decoding the Information in DNA Gene Expression Protein synthesis Protein making process based on information encoded in DNA

TRANSCRIPTION Transfers info from a gene on DNA to RNA In prokaryotes- occurs in cytoplasm In eukaryotes- occurs in nucleus

TRANSCRIPTION Transcription (STEPS) 1. RNA polymerase binds to start signal “promoter” on DNA 2. RNA polymerase unwinds and opens DNA double helix

TRANSCRIPTION Transcription (STEPS) 3. RNA polymerase reads genes- adds and links matching nucleotides by base pairing (A-U and G-C)

TRANSCRIPTION Transcription (STEPS) 4. RNA polymerase reaches stop signal at end of gene 5. As RNA polymerase works, a single strand of RNA grows

TRANSCRIPTION Transcription (STEPS) 6. DNA helix zips itself back up as RNA polymerase passes by

TRANSCRIPTION 7. Many identical RNA molecules are made simultaneously (STEPS) 7. Many identical RNA molecules are made simultaneously Feather like appearance in photos

The GENETIC CODE Messenger RNA mRNA Made when cells need a protein made Delivers protein making instructions from gene to translation site Instructions written in codons

The GENETIC CODE Codons Three nucleotide sequences along mRNA 64 possible codons Each corresponds to: An amino acid OR A stop signal OR A start signal

Can You Tell Me? 1. During DNA replication, what molecule “reads” the strand of DNA to make the matching strand? 2. During transcription, what molecule “reads” the DNA? 3. What material does the transcription process create?

The GENETIC CODE RNA’s role in translation Takes place in cytoplasm Transfer RNA (tRNA) and ribosomes help in protein synthesis

The GENETIC CODE Transfer RNA tRNA Single strand, carries amino acid Folded shape Contains anticodon

The GENETIC CODE Anticodon 3 nucleotides on tRNA that are complementary to a mRNA codon

The GENETIC CODE Ribosomal RNA rRNA makes up part of ribosomes

The GENETIC CODE Translation process 1. mRNA leaves nucleus, enters cytoplasm 2. Ribosome hooks onto mRNA at start codon

The GENETIC CODE Translation process 3. tRNA attaches to ribosome subunit and binds to mRNA Anticodon of tRNA binds to codon of mRNA

The GENETIC CODE Translation process 4. tRNA drops off amino acid its carrying 5. Another tRNA comes and drops an amino acid off

The GENETIC CODE Translation process 6. Another tRNA enters, first tRNA leaves

The GENETIC CODE Translation process 7. Each amino acid bonded to previous one to form a chain 8. tRNA detaches leaving amino acid attached to remaining tRNA

The GENETIC CODE Translation process 9. Repeats until ribosomal subunit reaches stop codon 10. Newly made protein is released

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Assessment One Distinguish two differences between RNA structure and DNA structure Explain how RNA is made during transcription Interpret the genetic code to determine the amino acid coded for by the codon CCU Compare the roles of the three different types of RNA during translation What is the maximum number of amino acids that could be coded for by a section of mRNA with the sequence GUUCAGAACUGU?

Protein Synthesis Protein Synthesis in Prokaryotes Requires too much energy and too many materials for cell to make every protein encoded for by the DNA at all times Gene expression can be regulated according to cell needs Ex: E. coli bacteria

Regulating Protein Synthesis Lac Operon 1. Lactose in dairy products enters your intestines 2. E. coli there can use lactose for nutrition (to make glucose and galactose)

Regulating Protein Synthesis Lac Operon 3. Three genes for breaking down lactose located next to each other on DNA (can turn them on or off) Genes on: they’re ready to be transcribed and translated

Regulating Protein Synthesis Lac Operon 4. These 3 genes turn on in presence of lactose and turn off in its absence

Regulating Protein Synthesis Lac Operon 5. Operator- area on DNA (touching start/promoter) that acts as on and off switch Can block RNA polymerase from transcribing

Regulating Protein Synthesis Lac Operon 6. Operon consists of Operator Promoter Three genes All work together to control lactose metabolism

Regulating Protein Synthesis Lac Operon 7. No lactose present Lac operon is turned off when repressor protein binds to DNA Repressor blocks RNA polymerase from binding

Regulating Protein Synthesis Lac Operon 8. In presence of lactose Lactose binds to repressor changing its shape Causes repressor to fall off DNA Allows RNA polymerase to bind and transcribe

Regulating Protein Synthesis Protein synthesis in eukaryotes Most gene regulation is to control the onset of transcription (binding of RNA polymerase)

Regulating Protein Synthesis Protein synthesis in eukaryotes Transcription Factors- regulatory proteins that help rearrange RNA polymerase into the correct position

Intervening DNA Intervening DNA in Eukaryotic Genes 1. Introns- longs segments of nucleotides with no coding information Break up DNA/genes

Intervening DNA Intervening DNA in Eukaryotic Genes 2. Exons- actual genes that are translated into proteins

Intervening DNA Intervening DNA in Eukaryotic Genes 3. After transcription, introns in mRNA are cut out by spliceosomes Exons are stitched back together

Intervening DNA Intervening DNA in Eukaryotic Genes 4. Large numbers of exons and introns allows evolutionary flexibility because they can be shuffled about to make new genetic codes

Mutations Mutations Changes in DNA of a gene are rare When in body cells, only affect individual When in gametes, offspring can be affected

Mutations Mutations A. Gene rearrangements- entire gene moved to a new location (disrupts its function)

Mutations Mutations B. Gene alterations- changes a gene Usually results in wrong amino acid being hooked into protein (disrupts protein function)

Mutations Mutations C. Point Mutation- single nucleotide changes

Mutations Mutations D. Insertion Mutation- extra piece of DNA is inserted

Mutations Mutations E. Deletion Mutation- segments of gene are lost

Mutations Mutations F. Frame shift Mutations- causes gene to be read in wrong 3 nucleotide sequence Ex THE CAT ATE Remove C THE ATE TE (makes no sense)

WEBSITES DNA Workshop Transcription Interactive Transcribing and Translating a Gene Protein Synthesis Animation Transcription Animation Translation Movie Protein Translation Animation Animation of Translation Protein Synthesis Movie Transcription Game Protein Synthesis Tutorial