Transcription and Translation Image source: http://en.wikipedia.org/wiki/DNA_repair © copyright- All rights reserved www.cpalms.org

Standard(s): SC.912.L.16.5 Explain the basic processes of transcription and translation, and how they result in the expression of genes.   Learning objectives: Students will compare and contrast the processes of transcription and translation. Students will model how transcription and translation lead to the expression of genes. The teacher will introduce the standard and learning objectives.

DNA RNA transcription translation Amino acid Protein Codon/ anticodon This a list of key words needed to develop understanding of transcription and translation. Image source: http://englishedrissis.blogspot.com/2011/04/power-of-words.html

How are proteins made according to the code in DNA? Guiding question: How are proteins made according to the code in DNA? Guiding question: How are proteins made according to the code in DNA? It is used to anchor the lesson for teachers to guide students understanding of the transcription and translation processes. The figure shows a DNA molecule on the left and a protein molecule on the right as a visual for students to make a connection. Image source: http://www.hartnell.edu/tutorials/biology/dnareplication.html and http://es.wikipedia.org/wiki/Prote%C3%ADna_globular  

cell chromosome nucleus DNA gene This slide serves as a review of the location, and structure of DNA and genes. Emphasize how chromosomes are a condensed version of DNA. Note: The teacher can delete or modify the location of the slide. Image source: http://pixabay.com/en/genetics-chromosomes-rna-dna-156404/ DNA gene

Transcription Transcription: is the process in which DNA is unzipped in a particular gene to create a copy (mRNA) that will code for a specific protein needed by the cell/ living organism. The nucleotide bases from DNA are copied to mRNA according to the base paring rules (C pairs with G, A pairs with T in DNA and U in mRNA). The copy gets made by the RNA polymerase adding the corresponding bases. Once completed, the newly formed mRNA is sent to the ribosome complex in the cytoplasm through the nucleopores. Emphasize to students the advantages of mRNA (codes a single protein and it’s smaller and can easily leave the nucleus) Image source: http://microbe.net/simple-guides/fact-sheet-dna-rna-protein/

Transcription Transcription- is the process in which DNA is unzipped in a particular gene to create a copy (mRNA) that will code for a specific protein needed by the cell/ living organism. DNA makes RNA

Transcription RNA polymerase “unzips” DNA RNA polymerase copies the nucleotide bases from DNA to mRNA according to the base paring rules in the 5’ to 3’ direction (adds to the 3’ end) C pairs with G, A pairs with T in DNA (and U in mRNA) Telomere sequences are lost with each replication. Cancer, aging

Transcription Once completed, the newly formed mRNA is sent to the ribosome complex (in the cytoplasm) to make a protein *Went from DNA to mRNA!! Ribosome complex is in the cytoplasm through the nucleopores.

Transcription in a nutshell Occurs inside the nucleus Specific gene is copied into mRNA (messenger) One mRNA codes a single protein End result is the code for a single protein Transcription in a nutshell: the teacher will go over the key events of transcription. Occurs inside the nucleus Specific gene is copied into mRNA One mRNA codes a single protein End result is the code for a single protein Image source: http://pixabay.com/en/sticky-note-paper-pin-notes-294627/ RNA base paring rules A pairs with U C pairs with G

Translation Translation- is the process of changing the mRNA code coming from the DNA into amino acids that will form the protein needed by the cell/ living organism. RNA makes Protein

Translation mRNA bind with a ribosome forming a complex in which different tRNA brings an amino acid by matching the mRNA according to the base paring rules for RNA. mRNA and tRNA (transport) function in triplets called codon and anticodon respectively Work like a key and lock system. Ribosome complex can be easily compared to a factory with a production line!

Codon Codon: The teacher can use this image to show different view of the codon and clarify students misunderstanding. Image source: http://en.wikipedia.org/wiki/Genetic_code

Each tRNA molecule has a triplet anticodon on one end and an amino acid attachment site on the other Figure 10.11B, C

mRNA, a specific tRNA, and the ribosome subunits assemble during initiation Large ribosomal subunit Initiator tRNA P site A site Start codon Small ribosomal subunit mRNA 1 2 Figure 10.13B

Amino acid Polypeptide A site P site Anticodon mRNA 1 Codon recognition mRNA movement Stop codon New peptide bond 2 Peptide bond formation Scientists have identified around 20 amino acids that are essential to proteins and based of paring rules have created a table called the mRNA codon chart that shows what amino acids corresponds to the mRNA codon been coded. 3 Translocation Figure 10.14

Translation In protein production there are codons that will indicate to the ribosome when to start and when to end. Once the chain of up to several hundreds of amino acids is completed, the process stops and the protein gets sent to the endoplasmic reticulum to be packed and released. The order of amino acids determines the shape and function of the newly formed protein.

Gene 1 Gene 3 DNA molecule Gene 2 DNA strand TRANSCRIPTION RNA Codon TRANSLATION Polypeptide Amino acid Figure 10.7

Virtually all organisms share the same genetic code “unity of life” Second Base U C A G UUU UCU UAU UGU U phe tyr cys UUC UCC UAC UGC C U ser UUA UCA UAA stop UGA stop A leu UUG UCG UAG stop UGG trp G CUU CCU CAU CGU U his CUC CCC CAC CGC C C leu pro arg CUA CCA CAA CGA A gln CUG CCG CAG CGG G First Base Third Base AUU ACU AAU AGU U asn ser AUC ile ACC AAC AGC C A thr AUA ACA AAA AGA A lys arg Figure: 14-07 Title: The genetic code dictionary. Caption: If we know what a given mRNA codon is, how can we find out what amino acid it codes for? This dictionary of the genetic code offers a way. In Figure 14.5, you saw that the codon CGU coded for the amino acid arginine (arg). Looking that up here, C is the first base (go to the C row along the “first base” line), G is the second base (go to the G column under the “second base” line) and U is the third (go to the codon parallel with the U in the “third base” line). AUG met (start) ACG AAG AGG G GUU GCU GAU GGU U asp GUC GCC GAC GGC C G val ala gly GUA GCA GAA GGA A glu GUG GCG GAG GGG G

mRNA codon chart Alanine : Ala Arganine: Arg Asparagine: Asn   Alanine : Ala Arganine: Arg Asparagine: Asn Aspartic acid: Asp Cysteine: Cys Glutamic acid: Glu Glutamine: Gln Glycine: Gly Histidine: Hist Isoleucine: Ile Leucine: Leu Lysine:Lys Methionine: Met Phenylalanine:Phe Proline:Pro Serine: Ser Threonine: Thr Tryptophan: Trp Tyrosine:Tyr Valine:Val START: Met Codon chart: Scientists have identified around 20 amino acids that are essential to proteins and based of paring rules have created a table called the mRNA codon chart that shows which amino acids corresponds to the mRNA codon been used. Guide students on how to use the codon chart by looking at the first, second and third base. Image source: http://biology-forums.com/index.php?topic=71640.0

Translation in a nutshell Occurs in the cytoplasm Requires a ribosome Ribosomal complex= ribosome + mRNA+ tRNA mRNA contains code for specific tRNA Different tRNA’s bring different amino acids to the ribosome End result is a protein! Translation in a nutshell: the teacher will go over the key events of translation. Occurs in the cytoplasm Requires a ribosome Ribosomal complex: ribosome + mRNA+ tRNA mRNA contains code for specific tRNA Different tRNA’s bring different amino acids to the ribosome End result is a protein RNA base paring rules A pairs with U C pairs with G

The teacher can use this slide to give students another view of transcription and translation and review the process all together. Image source: http://ebbailey.files.wordpress.com/2011/03/biotrans.gif

NUCLEUS CYTOPLASM (ribosome) The teacher can use this slide to give students a summarized view of transcription and translation. Image source: http://commons.wikimedia.org/wiki/File:0328_Transcription-translation_Summary.jpg

DNA makes RNA makes Protein Central Dogma DNA makes RNA makes Protein DNA  RNA = transcription RNA  Protein= translation

How do you go from DNA to the color of your eyes? The teacher will refer back to the engage question: How do you go from DNA to the color of your eyes? And guide students on the development of eye color.

That controls levels of melanin 3 genes code for eye color Transcription and translation Enzyme (protein) That controls levels of melanin There are 3 genes that code for the color of the eyes. By transcription and translation a protein is made. That protein is the enzyme tyrosinase which catalyzes the amino acid tyrosine and controls the amount of melanin in the cells (melanocytes) of the iris. The higher content of melanin the darker the eye color is. Emphasize that DNA has the code to make the enzyme that will control the level of melanin and ultimately the color of the eyes, because the enzyme is a protein. Image source: http://ibmmyositis.com/chromosome.gif, http://upload.wikimedia.org/wikipedia/commons/2/22/DHRS7B_homology_model.png, http://smithlhhsb122.wikispaces.com/file/view/melanin.gif/397497882/melanin.gif

Mutations can change the meaning of genes Mutations are changes in the DNA base sequence caused by errors in DNA replication or by mutagens change of a single DNA nucleotide causes sickle-cell disease

Sickle-cell hemoglobin Normal hemoglobin DNA Mutant hemoglobin DNA mRNA mRNA Normal hemoglobin Sickle-cell hemoglobin Glu Val Figure 10.16A

Types of mutations NORMAL GENE mRNA Protein Met Lys Phe Gly Ala BASE SUBSTITUTION Met Lys Phe Ser Ala BASE DELETION Missing Met Lys Leu Ala His Figure 10.16B

Types of Mutations Missense (Substitution) Nonsense (substitution) Deletion (frameshift) Insertion (frameshift)

Chromosomal changes can be large or small Deletion Homologous chromosomes Duplication Inversion Reciprocal translocation Nonhomologous chromosomes Figure 8.23A, B