1. DNA, RNA structure 2. Transcription, translation

DNA is a double-stranded helix James Watson and Francis Crick worked out the three-dimensional structure of DNA, based on work by Rosalind Franklin Figure 10.3A, B

DNA and RNA are polymers of nucleotides DNA is a nucleic acid, made of long chains of nucleotides Phosphate group Nitrogenous base Nitrogenous base (A, G, C, or T) Sugar Phosphate group Nucleotide Thymine (T) Sugar (deoxyribose) DNA nucleotide Polynucleotide Sugar-phosphate backbone Figure 10.2A

DNA has four kinds of bases, Adenine(A), Thymine (T), Cytosine (C), and Guanine (G) Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Figure 10.2B

Each strand of the double helix is oriented in the opposite direction Anit-Parellel: means parellel but moving in different directions 5 end 3 end P P P P P P P P 3 end 5 end Figure 10.5B

Nitrogenous base (A, G, C, or U) RNA is also a nucleic acid different sugar (ribose) Uracil instead of Thymine Still has Adenine, Guanine, Cytosine Single strand, usually Nitrogenous base (A, G, C, or U) Phosphate group Uracil (U) Sugar (ribose) Figure 10.2C, D

Types of RNA Genetic information copied from DNA is transferred to 3 types of RNA: __________ RNA: mRNA Copy of information in DNA that is brought to the ribosome and translated into protein by tRNA & rRNA. __________ RNA: rRNA Most of the RNA in cells is associated with structures known as ribosomes, the protein factories of the cells. It is the site of translation where genetic information brought by mRNA is translated into actual proteins. ___________ RNA: tRNA Brings the amino acid to the ribosome that mRNA coded for. Messenger Ribosomal Transfer From the Virtual Cell Biology Classroom on ScienceProfOnline.com Images: Blueprint, clipart; Factory, Andreas Praefcke; Truck, PRA.

The information constituting an organism’s genotype is carried in its sequence of bases The DNA is transcribed into RNA, which is translated into a chain of amino acids Bases of Central Dogma DNA TRANSCRIPTION RNA TRANSLATION Protein Figure 10.6A

Transcription produces mRNA RNA nucleotide RNA polymerase Direction of transcription Template strand of DNA Newly made RNA Figure 10.9A

In transcription, DNA helix unzips RNA polymerase In transcription, DNA helix unzips DNA of gene Promoter DNA Terminator DNA Initiation RNA nucleotides line up along one strand of DNA, following the base-pairing rules single-stranded messenger RNA peels away and DNA strands rejoin Elongation Area shown in Figure 10.9A Termination Growing RNA Completed RNA RNA polymerase Figure 10.9B

RNA transcripts of DNA

Translation of mRNA into amino acids The “words” of the DNA “language” are triplets of bases called codons The codons in a gene specify the amino acid sequence of a protein In other words, codons are every 3 bases.

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

An exercise in translating the genetic code Transcribed strand DNA Transcription RNA Start codon Stop codon Translation Polypeptide Figure 10.8B

Transfer RNA molecules serve as interpreters during translation In the cytoplasm, a ribosome attaches to the mRNA and translates its message into a protein The process is aided by transfer RNAs Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Figure 10.11A

Each tRNA molecule has a triplet anti-codon on one end and an amino acid attachment site on the other Amino acid attachment site Anticodon Figure 10.11B, C

Ribosomes build chains of amino acids Next amino acid to be added to protein Growing protein tRNA molecules P site A site Growing protein Large subunit tRNA P A mRNA mRNA binding site Codons mRNA Small subunit Figure 10.12A-C

An initiation codon marks the start of an mRNA message AUG = methionine Start of genetic message End Figure 10.13A

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

How does translation happen? The mRNA moves one codon at a time relative to the ribosome A tRNA pairs with each codon, adding an amino acid to the growing protein A STOP codon causes the mRNA-ribosome complex to fall apart This results in a chain of amino acids Amino Acid (AA) + AA + AA + AA…etc = Protein

Transcription RNA RNA polymerase DNA During transcription, RNA polymerase uses one strand of DNA as a template to assemble nucleotides into a strand of RNA.

Translation Lysin e tRNA mRN A Ribosome During translation, or protein synthesis, the cell uses information from messenger RNA to produce proteins. The cell uses all three main forms of RNA during this process. mRN A Translation direction Ribosome Copyright Pearson Prentice Hall

Complete -Protein Synthesis Worksheet -Book Worksheet Pause for Worksheet Complete -Protein Synthesis Worksheet -Book Worksheet

What molecules are present in this photo? Red object = ? Figure: 14-12 Title: Mass production. Caption: a. An mRNA transcript can be translated by many ribosomes at once, resulting in the production of many copies of the same protein. b. A micrograph of this process in operation. The figure shows two mRNA strands with ribosomes spaced along their length. In the upper strand, translation is underway and polypeptides can be seen emerging from the ribosomes. What molecules are present in this photo? Red object = ?

Table 14.2 Types of RNA Type of RNA Functions in Function Messenger RNA (mRNA) Nucleus, migrates to ribosomes in cytoplasm Carries DNA sequence information to ribosomes Transfer RNA (tRNA) Cytoplasm Provides linkage between mRNA and amino acids; transfers amino acids to ribosomes Figure: Table 14.2 Title: Types of RNA. Caption: Ribosomal RNA (rRNA) Cytoplasm Structural component of ribosomes

Review: The flow of genetic information in the cell is DNARNAprotein The sequence of codons in DNA spells out the primary structure of a protein A chain of amino acids form proteins that cells and organisms use

Overview Eukaryotic Cell ______________ Synthesis of RNA under the direction of DNA (mRNA). Actual synthesis of a polypeptide (protein) under the direction of mRNA. Transcription Translation From the Virtual Cell Biology Classroom on ScienceProfOnline.com Diagram: Transcription & Translation, NIH

Complete -DNA Molecule & Replication Pause for Worksheet Complete -DNA Molecule & Replication

So how is DNA read to make Amino acids We use the Genetic Coding Chart Virtually all organisms share the same genetic code- the sequence is what is important

This is another one Second Base U C A G UUU UCU UAU UGU U phe tyr cys 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

Before we begin In DNA A binds with T (like AT&T) C binds with G (like Cover Girl) RNA is the same BUT there is no T It is a U so A and U bind together

Create a DNA sequence with 30 bases Step 1: Create a DNA sequence with 30 bases Must start with TAC Must end with ATT After that you are good to go with any bases

Step 2: Using your DNA, make a complimentary mRNA strand

Step 3: Using your mRNA strand Start at the beginning and circle every 3 codons

Look at your first codon Step 4: Look at your first codon Match the first letter, second letter and third letter to the Genetic Coding Chart. Write the Amino Acid under the circled codon

Continue until all codons are labeled with an amino acid Step 5: Continue until all codons are labeled with an amino acid Now you have a chain of Amino Acids Also called a PROTEIN

Example methionine proline leucine DNA strand A – T – G – C – C – T – T – T – G T – A – C – G – G – A – A – A – C mRNA strand A – U – G – C – C – U – U – U – G 1st codon A-U-G amino acid = methionine 2nd codon C-C-U amino acid = proline 3rd codon U-U-G amino acid = leucine methionine proline leucine

Complete the 3 Genetic Coding Worksheets Pause for Worksheet Complete the 3 Genetic Coding Worksheets

(You must be in PPT slideshow view to click on links.) Confused? Here are links to fun resources that further explain genetic transcription & translation: Molecular Genetics: Transcription & Translation Main Page on the Virtual Cell Biology Classroom of Science Prof Online. “That Spells DNA” song by Jonathan Coulton. DNA Transcription step-through animation by John Kyrk. Transcribe & Translate a Gene, from University of Utah. DNA Transcription and Protein Assembly animated movie by RedAndBrownPaperBag. Genetic by Sonic Youth. Transcription and Translation animated movie from PBS production “DNA: The Secret of Life. “The Protein Synthesis Song” by MrsPurpleMonster18. (You must be in PPT slideshow view to click on links.) Smart Links From the Virtual Cell Biology Classroom on ScienceProfOnline.com