Agenda 3/8 Transcription Notes Epigenetics Activity Turn in: Nothing Homework: Transcription video and notes, Chp 14 reading/notes, RNA reading/questions * Please place your cell phone in your folder for the duration of class* 1

Protein Synthesis - The “Stuff of Life”

3 Proteins Proteins are the “workhorse” molecule found in organisms. The blue print for proteins is coded in the DNA of the organism.

Create a list of 10 specific proteins we have studied this year 4

Uses of Proteins 5

Conclusion One gene produces one enzyme. Later it was modified One gene produces one protein. 6

What is a gene? Today the definition for a gene is a sequence of DNA molecules that can direct the synthesis of a molecule product. Genes do not all code for a protein, but all do code for an RNA molecule. Some of those RNAs are translated into protein, but many serve other functions, such as gene regulation. 7

Overview of Protein Synthesis DNA is located in the nucleus Proteins are made in the cytoplasm RNA is the intermediate between the DNA code and the actual synthesis of a protein 8

Structure of RNA versus DNA 9

RNA vs. DNA RNADNA Single strandedDouble stranded RiboseDeoxyribose U instead TT instead of U Nucleus and cytoplasmRestricted to nucleus & organelles Multiple usesUsed as template for RNA synthesis and proteins 10

Three Main Types of RNA 11

12 There are different types of RNA mRNA-carries the information from the DNA gene to the cytoplasm. Determines the sequence of amino acids for a protein tRNA-brings the correct amino acid to the ribosome and mRNA in translation rRNA-found on ribosomes and used to "connect" the tRNA to the mRNA snRNA-found on spliceosomes. Used to remove introns. SRP RNA-part of the signal recognition particle used to bring a translating ribosome to the E.R. and threads the emerging polypeptide chain into the lumen of the E.R.

Differences in Protein Synthesis between Prokaryotes and Eukaryotes Prokaryotes do not have introns like eukaryotes. RNA in prokaryotes does not have to be processed like eukaryotes. Transcription and translation can be simultaneous in prokaryotes. 13

Genetic Code Amino acids are coded for by a triplet of DNA nucleotides called a codon. 14

Come up with 3 different observations about the codon chart 15

Genetic Code 16 The code has redundancy (What does this mean? Each codon only codes for one amino acid. The code is a universal code meaning almost all cells use the same code. A eukaryotic gene can be expressed in a prokaryotic cell.

Specifying or Coding for a Polypeptide This gene designates that the following peptide chain be made with the amino acids in this particular order. 17

Transcription Overview Transcription-RNA synthesis from a DNA template Initiation Elongation Termination RNA processing 18

Initiation There is a region prior to beginning of a gene where the RNA polymerase attaches called the promoter region. The promoter region determines which side of the gene will be transcribed. In a prokaryotic cell, the RNA polymerase attaches directly to the region In a eukaryotic cell there are transcription factors (proteins) which help facilitate the attachment of the RNA polymerase. 19

Initiation 20

Elongation Elongation- RNA polymerase unwinds the DNA and base pairs RNA nucleotides to the DNA gene. RNA is made 5′ → 3 ′ so the DNA gene is 3′ → 5′. 21

22 Termination RNA synthesis proceeds until the RNA polymerase encounters a sequence that triggers its dissociation.

RNA Processing Eukaryotic RNA processing 5' cap is added. At the 3' end adenine nucleotides are added (poly-A-tail). Introns are removed 23

Removing Introns A spliceosome removes the introns. Spliceosomes are composed of smaller particles called snRNP (made of proteins and snRNA). The spliceosome will splice the intron at a specific RNA sequence. 24

RNA Processing Different exons are recombined in different ways for certain mRNAs. This increases the number of different proteins. 25

Exon Shuffling and Different Proteins Proteins often have a modular architecture consisting of discrete regions called domains In many cases, different exons code for the different domains in a protein Exon shuffling may result in the evolution of new proteins. 26

Ready for Translation This mRNA has been processed and is called mature mRNA. It is ready to go to the cytoplasm for translation. 27

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