Gene Expression: Gene Expression Overview Gene expression is the - PDF document

Slide 1 / 124 Slide 2 / 124 New Jersey Center for Teaching and Learning Progressive Science Initiative This material is made freely available at www.njctl.org and is intended for the non-commercial use of students and teachers. These materials may not be used for any commercial purpose without the written permission of the owners. NJCTL maintains its website for the convenience of teachers who wish to make their work available to other teachers, participate in a virtual professional learning community, and/or provide access to course materials to parents, students and others. Click to go to website: www.njctl.org Slide 3 / 124 Slide 4 / 124 Big Idea 3: Part C Click on the topic to go to that section Big Idea 3: Living systems store, retrieve, · Gene Expression: Overview transmit and respond to · Gene Expression: Transcription information essential to life · Gene Expression: Translation processes. · Genetics of Development · Mutations · Genetics of Viruses Slide 5 / 124 Slide 6 / 124 Gene Expression: Gene Expression Overview Gene expression is the molecular process of reading the order of nucleic acids in a DNA molecule and making the product it codes for. This product is usually a protein but RNA is also coded for in genes. Gene expression occurs whenever a specific protein or RNA molecule is needed by the cell. Return to Table of Contents

Slide 7 / 124 Slide 8 / 124 DNA to RNA to Protein RNA RNA is essential for bringing the genetic information stored in the DNA to where it can Expressing the information stored on a gene into a be used in the cell. protein requires : Recall that RNA is made up of a sugar molecule · translating from the 4 letter language of DNA to RNA and phosphate group "backbone" and a sequence of nitrogen bases: · Then from the 4 letter language of RNA, to the 20 letter language of proteins (their amino acid Adenine (A) sequence). Uracil (U) Guanine (G) Citosine (C) These bases hydrogen bond in pairs: A bonds to U and G bonds to C. Slide 9 / 124 Slide 10 / 124 RNA Proteins A strand with bases in the sequence: Proteins are large biological molecules consisting of one or more chains of amino acids. Proteins perform a vast array of functions ACUAGGUACAUG within living organisms, including catalyzing metabolic reactions, replicating DNA, has a different shape, and functions responding to stimuli, and transporting differently, than a strand with the sequence: molecules from one location to another. CUAGAACAGUCAA Letter changes result in a new shape, and new functions. Slide 11 / 124 Slide 12 / 124 Proteins Codons Proteins differ from one another primarily The mRNA "message" is read in 3-letter in their sequence of amino acids, which is words called codons. Each codon codes dictated by the nucleotide sequence of for an amino acid or tells the process to their genes, and which usually results in stop. folding of the protein into a specific three- dimensional structure that determines its activity. There are 64 codons (4x4x4) but only 20 amino acids. So some codons code for the same amino acid.

Slide 13 / 124 Slide 14 / 124 The Universal Genetic Code The Universal Genetic Code · 61 of the codons code This is called a "universal" code because ALL LIFE uses for an amino acid the same genetic code ... from the smallest bacteria or virus to the largest animal or tree. · 3 of the remaining codons are "STOP" This tells us that this code goes back billions of years , in codons that do not code the first cell...or even before that. for an amino acid. They just signal that translation is over. If there were alternative codes that could work, they would have appeared in nature. · 1 codon that codes for the amino acid There are very minor alterations, but they are rare and "methionine" is also the insignificant in their effect. "START" codon. Methionine is always the first amino acid in a protein. Slide 15 / 124 Slide 16 / 124 1 What is a codon? The codon UAA specifies: 2 A a 3 base sequence on tRNA A Adenine B a 3 base sequence on mRNA B Glycine (Gly) C a 3 base sequence on DNA D B and C C STOP D Arginine E Valine answer Slide 17 / 124 Slide 18 / 124 The codon GGG 3 The codon GAC specifies: 4 specifies: Adenine Adenine A A Glycine Glycine B B STOP STOP C C Arginine Arginine D D Valine E E Aspartic Acid answer answer

Slide 19 / 124 Slide 20 / 124 Why is Methionine the very first amino acid in all 5 Steps of Gene Expression proteins? A because it is coded by the stop codon B because it is coded for by AUG which is the start codon DNA Gene expression occurs in two steps: C Methionine is coded for by more than one codon 1. The gene is copied from DNA into D none of the above RNA through a process called transcription. RNA 2. The RNA build a protein in a process answer called translation. Protein Slide 21 / 124 Slide 22 / 124 The Central Dogma The Central Dogma The Central Dogma is a one way process. Changes in DNA affect mRNA and protein. transcription translation DNA RNA PROTEIN transcription translation DNA mRNA Protein replicatio n But changes in proteins or mRNA do not affect the DNA. The processes of replication, transcription and translation are so critical that they are called the Central Dogma of Biology. This will have important implications when we study genetics. A "Dogma" is a postulate; an idea; a philosophy. It is "Central" because it is what life is based on. Slide 23 / 124 Slide 24 / 124 6 What is meant by "gene expression"? 7 Which one of the following sequences best describes the Central Dogma of biology? A making the protein or RNA coded in the nucleic acid B making amino acids so they can be made into protein A RNA to DNA to RNA to Protein C making tRNA only B DNA to RNA to Protein D folding of the protein C Protein to RNA to DNA D DNA to Amino Acid to RNA to Protein answer answer

Slide 25 / 124 Slide 26 / 124 Gene Anatomy Gene Expression: Transcription Return to Table of Contents Slide 27 / 124 Slide 28 / 124 Gene Anatomy Gene Anatomy This control region is where transcription factors bind to the gene. When all the necessary factors are combined RNA polymerase can bind to the gene and initiate transcription . Slide 29 / 124 Slide 30 / 124 The First Step - Transcription Transcription - Pre-Initiation The first step of transcription is called pre-initiation. RNA Transcription is the first step of gene expression, in which a polymerase and cofactors bind to DNA and unwind it, creating an particular segment of DNA is copied into RNA by the enzyme RNA initiation bubble . This is a space that grants RNA polymerase polymerase. access to a single strand of the DNA molecule. olymerase Non- Template Promotor Region

Slide 31 / 124 Slide 32 / 124 Transcription - Initiation Template vs. Non-Template Strands To begin, an enzyme called RNA Polymerase attaches to the Promoter region on the DNA. The RNA polymerase never attaches to the strand that actually contains the gene. The Promoter is a specific sequence of bases that the RNA polymerase recognizes. The strand with the genes is called the "non-template strand." This IS NOT the strand that is transcribed. olymerase The other strand is the mirror image of the first, it carries the mirror image of the gene, not the gene itself. It is called the Non- "template strand." Template This IS the strand where the RNA polymerase attaches. Promotor Region Slide 33 / 124 Slide 34 / 124 Transcription: DNA Strands 8 The strand that is transcribed into RNA is called the This makes sense in that the RNA will be the mirror image A Template Strand of the DNA it is transcribed from. And the non-coding strand is the mirror image of the gene. B Non Template Strand C RNA Strand non-template strand of DNA D Amino Acid Strand template strand of DNA transcription of template strand answer RNA Note: the non-template strand of DNA (the gene) matches the new RNA strand Slide 35 / 124 Slide 36 / 124 9 The transfer of genetic material from DNA to RNA is called: 10 Genes are located on the A Template Strand A translation B Non Template Strand C RNA Strand B transcription D Amino Acid Strand C elongation D promotion answer answer