Biology 105 Chapter 13: Gene Expression Pages

Student Outcomes Compare the structures of DNA and RNA Explain why the genetic code is redundant and universal. Explain the process of protein synthesis

Student Outcomes Explain how mutations occur Describe several genetic disorders

Gene Expression Series of steps where DNA specifies the makeup of the cell’s proteins. One-gene, one-enzyme: DNA (genes) code for one enzyme or one protein. Proposed in 1940’s by Beadle and Tatum

RNA – ribonucleic acid The link between DNA and protein synthesis Usually single stranded Has Uracil instead of Thymine (still pairs with adenine) DNA is copied to RNA - Transcription

Types of RNA Messenger RNA (mRNA) – carries specific info for making a protein Transfer RNA (tRNA) – bonds with only one specific amino acid and carries it to the ribosome Ribosomal RNA (rRNA) – part of the structure of ribosomes and catalyzes functions during protein synthesis

Genetic Code Series of 3 nucleotides (AUG) that code for an amino acid. AUG is termed a codon mRNA has the anticodon (UAC) to bind with AUG Universal in almost all organisms

Transcription RNA is synthesized by DNA-dependent RNA polymerases Primer is not needed RNA polymerase recognizes the Promotor and Initiates transcription New RNA strand is complete after reaching a stop signal (UAA, UAG, UGA)

Transcription/Translation Has 3 stages –Initiation –Elongation –Termination

Translation Occurs in the cytosol Changing of RNA nucleotide code into amino acids.

Protein Synthesis Initiation- start of the protein Elongation-adding of nucleotides (amino acids) Termination-end of the protein

DNA Technology Gene Therapy- the use of specific DNA to treat a genetic disease by correcting the genetic problem. –Insulin - genetically altered bacteria produces the human hormone –Transgenic ‘pharm’ cows - cows that contain a human gene that codes for lactoferrin-protein in mothers’ milk that aid in immune response

GMO’s Genetically Modified Organisms. Can be any type of organism. Concern is for edible and for ‘incorporating into the wild (normal) strain. Round up Ready seeds Salmon Fish

Round up Ready Developed by Monsanto Post emergence herbicide. Kills all once germinated. –Glyphosate (RoundUp) mimics glycine and binds to the active site of EPSP synthase a critical enzyme. Plant cannot synthesize necessary amino acids.

Salmon Developed in 2010 for market but then sat in the court room for 1 year. –Worries about getting into the wild pop. –New strains have a sterile gene also inserted. Approved for markets in late 2011

Bt European Corn Borer –Dipel - natural insecticide. Dipel is a powder of freeze dried bacteria which produce a protein that is toxic to Lepidopteran insects. The larvae consume the Dipel and die. –Bt gene (cry) found in bacteria is now inserted into plants (corn, cotton, potatoes)

GMO’s Golden Rice –Rice with 2 daffodil genes and 1 bacterial gene –Production of beta carotene (provitamin A)

Microarrays Using gene tagging to locate where the gene is to make a protein Provide insight into patterns of gene expression.

Proteomics Study of the proteins coded for by your genes. Why study??? –20,000 genes = 100,000 mRNA’s = 1,000,000 proteins.

Gene Expression Factors that impact gene expression –Gender, diet, temperature, oxygen levels, humidity, light cycles, presence of mutagens all impact phenotype. –For studies of gene expression, researches must control all these variables to establish parameters. –Microarrays can provide testing on variety of variables

Gene Expression Example Emys orbicularis - Freshwater Turtle –At a specific point of development TSP- (thermosensitive period), gonadal tissue is responsive to temperature. At 25 deg. C all turtles form males, at 30 deg. C all become females. This is controlled by the Sox9 gene. –Higher temps=higher expression of Sox9 gene

Human example Data supports low dose aspirin daily for heart health. Colorectal cancer is also prevented if the patient has an allele for the gene UGT1A6 which is involved in aspirin metabolism. Slow aspirin metabolism = cancer protection. The actual mechanism is unknown