Biology 105 Chapter 13 Gene Expression Pages 282

Biology 105 Chapter 13: Gene Expression Pages 282 -306

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

Student Outcomes l Explain how mutations occur l Describe several genetic disorders

Gene Expression l Series of steps where DNA specifies the makeup of the cell’s proteins. l One-gene, one-enzyme: DNA (genes) code for one enzyme or one protein. l 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 (m. RNA) – carries specific info for making a protein Transfer RNA (t. RNA) – bonds with only one specific amino acid and carries it to the ribosome Ribosomal RNA (r. RNA) – part of the structure of ribosomes and catalyzes functions during protein synthesis

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

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

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

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

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

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

Salmon l 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 l 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 l Golden Rice – Rice with 2 daffodil genes and 1 bacterial gene – Production of beta carotene (provitamin A)

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

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

Gene Expression l 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 l 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 Sox 9 gene. – Higher temps=higher expression of Sox 9 gene

Human example l Data supports low dose aspirin daily for heart health. Colorectal cancer is also prevented if the patient has an allele for the gene UGT 1 A 6 which is involved in aspirin metabolism. Slow aspirin metabolism = cancer protection. l The actual mechanism is unknown