Frontiers of Frontiers of GeneticsGenetics

Chapter 13Chapter 13

Importance of bacteria Importance of bacteria in biotechnologyin biotechnology Bacteria is a very important Bacteria is a very important

organism used in DNA technologyorganism used in DNA technology Specifically Specifically Escherichia coliEscherichia coli Bacteria can easily exchange Bacteria can easily exchange

genesgenes

How can bacteria exchange How can bacteria exchange genes?genes?

Through tunnel like Through tunnel like connectionsconnections

Viruses carry bacterial genesViruses carry bacterial genes Bacteria take up DNA from Bacteria take up DNA from

surrounding environmentsurrounding environment

Recombinant DNA Recombinant DNA Technology Technology

Some Bacteria are used to mass Some Bacteria are used to mass produce specific desirable genes produce specific desirable genes and proteinsand proteins

Cutting and Pasting Cutting and Pasting DNADNA

Restriction Restriction enzymesenzymes cut cut DNA molecules at DNA molecules at specific locationsspecific locations

Fragments of Fragments of DNA spliced DNA spliced together from together from two different two different sources produces sources produces a a recombinant recombinant DNA moleculeDNA molecule

Cloning of a human gene for a hypothetical protein V

Applications of recombinant Applications of recombinant DNA technology DNA technology

Bacteria engineered to clean up toxic Bacteria engineered to clean up toxic wastewaste

Mass-production of useful chemicalsMass-production of useful chemicals Mass production of proteins and Mass production of proteins and

hormones for medical useshormones for medical uses Develop vaccines against disease-Develop vaccines against disease-

causing microbescausing microbes Develop genetically modified Develop genetically modified

multicellular organisms multicellular organisms

Genetic MarkersGenetic Markers Specific stretches of DNA that vary Specific stretches of DNA that vary

among individualsamong individuals Genetic Markers can be present in:Genetic Markers can be present in:

– Alleles for diseases or other traitsAlleles for diseases or other traits– Non-coding regions of DNA (introns)Non-coding regions of DNA (introns)

Genetic markers can help to pick out Genetic markers can help to pick out the differences between two the differences between two DNA DNA fingerprints fingerprints (particular banding (particular banding pattern produced by individual’s pattern produced by individual’s restriction fragments)restriction fragments)

Electrophoresis AnimationsElectrophoresis Animations

http://learn.genetics.utah.edu/content/labs/gel/

http://www.sumanasinc.com/webcontent/animations/content/gelelectrophoresis.html

http://www.youtube.com/watch?http://www.youtube.com/watch?v=eJe9ltcMRww&feature=related v=eJe9ltcMRww&feature=related

2. Genetic markers- particular stretches 2. Genetic markers- particular stretches of DNA that are variable among of DNA that are variable among individuals (easy way to tell if an individuals (easy way to tell if an individual is a carrier of a disease)individual is a carrier of a disease)

3. DNA fingerprints- an individual’s 3. DNA fingerprints- an individual’s unique banding pattern unique banding pattern

Control mechanisms switching genes on and Control mechanisms switching genes on and offoff

Regulation of Genes in ProkaryotesRegulation of Genes in Prokaryotes

1. 1. OperonOperon- cluster of genes and - cluster of genes and their controlled sequencestheir controlled sequences

2. 2. PromoterPromoter- control sequence on an - control sequence on an operon where RNA polymerase operon where RNA polymerase attaches to the DNAattaches to the DNA

E. coliE. coli bacteria, natural inhabitants of your intestine, break bacteria, natural inhabitants of your intestine, break down the sugar lactose. The genes that code for lactose-down the sugar lactose. The genes that code for lactose-processing enzymes are located next to control sequences. processing enzymes are located next to control sequences. Altogether, this stretch of DNA is called the Altogether, this stretch of DNA is called the laclac operon. operon.

3. 3. OperatorOperator- a control sequence that acts like - a control sequence that acts like a switch, determining whether or not RNA a switch, determining whether or not RNA polymerase can attach to the promoterpolymerase can attach to the promoter

4. 4. RepressorRepressor- a protein that functions by - a protein that functions by binding to the operator and blocking the binding to the operator and blocking the attachment of RNA polymerase to the attachment of RNA polymerase to the promoter; turns off transcriptionpromoter; turns off transcription

The The laclac operon is inactive in the absence of lactose (top) because a operon is inactive in the absence of lactose (top) because a repressor blocks attachment of RNA polymerase to the promoter. With repressor blocks attachment of RNA polymerase to the promoter. With lactose present (bottom), the repressor is inactivated, and transcription of lactose present (bottom), the repressor is inactivated, and transcription of lactose-processing genes proceeds.lactose-processing genes proceeds.

Regulation of Genes in EukaryotesRegulation of Genes in Eukaryotes

1. 1. Transcription factorsTranscription factors- proteins that - proteins that regulate transcription by binding to those regulate transcription by binding to those promoters or to RNA polymerases; are promoters or to RNA polymerases; are activated and deactivated by chemical activated and deactivated by chemical signals in the cellsignals in the cell

2. 2. Gene expressionGene expression- the transcription and - the transcription and translation of genes into proteinstranslation of genes into proteins

From Egg to OrganismFrom Egg to Organism

1. 1. Cellular differentiationCellular differentiation- when - when cells become increasingly cells become increasingly specialized specialized in structure and functionin structure and function

Though all the genes of the genome are present in every type of Though all the genes of the genome are present in every type of cell, only a small, specific fraction of these genes are actually cell, only a small, specific fraction of these genes are actually expressed in each type of cell. The yellow color indicates a geneexpressed in each type of cell. The yellow color indicates a gene that is "turned on" (expressed).that is "turned on" (expressed).

Stem CellsStem Cells

1. 1. Cells that remain undifferentiatedCells that remain undifferentiated; ; they have the potential to they have the potential to

differentiate into various types of differentiate into various types of cells; may be able to help people cells; may be able to help people with with disabling diseasesdisabling diseases

Present at a very early stage of human development, stem Present at a very early stage of human development, stem cells have the potential to develop into any type of human cells have the potential to develop into any type of human cell.cell.

Homeotic GenesHomeotic Genes

1. Master control genes that direct 1. Master control genes that direct development of body parts in development of body parts in

specific locations in many specific locations in many organismsorganisms

http://www.youtube.com/watch?v=AXjvG-FJX60 - Great transformations

The highlighted The highlighted portions of the portions of the fruit fly and fruit fly and mouse mouse chromosomes chromosomes carry very carry very similar homeotic similar homeotic genes. The color genes. The color coding identifies coding identifies the parts of the the parts of the embryo and embryo and adult animals adult animals that are affected that are affected by these genes.by these genes.