dna technologies

Copyright © 2005 Brooks/Cole — Thomson Learning

Biology, Seventh Edition Solomon • Berg • Martin

Chapter 14

DNA TechnologiesDNA Technologies


Biology, Seventh Edition CHAPTER 14 DNA Technologies

• Recombinant DNA methods• Restriction enzymes

–Enzymes from bacteria–Used to cut DNA molecules in specific places–Enable researchers to cut DNA into

manageable segments• Vector molecule carrier of DNA fragment

into cell• Transformation: uptake of foreign DNA

into cells



Cutting DNA with a restriction enzyme



• Splicing foreign DNA into a vector• Foreign DNA and plasmid DNA cut with

same restriction enzyme• Produces linear molecules with

complementary single-stranded ends• Recombinant DNA created by mixing so

sticky ends pair• DNA ligase forms covalent bonds, linking

the two fragments



Plasmids



• Genomic library• Collection of DNA fragments that

represent all the DNA in the genome• Chromosome library

• All the DNA fragments in that specific chromosome

• cDNA library• Produced using reverse transcriptase• Makes DNA copies of mature mRNA



Producing a genomic or chromosome library



• Genetic probes• Segments of single-stranded DNA that

can hybridize to complementary base sequences in target gene

• Southern blot technique



Using a geneticprobe to find bacterial cellswith a specificrecombinant DNA molecule



• Amplifying DNA in vitro by PCR–Small amount of double-stranded DNA–DNA precursors–Specific nucleic acid primers–Taq DNA polymerase

• DNA is denatured• Primers attach to primer-binding site on

each DNA strand• Each strand acts as template for DNA

synthesis



Amplification of DNA by PCR



• DNA sequencing• Based on chain termination method• Yields information about

–Structure of gene–Probable amino acid sequences of its

encoded proteins



Chain termination method of DNA sequencing



• Applications of DNA technology• Gene therapy• Tissue engineering• DNA typing



DNA typing



• Transgenic organisms• Foreign DNA incorporated into their

genetic material• Gene target

–Single gene inactivated or “knocked out”–“Knockout mice” used in studying genes

• Mutagenesis screening–Male mice treated with mutagens and studied



A transgenicmouse

Mouse on rightis normal; mouseon left is transgenicanimal expressingrat growth hormone



Transgenicrice

“Golden rice”shown intermixedwith white ricecontain highconcentrationsof beta-carotene



• Safety guidelines• Safety concerns

–Introduction of transgenic organisms into the environment

–Health effects on humans from consuming GM crops

• Safety measures–Special facilities designed to hold

pathogenic organisms–Science of risk assessment

dna technologies

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