exam3 - Exam 3 lecture 18-breeders choose plants and...

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Exam 3 lecture 18 -breeders choose plants and animals with the most desired traits to serve as parents of the next generation -selective breeding requires time, patience, and several generations of offspring before the desired trait becomes common in a population -increasing the frequency of desired alleles in a population is the essence of genetic technology Inbreeding develops pure lines -inbreeding is the mating between two closely related individuals -it results in offspring that are homozygous for most traits. -can bring out harmful recessive traits -horses and dogs are inbred to make pure lines hybrids - bigger and better -hybrid is the offspring of parents that have different forms of a trait -produced by crossing 2 purebred plants, are often larger and stronger than their par- ents Genetic engineering -a faster and more reliable method for increasing the frequency of a specific allele in a population -this method involves DNA from one organism into small fragments and inserting the fragments into a host organism of the same or different species What can we do with the DNA in the lab? -extract DNA from cells -Cut DNA into small fragments (restriction enzymes) -spread the fragments out on a gel by size -identify the fragments of interest (molecular probe) -clone a gene or any fragment of DNA -sequence the DNA -Make transgenic organisms Recombinant DNA technology -techniques in which DNA fragments are linked to self replicating vectors to create re- combinant DNA molecules which are replicated in a host cell What is needed to clone DNA? -a way to cut DNA at specific sites (restriction enzyme) -a carried molecule to hold DNA for cloning (vector) -a place where the DNA can be cloned or copied (host cell)
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Extracting DNA -Lyse cells -Precipitate the DNA (cold EtOH) -Isolate the DNA and wash it. -Objective: clean high molecular weight DNA DNA can be cut at specific sites using restriction enzymes -bacteria produce restriction enzymes to protect themselves from viral infections -restriction enzymes are bacterial proteins that have the ability to cut both strands of the DNA molecule at a specific nucleotide sequence - the scissors doing the cutting Restriction enzymes cleave DNA -the same sequence of bases is found on both DNA strands, but in opposite directions (a palindrome) -sequences form sticky ends: singe stranded ends that have a tendency to join with each other (the key to recombinant DNA) or blunt ends that don’t allow the tendency to join with each other. Vectors are carriers of DNA to be cloned - linking DNA segments produced by restriction enzymes with vectors gives rise to re- combinant DNA -Enzyme ligase does the job (the glue) Vectors transfer DNA -vector is the means by which DNA from another species can be carried into the host cell -may be biological or mechanical -biological vectors include viruses and plasmids -a plasmid is a small ring of DNA found in a bacterial cell Mechanical vectors to transfer DNA -Two mechanical vectors carry foreign DNA into a cell’s nucleus -
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