Review the chemical make up of DNA

 RECOMBINATION  IN  NATURE
 
 

Changes is gene pool

Sexual Reproduction

Bacterial Transformation

Viral Infection
 

Plasmids, Restriction Enzymes, and the New Technology

Transformation in bacteria

Circular DNA

Plasmids-small circular molecules of “extra” DNA that contain a few genes.(gene which makes the the bacteria resistant to an antibiotic called ampicillin)
 

Restriction Enzymes- able to recognize and cut apart DNA t particular nucleotide sequneces
(produced by bacteria to destroy phages - does not cut its own DNA because of methyl groups)

Sticky ends

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Producing Restriction Fragments

 Enzymes make staggered cuts, some fragments have single-stranded portions (sticky ends) at both ends.
 Sticky ends- short single-stranded ends of a DNA fragment which have the chemical capacity to base-pair with any other DNA molecule that also has been cut by the same restriction enzyme.
 DNA Ligase- and enzyme that seals DNA’s sugar phosphate backbone at the cut sites, just as it does during DNA replication.
  DNA Library- collection of DNA fragments, produced by restriction enzymes, that have been incorporated into plasmids.

Gene probes locate bacteria which contain specific genes.
 

Amplification Procedures

DNA amplification- which a DNA library is copied again and again.
Cloned DNA- multiple, identical copies of DNA fragments.
Polymerase chain reaction (PCR)- method of amplifying fragments of DNA.
 Primers are synthesized.  Primers are short nucleotide sequences that base pair with any complementary sequences in DNA.
DNA polymerases- replication enzymes
PCR amplifies samples that contain even tiny amounts of DNA
 

Sorting out Fragments of DNA

 Gel electrophoresis- used to separate fragments from one another according to length.  Employs an electric field to force molecules through a viscous gel and separates them according to physical and chemical properties.
Fragments of different length can be identified by staining the gel.
 

RFLPs 
 

DNA Sequencing

 DNA fragments from a sample are sorted out according to length researchers can work out the nucleotide sequence of each type.
 

Use of DNA probes

DNA probes- short DNA sequences synthesized from radioactively labeled nucleotides.
 Nucleic acid hybridization-any base pairing between nucleotide sequences from different sources.

Probe Hybridized DNA emits radioactivity and allows you to tag the colonies that harbor the gene of interest.

Use of cDNA

cDNA- is a DNA strand “copied” from a mature mRNA transcript for the gene.
Reverse Transcription- a complementary strand is assembled on mRNA.

The modified cDNA can be inserted into a plasmid for amplification.  Recombinant plasmids can be inserted into bacterial cells.  This may use cDNA for synthesizing the protein of interest.

DNA Fingerprints

DNA fingerprint- a unique array of RFLP’s inherited from each parent in a Mendelian pattern.

RFLPs- restriction fragment length polymorphisms

Each individual of a species has a DNA fingerprint. Small molecular variations in the base sequence of the DNA of different individuals lead to identifiable differences in the restriction fragments cut form the DNA.
 

Genetic Engineering

Genes are isolated, modified, and inserted into the same organism or a different one.

Potential for research and applications in medicine, agriculture, the home, and industry.  The benefits must be weighed against the potential risks including ecological and social repercussions.

Genetically Engineered Plants

Botanist combine seeds and other living tissues from wild ancestors of potatoes, corn and other plants.

The near-absence of genetic diversity means out food base is dangerously vulnerable to many disease-causing viruses, bacteria, and fungi.

Botanist also search for good genes in the laboratories.  If cells regenerate whole plants that can be hybridized with other varieties, the hybrids may get the good gene.

Gene transfer: DNA fragments into the “Ti” plasmid , electric shock or chemicals to deliver modified DNA into protoplasts.

Improved varieties of crop plants have been developed or are in the works and plants that can serve as factories for pharmaceuticals.

Gene Therapy

Copies of normal or modified genes are inserted into an individual in order to correct a genetic defect or boost resistance to disease.