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Bio ch 12
DNA technology and the Human Genome
Terms in this set (52)
bacterial mating is not reproductive. There mechanisms of gene transfer:transformation, transduction, conjugation
the taking up of DNA from the fluid surrouding a cell
the transfer of bacterial genes by a phage. A fragment of DNA belonging to a phage's previous host cell has been accidentally packaged within the phages coat instead of phage DNA. When the phage infects a new bacterial cell, the DNA stowaway from the former host cell is injected into the new host
bacterial mating; union of cells and the DNA transfer between them; the "male" donor cell has sex pili, one which attaches to the "female" recipient cell. a cytoplasmic bridge forms between them. Donor cell DNA passes to the recipient cell. The donor cell replicates its DNA as it transfers it so the cell doesn't end up lacking any genes. The DNA replication is a special type that allows one copy to peel off and transfer into the recipient cell
once DNA is in a bacterial cell
no matter what mechanism, part of the DNA may become integrated into the recipients chromosome. Occurs by crossing over between the two DNA molecules. Results in a piece of the donated DNA replacing part of the recipients original DNA. Leaving the bacterium with a recombinant chromosome
carries genes for making sex pili and other things needed for conjugation; also contains an origin of replication where DNA replication can start; contributes to the ability of the male to carry out conjugation
F factor during conjugation
Is integrated into the male bacterium's chromosome. During conjugation, the male chromosome starts replicating at the F factors origin or replication. Growing copy peels off and heads into the recipient. Part of the F factor serves as the leading end of the transferred DNA. Rest of the factor stays in the donor cell. Recombintion can occur in the recipient cell
F factor during conjugation as a plasmid
F factor replicates and transfers one whole copy of itself, in linear rather than circular form to the recipient cell. Reforms a circle in the recipient cell and the cell becomes male. May carry genes other than those needed for replication and conjugation
a small, circular DNA molecule separate from the much larger bacterial chromosome; form of a F factor
when a transferable plasmid carries genes other than those necessary for replication and conjugation; carries these extra genes to another cell
pose serious problems for human medicine; carry genes for enzymes that destroy antibiotics such as penicillin and tetracycline.
can customize bacteria. By isolating a particular gene and inserting a piece of the DNA ontaining the gene, producing recombinant DNA, a bacterial cell takes up the plasmid by transformation and is clones to generate many copies of the gene.
the use of organisms to perform practical tasks
bacterial enzymes that act as the cutting tools for making recombinant DNA. Chop up the foreign DNA. Recognize short nucleotide sequences in DNA molecules and cut at specific points within these recognition sequences. Several hundred are known.
places where DNA is cut.
single-stranded ends of double stranded DNA fragments that result from a restriction enzyme. Form hydrogen bonded base pairs with complementary single stranded stretches of DNA
enzyme used in DNA replication but catalyzes the formation of covalent bonds between adjacent nucleotides, sealing the breaks in the DNA strands
a DNA molecule carrying a new combination of genes
Genes cloned in recombinant plasmids
Isolation of DNA from two sources, one plasmid, one favorable gene. Cut both with the same restriction enzyme. Sticky ends join by base-pairing. DNA ligase permanently bonds them together. Put plasmid into bacterium by transformation. Clone the bacterium and produce bacterial clones carrying many copies of the favored gene
the entire collection of cloned DNA fragments from a experiment in which the starting material is bulk DNA from whole cells
vectors used in cloning
bacterial plasmids and phages; with phages, the DNA fragments are inserted into phage DNA molecules. Each recombinant DNA molecule is put into a bacterial cell. It replicates and produces many new phages carrying the same foreign DNA passenger.
reverse transcriptase helps make genes for cloning
researches can focus on the genes expressed in a particular kind of cell by using mRNA for the starting material. The cells transcribe the genes and process the transcripts to produce mRNA. Isolate the mRNA and uses it as a template for synthesizing DNA by using reverse transcriptase obtained from retrovirus. Results in cDNA
result of reverse transcriptase, represents only the genes active in the starting cells. Lack introns so can be correctly transcribed and translated by bacterial cells.
nucleic acid probes identify clones carrying specific genes
a radioactive probe is added to DNA strands and tags the correct molecule by hydrogen bonding to the complementary sequence in the gene of interest
a labeled single stranded nucleic acid molecule used to find a specific gene, or other nucleotide sequence, within a mass of DNA. Hydrogen bonds to the complementary sequence in the targeted DNA
Actual procedure of using probes to find a bacterial clone carrying a gene of interest
Collection of bacterial clones growing on a nutrient medium. A piece of filer paper is pressed against the colonies, blotting cells onto the paper. Paper is treated to break open cells and separate strands of DNA, which sticks to the paper. A solution of the probe molecules is poured on the paper. Bond to any complementary DNA sequences and excess probe is rinsed off. The paper is laid on film and any radioactive areas expose the film. The developed film, autoradiograph, is compared with the master culure plate to determine which colonies carry the desired gene.
DNA microarrays test for the expression of many genes at once
isolate the mRNA made in the cells, use these molecules as templates for making cDNA molecules and then test the cDNA mixture for base pairing with DNA from different genes.
allow scientists to assay the expression of thousands of genes at once. Tiny portions of single stranded fragments are fixed to a glass slide in a grid. flourescently labeled cDNA is added. Base pairing results in floursecent DNA at the certain spot. Also called DNA chips
learn what genes are active in different tissues or in tissues in different states of health.
gel electrophoresis sorts DNA molecules by size
a sample of each mixture is placed in a well at one end. Negatively charged electrode is attached to the DNA containing end and a positive to the other. DNA molecules have a negative charge, they will move through the gel toward the positive pole. The longer DNA molecules are held back by the molecules of the gel. Move slowly and don't get as far in a given time as the shorter molecules
Restriction fragment analysis
powerful method that detects differences in DNA sequences
a chromosomal landmark whose inheritance can be studied.
mixture of DNA pieces created by extracting DNA from some of your cells and treating it with a restriction enzyme. the number of fragments and their sizes reflect the specific sequence of nucleotides in your DNA
Lengths of restriction fragments and their numbers
differ depending on the exact sequence of bases in DNA
Can use probes
to focus on the bands coming solely from the DNA sequences without having to purify them from the rest of the DNA. Restriction fragment preparation, gel electrophoresis, blotting, radioactive probe, detection of radioactivity (autoradiography)
Polymerase chain reaction
technique by which any segment of DNA can be amplified, cloned, in a test tube without using living cells
a DNA sample is mixed with the DNA replication enzyme polymerase, nucleotide monomers, and a few other ingredients. Each time replication occurs the amount of DNA doubles.
Valuable feature of PCR
can be used to copy a specific segment from within a mass of DNA. Doesn't even have to be purified. Cannot substitute for gene cloning in cells when large amounts are desired.
about 97% of the total human DNA is noncoding. Some made up of gene control sequences such as promoters and enhancers. The rest is junk DNA, we do not fully understand its function. Includes introns
much of the DNA between genes, nucleotide sequences present in many copies in the genome. 2 types
type one of repetitive DNA
a unit of just a few nucleotide pairs is repeated many times in a row. Prominant at the centromeres and ends of chromosomes.
repetitive DNA at chromosome ends, has a protective function, significant loss results in cell death
suggests this repetitive DNA plays a role in chromosome structure
may help keep the rest of the DNA properly organized during DNA replication and mitosis
2nd type of repetitive DNA
each repeated unit is hundreds of nucleotide pairs long, and copies are scattered around the genome. Associated with jumping genes
jumping genes; DNA segments that can move from one location to another in a chromosome and even from one chromosome to another. Discovered by Barbara McClintock while working with corn
movement of transposons
move by cut and paste mechanism, exit one site and insert somewhere else. Also move by copy and paste, leaving a copy behind when they move. Copy and paste method responsible for the dispersed repetitive DNA
transposons act as
natural mutagens, may help generate genetic diverstiy and thus be a significant factor in evolution
Application of DNA technology
used in fingerprinting to prove innocence or guilt in courts of law. Recombinant cells and organisms can mass produce gene products. Changing pharmaceutical industry and medicine, vaccines, treatment of disease. Genetically modified organisms
genetically modified organisms
one that has acquired one or more genes by artificial means rather than by traditional breeding methods
vector used to introduce new genes into plant cells, in nature in induces tumors in plants infected by the bacterium agrobacerium tumefaciens
an organism that contains genes from another species
alteration of an afflicted individuals genes, may someday help treat a variety of diseases
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