Peter J. Russell Preface This page intentionally left blank Genetics: An introduction Key Questions • What are the major subdivisions of genetics? Sylized. Peter J. Russell - Free download as Powerpoint Presentation .ppt), PDF File Download as PPT, PDF, TXT or read online from Scribd . Peter J. Russell, iGenetics: Copyright © Pearson Education, Inc., publishing as Benjamin Cummings. THIS IS AN E-BOOK = DIGITAL BOOK AVAILABLE IN PDF, MOBI, EPUB and KINDLE VERSIONS. ONLY EMAIL DELIVERY. NO SHIPPING!! NOT THE.
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Peter J. Russell has 52 books on Goodreads with ratings. Peter J. Russell's most popular book is iGenetics: A Molecular Approach. Study iGenetics: A Molecular Approach (3rd Edition) discussion and chapter questions and find iGenetics: A Molecular Approach (3rd Edition) Peter J. Russell. Download iGenetics by Peter J. Russell PDF free. The “iGenetics: A Molecular Approach (3rd Edition)” is a great book for any BSc student of the.
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Russell epub iGenetics: A Molecular Approach , pdf Peter J. A Molecular Approach , the book iGenetics: Russell ebook iGenetics: A Molecular Approach Book, pdf iGenetics: A Molecular Approach , Read iGenetics: A Molecular Approach Ebook , iGenetics: A Molecular Approach Ebooks, iGenetics: A Molecular Approach pdf read online, iGenetics: Prenatal diagnosis uses amniocentesis or chorionic villus sampling to assess risk to the fetus of a genetic disorder by analyzing for a specific mutation, or biochemical or chromosomal abnormalities.
Genetic testing can determine the result of a particular conception. Genetic testing may be used during in vitro fertilization to eliminate before implantation embryos with mutated genes that could result in serious disease. Examples of tests for specific mutations using blood from newborns include: Phenylketonuria PKU.
Carrier detection tests using blood samples are available for many genetic diseases, including: Tay-Sach disease. Duchenne muscular dystrophy a disease of progressive muscle atrophy and disfunction. Testing by restriction fragment length polymorphism RFLP analysis detects loss or addition of a restriction site in the region of a gene. The restriction map is independent of gene function, so RFLPs may occur without changing the phenotype.
In heterozygotes both parental types are seen, allowing easy detection of carriers. RFLPs are associated with many genetic disorders. Sickle-cell anemia is an example: A single base-pair change in the b-globin gene results in abnormal hemoglobin, Hb-S, rather than the normal Hb-A.
Hb-S molecules cause sickling of red blood cells. The Hb-S mutation is an AT-to-TA base pair change in the 6th codon of b- globin, resulting in a valine rather than a glutamic acid, and also eliminating a DdeI restriction enzyme site Figure 8.
This difference can be detected using Southern hybridization of genomic DNA with a b- globin gene probe.
RFLPs associated with genetic disorders may also result from changes in flanking sequences. PKU is an example: PKU results from defective phenylalanine hydroxylase enzyme. Recombination events that occur between the site of the RFLP and the gene mutation can complicate this test.
Polymerase Chain Reaction 4. It requires sequence information so that specific primers can be designed. An example is allele-specific oligonucleotide ASO hybridization used to detect mutations in GLC1A, a gene involved in maintaining normal eye pressure.
Abnormal pressure in the eye results in glaucoma, which can cause blindness. Mutations in GLC1A can be responsible for this condition.
Sequence of GLC1A is known, and glaucoma-inducing mutations identified. PCR primers were designed to amplify a region of the gene where glaucoma-inducing mutations occur. PCR products undergo agarose gel electrophoresis, are extracted from the gel and dotted onto duplicate membrane filters, and denatured to single strands. One blot is probed with a labeled oligonucleotide specific to the wild-type allele, while the other receives labeled oligo specific for a particular mutation.
A related PCR procedure uses labeled PCR product as a probe against a filter blotted with an array of normal and mutant alleles of the gene. The dot s to which the probe binds indicate the genotype of the individual. Genetic testing is not available for every disorder. Reasons include: Lack of information about the gene. Its location may be unknown, or it may not yet be sequenced.
Many different mutations in the gene result in disease, so a single molecular test is of little use. An individual maybe tested for the presence of a known subset of mutations, but a negative test does not guarantee the absence of a deleterious allele.
Not every individual carrying a disease-associated mutation develops that disease, and so genetic testing is of limited use, and is usually performed only in high-risk families. Locating a gene is relatively easy when its gene product is known. Because positional cloning involves identifying a gene without knowing its product, it is sometimes called reverse genetics. Cystic fibrosis CF , the most common lethal genetic disease in the U.
Its gene was the first to be isolated solely by positional cloning. Two were found that flank the CF gene, localizing it to region 7qq32 7 is the chromosome, q is the long arm, indicates subregions. The DNA region of the CF gene was cloned using chromosome walking to identify adjacent chromosomal fragments from clones in a genomic library.
Figure 8. The end of a known sequence is used as a probe to find an adjacent fragment. The end of that DNA is then used to find the next fragment, and so on. Repetitive DNA sequences can complicate chromosome walking. The length of each step in the walk is limited to the size of the inserts in the library, minus the size of the overlap.
Chromosome jumping was also used in isolating the CF gene. It is similar to chromosome walking, but eliminates the need to detect overlapping regions Figure 8.
Partial restriction digestion produces large overlapping DNA fragments. Fragments arc circularized with DNA ligase, bringing ends that were some distance apart together. Resulting circles are cut to release the junction region, which is cloned to form a jumping library.
When a probe detects a homologous DNA in the library it will be associated with DNA from some distance away in the chromosome. The associated DNA is then used as a probe to make another jump in the library, or as the starting point for chromosome walking. Identifying a gene of interest in a set of clones is a challenge.
Cloned DNA was used as a probe against genomic DNA of other species, because genes are likely to be more conserved than nongene sequences. Genomic fragments from a variety of species were analyzed by Southern hybridization a zoo blot.
DNA probes from genes are expected to hybridize with mRNAs in a Northern, and this technique can test whether a sequence is transcribed. This probe identified a single cDNA clone by Northern blot, and that clone was then used to find the genomic CF sequences. Isolation of the CF gene was confirmed when DNA sequences in this region proved to be different in a normal and a CF individual, showing a deletion of 3-bp in the CF patient. Computer analysis of the CF gene predicts that the CFTR cystic fibrosis transmembrane conductance regulator protein has two similar membrane- association motifs, and an ATP binding domain.
The common CF mutation removes phenylalanine from the 1st predicted protein domain. Relevant molecular markers include: RFLPs detected by restriction digestion and blotting. PCR product polymorphisms detected by agarose gel electrophoresis. Alleles detected by allele-specific oligonucleotides ASOs.
Highly polymorphic DNA regions are preferred for typing, and great variation is shown in regions of DNA consisting of short tandem repeats: Microsatellites, also called single tandem repeats STRs , have repeating units of 2—4 bp b. Minisatellites, also called VNTRs variable number of tandem repeats , have repeating units ranging in size from 5 to a few tens of base pairs. The size variation is detected by probing for the particular repeat sequence. The probe may be specific for STR or VNTR sequences at one genomic locus a monolocus or single-locus probe or at a number of loci a multilocus probe.
Combing Through "Fur"ensic Evidence. DNA typing in a paternity case would proceed as follows Figure 8. DNA samples typically from blood are obtained from mother, baby and putative father. DNA is cut with a particular restriction enzyme, electrophoresed and transferred to a membrane filter by Southern blotting. Baby and mother are expected to share one allele, while baby and father share the other allele.
If the man and baby do not share a common allele, DNA typing has proved he is not the father. If they do share an allele, paternity is possible, but not proven, since other men also carry the allele at some frequency that can be calculated. Often five or more different polymorphisms are characterized. If all match with the putative father, the combined probabilities calculated for the array of polymorphisms can be convincing evidence in court. The role of DNA typing in court cases is still being determined, and DNA typing is not generally accepted for proving parenthood or guilt, although it is widely used as evidence of innocence.
DNA evidence is most commonly rejected for procedural reasons, such as errors in evidence collection or processing, or due to lack of population statistics for the alleles in question. Examples of DNA typing used to analyze present-day samples include: Forensic analysis in criminal cases. Population studies to determine variability in groups of people. Proving horse pedigrees for registration purposes. Forensic analysis in wildlife crimes, allowing body parts of poached animals to be matched and used as evidence.
Detection of pathogenic E.