Quiz 9 Flashcards
Forensic science
Use of technology and science to help solve criminal and civil cases
DNA profiling
Identifying individuals using various types of DNA approaches (obtaining a DNA profile from a sample then comparing it another sample)
Profiling minisatellites
VNTRs are 15-100 bp long with a locus that contains up to 30 different alleles (based on how many repeats it contains); different people can have different VNTR alleles, so length of locus varies between different individuals
Method of profiling minisatellites
Extract DNA, restriction enzyme cuts om either side of the repeats, add agarose gel, and examine
Limitations of minisatellites
Requires a large amount of cells (10,000) and DNA must be fairly intact; good for paternity testing
Profiling microsatellites
STRs: each 2 to 9 bp long and repeated between 7 and 40 times; a locus; just like VNTRs different individuals have different length STR alleles at a given loci
Method of profiling microsatellites
FBI uses 20 STR loci core set; analysis is PCR based so trace samples can be used, making it choice method of DNA profiling; DNA is extracted, PCR uses primers with different colors that flank STR loci, capillary electrophoresis, analyze data using a computer to calculate size and quantity of fragments
Result: heterozygous loci make double peaks and homozygous loci single peaks
Profiling y-chromosome microsatellites
20 STR loci on the Y-chromosome that are used to ID male suspects (paternally inherited)
Limitations: can’t distinguish males with same Y-chromosome
Additional application: identify a missing person if a male relatives DNA is available for comparison
Profiling mitochondrial DNA
(mtDNA) Each human cell has 200 to 1,700 mitochondria, which are maternally inherited, so PCR to amplify portions of mtDNA, DNA sequence PCR products, and compare these DNA sequences
Useful cause only a small sample is needed, including old degraded samples, but limited because can’t tell maternal relatives apart
DNA phenotyping
Using a DNA sequence to predict phenotypes and ancestral origins by using SNP patterns to predict a suspects appearance, biological sex, geographic ancestry
Interpreting DNA profiles
Use DNA profile and compare with a sample from a crime scene or profiles in a database, and if positive match is found use statistical methods to calculate probability (more loci the better)
Issue: identical twins and close relatives
DNA profile databases
Combined DNA index system (CODIS) maintained by FBI, and some states have own databases
Limitations on DNA forensics
Most cases have no DNA evidence, in some cases DNA evidence hasn’t been analyzed, human error, crime scene samples often have mixed DNA from multiple sources, degraded DNA is difficult to analyze, criminals might introduce biological samples, DNA that matches STR loci of an individual can be synthesized
Ethical considerations of DNA forensics
Collection and storage of biological samples and DNA profiles, familial DNA testing
Genetic engineering
Changing an organism’s genome
Biotechnology
Using living organisms to create products to help improve quality of life
Biopharmaceutical products
Pharmaceutical products produced by means of biotechnology such as therapeutic proteins (most successful application of recombinant DNA tech)
Biopharming
Production of proteins in genetically modified plants and animals
Examples of biophamraceutical products
Pancreatic cells make preproinsulin, which is processed to produce mature insulin; in 1982 Genentech produced insulin in bacteria; there was an issue of bacteria not being able to process and modify eukaryotic proteins, so eukaryotic hosts were used
Bioreactors
(Biofactories) “living factories” such as goats that produce antithrombin, an antiblood clotting protein, using a vector to make it be produced in their milk, or using hens that produce egg whites containing sebelipase alfa to treat lysosomal illness
Vaccine production
Instead of just inactivated vs attenuated, genetically engineered vaccines called subunit vaccines use surface proteins from a pathogen, or DNA-based vaccines inject a plasmid with protein encoding pathogen gene to individual so the protein is expressed, causing an immune response
Using plants to produce vaccine proteins
Plants are easy to grow and cheap; ex. Express the antibodies for ebola found in mice in tobacco leaves; edible plant vaccines such as a banana or potato (cost less, easy, no needles, but difficult to determine how much a person gets, and will the vaccine pass through unaltered?)
Agricultural biotechnology
Creating transgenic plants that have desired traits; i.e. improving growth characteristics and yield, increasing nutritional value, and providing crop resistance against insect and viral pests, drought, and herbicides
Reasons for producing transgenic animals
To study gene function; development if transgenic farm animals (i.e. growth hormone to make bigger, bioreactors, protecting animals from pathogens, cow with hypoallergenic milk, CRISPR-Cas to make animals with bigger muscles, etc)
Genetically modified foods
Historically, selective breeding, but now genetic engineering more precise and faster
Plants and animals of agricultural importance whose genomes have been altered
Transgenic
Organism that contains a gene from another species
Cisgenic
Organism that contains a gene from same species
Gene-editing
Modifying an organism’s own genome without adding genes from other organisms
Herbicide resistant genetically modified crops
Herbicides kill crops of interest as well as weeds, and tillage causes erosion, so make crops that are herbicide resistant (most commonly glyphosate, which is effective at low concentrations, degrades rapidly in soil, and is nontoxic to humans)
Insect resistant genetically modified crops
Pest infestation solutions previously involved crop rotation, insecticides, and predatory organisms; now. We genetically modify crops to be resistant to insects
Bt crops
Bacillus thurigenesis produces a protein that kills insects; we genetically modify plants to carry the cry genes that produce the Cry protein
GM crops for direct human consumption
Most gm crops are used in animal feed or processed foods; but foods such as squash and papaya and golden rice have been developed for direct consumption
Golden rice
Vitamin A deficiency solved by genetically modifying rice so that it contains beta-carotene, a precursor to vitamin A; by adding two genes that encode the enzymes that allows rice to produce beta-carotene
Biolistic method
Particles of heavy metal coated with DNA, placed in a gene gun, shot into plant cells in vitro, and any cells that survive may be taken up so DNA migrated to nucleus and is integrated into a chromosome
Agrobacterium-mediated technology
Soil microbe that can infect plant cells and cause tumors thanks to the T-DNA region of its Ti plasmid; relace T-DNA with cloned gene (more successful than biolostic)
Producing roundup-ready soybeans
Glyphosate interferes with the chloroplast enzyme EPSPS to kill the plant–EPSPS from a bacterial strain CP4 is resistant to glyphosate,so but it in soybean cells using biolistic method
Producing golden rice 2
Clone three genes into T-DNA region of the Ti plasmid to encode the enzymes that facilitated the production of beta-carotene in rice grains, as well a selectable marker gene
Gene-esiting methods to produce plants and animals with new traits
ZFN, TALEN, CRISPR-Cas; organisms not considered genetically modified bc don’t contain contain genes from other organisms
GM food controversies
Health and safety (are they dangerous? How could we know so early?) and environmental effects (glyphosate resistant weeds and Bt resistant insects); genetically modified crops spreading (outcrossing: spread of transgenic from GM crops to sexually compatible non-gmo crops)
Future of GM foods
Drought, nutrient-lack, salinity, temperature resistant, animals, etc
Genetic tests:
Identify carriers of genetic conditions, predict future development of diseases, confirm a diagnosis, prenatal diagnosis, identify genetic disease in embryos
Prognostic test
Predicts liklihood of developing a genetic disease
Diagnostic
Identified a particular mutation or genetic change that causes a disease or condition
Prenatal genetic testing
Chorionic villus sampling, aka CVS, (cells derived from fetal portion of placenta using vacuum), amniocentesis (fetal cells from amniotic fluid), cell-free DNA, aka cfDNA (non-invasive, fetal DNA in mother’s blood, analyze for mutations by whole-genome sequencing)
Probe
Single stranded piece of DNA that is complementary to a portion of a gene; labeled using fluorescent dye; used to screen DNA to see if sequence that probe binds to is present in a sample–if probe is detected, sequence is present, and vice versa
Allele-specific oligonucleotides
Short DNA probes that can detect a single-nucleotide (point) mutation in a gene; can give false positive or negative results; follow up test of DNA sequencing of a PCR product can confirm
ASO testing sicke-cell anemia
Extract DNA, PCR the beta globin gene, denature PCR product and bind it to a membrane, then hybridize two separate membranes with ASOs (one with wild type and one with mutant)
ASO testing preimplantation genetic diagnosis (PGD)
Genetic analysis of a single cell in an embryo
ASO testing cystic fibrosis
Can detect deletions and insertions such as the one that causes cystic fibrosis
DNA microarrays
Need to know complex mutation patterns or previously unknown mutations; DNA microarrays are gene chips with numerous fields that each contain a specific DNA probe
Gene expression microarray
Used to examine gene expression patterns in cells or tissues such as samples from different diseases; provide info about transcription with probes name of cDNA or synthetic oligonucleotides
Gene expression in cancer
mRNA isolated from normal and cancer cells, convert mRNA to cDNA and apply to chip, and cDNAs will hybridize to complementary probes on chip; normal cells will be green and cancer cells will be red
Discoveries of gene expression in cancer
Cancers gave distinct patterns of gene expression that correlate with nature and stage, including how it responds to treatment
Gene expression microarray to learn about pathogens
New types of viruses identified regularly; learn what type of pathogen genes are important for pathogen infection and replication by infecting cells in vitro and using microarrays to examine pathogen gene expression profiles; evaluate host responses
Finding beneficial mutations
Examine genome of individuals that should have but did not develop diabetes or had immunity to many viruses
Ethical, legal, and social implications program (ELSI)
Privacy and fairness, transfer of genetic knowledge from lab to clinical practice, informed consent, improve education for professionals and public
GINA
Genetic information nondiscrimination act; designed to prohibit improper use of genetic information in health insurance and employment, but not life insurance
