Genetics: Test III

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nonsense suppressors: mutations that can occur which cause premature termination of protein translation but a tRNA anticodon mutation that allows tRNA to attach to STOP codon will allow continuation of protein manufacture.
donor: the organism from which the DNA of interest is extracted.
competent: the nature of some bacteria species which readily take up foreign DNA.
transgenic organism: transformation of host DNA with DNA from a different species, NOT the same species.
restriction enzymes: act like "enzymatic scissors" and slice through DNA at specific recognizable sequences.
polygenic trait: a single phenotypic trait whose expression is controlled/affected by the action of more than one gene locus.
hybrid dysgenesis: many things wrong w/ hybrid (ex. sterility, weird mutations).
precise excision: when transposon is excised and deleted portions of adjacent DNA are restored.
checkpoints: fail-safe mechanisms that prohibit the cell to proceed to next phase until all parts of previous phase are complete.
transfection: when foreign DNA is inserted into eukaryotic genome.
DNA tumor virus SV40 (simian vacuolating virus): eukaryotic vector specific to animals, transforms normal eukaryotic cells into cancer cells.
transgenics: changing of the genome at the individual organism level.
age-dependent expression: as an organism passes through its life cycles the expression of its genes changes. Some genes are not expressed until later in life (ex. Huntington's disease, male pattern baldness, Duchenne Muscular Dystrophy).
Southern Blot: isolating and probing DNA clones.
reporter gene: used to determine whether inserted gene is "turned on" since it can sometimes be difficult to tell, detectable in phenotype when product present indicates that adjacent gene is functioning (ex. luciferase causing bioluminessence in mouse embryos & tobacco plants), a genetic marker.
DNA library: collection of cloned restriction fragments from single organism's genome.
hexosaminidase-A: responsible for breaking down lipids and in its absence sphingolipids accumulate in the developing brain and peripheral nervous system of affected fetuses/young children causing brain damage/mental impairment and death by age 5.
gain-of-function mutations: mutations in a gene that increases or changes the activity/ function of a gene product.
transformation: vectors are often mixed with bacterial strains which take them up and incorporate them into their own genomes, and replicate them during their own DNA synthesis.
highly repetitive centromerit DNA: tandem repeats in heterochromatin (untranscribed) flanking centromeres, function unknown.
autonomous elements: these can transpose by themselves (inserting this is unstable).
transposed sequences: multiple copies of small DNA segments (transposable genetic elements) which exist throughout genome, some can excise and move to other parts of genome.
apoptosis positive controls: leakage of cytochrome c from defective mitochondria acts as trigger for apoptosis.
totipotent: stem cells which can develop into entire, new organism.
apoptosis: programmed cell death, normal process by which cells are destroyed by intra- and extra-cellular mechanisms.
Human Genome Project: quest to sequence and identify function of a particular species.
resistance transfer region (RTR): regions b/w IR sections which carry antibiotic resistant genes.
retrotransposons: transposable elements that utilize reverse transcriptase to transpose themselves into DNA via an RNA intermediate (viral & non-viral retrotransposons).
pleiotropy: a single gene affects the expression of more than one phenotypic character (ex. albinism & sickle cell anemia).
protein kinases: phosphorylate specific amino acid residues on target proteins (cyclins & CDKs).
regulator gene: a gene at a completely separate locus, the product of which causes the recepetor element to move about.
receptor element: the TGE that's inserted into a gene, inactivating it.
incomplete dominance: two alleles both produce proteins but one is nonfunctional and results in a heterozygote producing only half the amount of protein as produced by a homozygous dominant individual (ex. flour color in Japanese Four o' clock flowers).
cosmids: type of cloning vector, hybrids of phage lambda & plasmids and advantageous b/c they can be used to insert somewhat large fragments of DNA (50 kb) into host cell.
maternal effect: the phenotype of the offspring depends on the genotype of the mother (ex. snail shells coiling).
microinjection: DNA injected right into nucleus of cell w/ very tiny pipette. DNA is sometimes then incorporated into host cell chromosome, done to a zygote or young embryo then implanted into surrogate mother for growth & development.
target gene: the gene that is inactivated by insertion of a transposable genetic element.
polar mutation: insertion of IS affects only transcription of genes downstream from insertion, there is directionality to the transcriptional effects.
insertion sequences (IS): first discovered in gal operon of E. coli and were physically located b/c viruses carrying bacterial gene in both mutated and wild type forms could be separated in a centrifuge; mutants had an extra piece of DNA inserted making them denser.
imprecise excision: when varying lengths of surrounding DNA are excised along w/ transposon (more common).
functional genomics: study of overall patterns of gene expression, including environment's influence.
transposon: resistance genes in the loop along w/ flanking IR sequences, can jump from one plasmid to another.
essential gene: a gene that has mutated since its demise causes death to the organism that does not get its product (ex. dwarfing gene in rabbits, yellow coat color in mice, manx allele in cats, Tay Sachs and Duchenne Muscular Dystrophy, & cystic fibrosis).
conservative: transposon is excised and reinserted elsewhere, does not leave a original copy behind.
biolistics: cells bombarded w/ microscopic projectiles (made of inert substance like tungsten or gold) and coated w/ DNA, shot at high velocity from particle gun unto cells/tissues, ideal use in live organisms and in animal cells which lack cell walls-more easily transformed than plant/fungi cells. Viruses w/ affinity for certain cell types can be used as vectors if "loaded" with desired foreign DNA and allowed to infect target host cells.
genomics: characterizing entire genome, determining sequence and eventually discovering function of all components in genome.
scavenger cells: engulf & remove the "carcasses" of cells that have undergone apoptosis.
structural genomics: study of physical nature of the genome, the physical location of genes on chromosomes.
heterozygote advantage: as it relates to sickle cell anemia, do not suffer symptoms of sickle cell anemia nor do they contract malaria since the abnormal blood cells do not provide a good environment for the protozoan parasite.
flow cytometer or PFGF (pulse field gel electrophoresis): process of storing DNA libraries, sorting nucleic acids or proteins by size.
P elements: have been useful in allowing geneticists to formulate models for the mechanisms of transposition. First discovered due to hybrid dysgenesis in offspring produced in a cross of M cytotype females and P cytotype males.
receptor tyrosine kinases (RTK proteins): activation by mitogens, initiate a signal cascade that affects the configuration of many different transcription factors, affecting gene activity in cell.
transposable genetic element: generic term to describe genetic element that can occasionally move (transpose) from one position on a chromosome to another position on same/different chromosome (aka jumping & roving genes, controlling elements, cassettes, & transposons). First discovered in corn by Barbara McClintock.
non-coding functional sequences: sequences that have no product but serve a definite function (ex. telomere sequences allow replication w/o reduction in telomere size by their affinity for telomerase).
loss-of-function mutations: mutations in a gene that eliminates or reduces the function of a wild type gene product.
neoplasia: when cell proliferation and cell death lose balance between controlling mechanisms.
epistasis: multiple genes, each with more than one allele, interact to produce unexpected phenotypes (ex. inheritance of comb shape in chickens).
pluripotent: stem cells which can develop into three germ layer cell types, but cannot give rise to entire organism.
recombinant DNA: inserting DNA from one species into another species, allow recipient species to replicate, producing multiple copies of new recombinant DNA.
Yeast Artificial Chromosome (YAC): eukaryotic vector, can carry large pieces of DNA (800 kb) to be inserted into eukaryotic cells.
multipotent: stem cells which can give rise to several cell types, limited in variety (ex. haematopoietic blood stem cells).
Western Blot: similar technique except for protein assay by antibody binding.
controlling elements: another name for receptor element & regulator gene that makes it move around.
mutable allele: a mutation that can occur in each generation due to autonomous elements b/c of its instability.
electrophoresis: process which separates molecules of different size and chemical/electrical properties, which migrate through electrically charged gel/substrate.
cDNA libraries: DNA library made up of DNA clones reconstructed from organisms mRNA molecules. mRNA is removed from living cell and reverse transcriptase is used to manufacture DNA complement sequence that can then be inserted into vector.
self-replicating episome: a bacterial genetic element capable of replicating freely in cytoplasm or being inserted into bacterial chromosome to replicate along w/ chromosome, episome called R factor.
inverted repeat (IR) sequences: create the stem loop, genes conferring drug resistance are usually located on the LOOP of the stem loop.
Long direct Terminal Repeats (LTRs): within this region the target sequence is duplicated-universal feature of all transposable element insertions, has properties reminiscent of a provirus (retrovirus that has inserted a DNA copy of itself via the activity of host's RNA transcriptase).
mitogens: polypeptide ligand signals released from a nearby (paracrine) source and received by plasma membrane receptors.
RFLPs (restriction fragment length polymorphisms): probably due to neutral mutations resulting in restriction fragments of different lengths in differing individuals. Heterozygosity of restriction fragments within single individual can be used as genetic marker, useful in studying evolutionary history of related species and used as an index of evolutionary divergence from common ancestor.
Agrobacterium tumefaciens: eukaryotic vector specific to plants, has Ti plasmid which causes gall tumors in dicot plants, can transform normal plant cell into cancerous cell if integrated into plant's DNA or used to transfer foreign DNA that can be inserted into plasmid and facilitate insertion of new genes into dicot plants based on plasmid's natural affinity.
protein phosphatases: remove phosphates from specific amino acid residues on target proteins.
Ty elements: transposable genetic elements (TGEs) in yeast and characterized by direct repeats at each end (delta elements).
apopsotsis negative controls: proteins like Bcl-2 and Bcl-x block release of cytochrome c and possibly stabilize mitochondrial membrane preventing its rupture, maintains apoptosis system in "off" mode.
R factor: for "Resistance," transferred rapidly b/w bacteria upon conjugation and exists as plasmid in cytoplasm.
nonautonomous elements: need input (enzymatic product) of a separate element in order to transpose (inserting this is stable).
expression libraries: comprised of expression vectors (cloning vectors that contain the required regulatory elements for gene expression, such as promoter region).
sex-dependent gene expression: in sex influenced traits, expression varies depending on the sex of the individual carrying the alleles (ex. finger length, feathering morphology in chickens).
dispersed gene families: gene family which codes for a particular type of protein/product and found through out genome, can include members that no longer code for a functional product (pseudogene).
DNA clone: identical pieces of DNA derived from a single source.
vector: the DNA into which the DNA of interest is inserted (ex. bacterial plasmid).
in vitro mutagenesis: when the sequence of the wild type gene is known but not its function, this process can be used to destroy the type gene's function in controlled fashion so the effect on mutant organisms can be studied.
expressivity: the degree to which a particular genotype is expressed in the phenotype of a particular individual, 'what happens in a particular individual' (ex. neurofibromatosis).
ORF ("open reading frame"): segment of DNA flanked by a start and stop codon, though it has been sequenced its products and function are unknown (putative gene).
copia-like elements: scattered throughout genome and code for many mRNAs found in Drosophila.
restriction fragments: DNA that is cleaved by restriction enzymes and can be isolated through electrophoresis.
teratogenesis: formation of birth defects due to environmental agents (ex. viruses, chemicals, etc...)
electroporation: if a host has cell walls enzymes are used to dissolve walls, leaving only protoplast (cell w/o walls). Proplasts exposed to short electrical pulse that opens transient membrane channels through which DNA can pass, transformed cells can then be cultured in media to allow reformation of cell walls and normal growth into whole organism.
cyclical variation: phosphorylation/dephosphorylation of these key proteins determine which ones are active for each portion of cell cycle.
recombinant DNA technology: the recombinant DNA is made by splicing a DNA fragment of interest into a small, fast replicating molecule (ex. bacterial plasmid) that may also be used to deliver DNA to target location in host.
autoradiograph: image taken on radiography film in which exposure is made by radioactivity present in the sample itself.
Sanger/Dideoxy Method: determination of the actual base sequence in a DNA segment. After dideoxy binding and formation of Sanger sequence gel by electrophoresis there will be a huge number of DNA fragments, each one nucleotide longer than last.
spacer DNA: apparently not transcribed, but not certain, unknown function.
tandem gene family arrays: genes which code for a product needed in great quantities in cell and arranged in adjacent repeats along chromosome (ex. Nucleolar Organizer regions)
monogenic trait: a single phenotypic trait whose expression is controlled by the action of a single gene locus.
replicative: transposon is copied and inserted elsewhere, leaving the original in its place.
genomic library: DNA library containing organism's complete genome in form of small DNA fragments (oligonucleotides) representing known genes.
congruent protein mutations: if one protein suffers from a mutation that changes its shape (and thus its activity w/ another protein) this can be overcome if the protein mate also undergoes a mutation which makes the two of them work together again.
genetic probe: radioactively labeled nucleic acid fragment of known sequence that allows precise location of complementary DNA sequence. DNA of interest is denatured and probe is allowed to anneal w/ complementary regions.
proto-oncogene: non-mutant form of an oncogene.
Norm of Reaction: the degree to which phenotype varies w/ environmental influence.
phenocopies: an environmental factor can mimic the effect of a mutation if the factor is present during a critical point during development (ex. presence of rubella, thalidomide babies).
codominance: two alleles of the same gene are expressed and both products are functional, though different (ex. human ABO blood groups).
recombinant DNA molecule (chimeric DNA): essentially a vector molecule with an insert of foreign DNA.
Polymerase Chain Reaction (PCR): rapid, efficient amplification of DNA sequences of particular interest.
bioinformatics: use of computers to store and analyze genetic data like DNA libraries.
transgenic: a type of organism containing an artificially inserted, foreign piece of DNA.
Northern Blot: similar technique except for RNA assay.
VNTRs (Variable Number Tandem Repeats): 1-5 kb long, function unknown but highly variable among individuals, these fragments of DNA are used as DNA fingerprints in criminal forensics.
complementation test: knowing the location of a mutation within a particular organism in order to study the contribution of various genes to a particular trait or biological process (ex. petal color in harebells).
proteome: all genes within genome that code for proteins.
oncogene: a dominant mutant gene that contributes to formation of animal cancer.
pseudogene: a "non-functional" mutant leftover.
caspases: disrupt structural & functional systems of target cell.
cloning vectors: foreign DNA introduced into cells w/ a vector/cloning vehicle, depends on type of tissue and purpose of intent.
unstable mutant allele: an allele where mutations occur at a very high rate.
penetrance: proportion of individuals with a specific genotype manifest that genotype at a phenotypic level, 'what happens in a population' (ex. brachydactyly in humans).
FB elements: contain numerous inverted repeats, insertion of FB elements has shown to cause several types of unstable mutations in Drosophila.
functional complementation: genes of interest can be located for cloning through their ability to restore wild type phenotype to a mutant organism.
genetic dissection: involves the intentional disruption of wild type alleles in study organisms and study of the effect the mutation has on the organism's phenotype.

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