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Genetics_CH1
introductory terms
| Question | Answer |
|---|---|
| genetics | the study of all aspects of genes (both molecular genetics and genomics) |
| genes | the fundamental units of biological information (virtually all of these are composed of DNA) |
| molecular genetics | studies genes one or few at a time (began after the discovery of DNA) |
| genomics | the study of complete gene sets |
| genomes | complete gene sets |
| zygote (single cell) | fertilized eggs |
| chromosomes | worm-shaped, densely staining bodies found within the nuclei of cells, pass from generation to generation through nuclear divisions called meiosis and mitosis |
| DNA | discovered in the 1950s by James Watson and Francis Crick, contains information written in a genetic code (passed from generation to generation) |
| gentic code | a linear series of four molecular building blocks called nucleotides |
| double helix backbones | made of sugar-phosphate |
| genome | each copy of the identical complementary chromosome that is in a cell's nucleus |
| chromosome | are in pairs and each is one, long DNA molecule |
| genes | functional regions of the DNA |
| DNA | double helix in structure |
| DNA molecule | made up of two long molecular strands of nucleotides wound around each other in a double helix |
| nucleotides | four kinds in DNA, each has a deoxyribose sugar, a phosphate group and a nitrogenous base (sugars and phosphates are identical, but the nitrogenous bases vary) |
| nitrogenous bases | adenine (A), thymine (T), guanine (G), and cytosine (C) (AT CG = pairs) |
| each strand | sugar and phosphate groups form the chain and the bases face the center (hydrogen bonding connects bases) |
| genome | an organism's complete set of genetic information, encoded in its DNA |
| eukaryotes | organisms whose cells have nuclei |
| individual chromosome | just one side of the double helix |
| diploid | the nuclei contain two complete copies of the genome and so two identical chromosome sets (2n) |
| haploid number | the number of chromosomes in the basic genomic set (n) |
| homologous chromosomes or homologs | the two members of a chromosome pair (in a diploid organism) |
| homologous pairs | virtually the same, even though minor variation in the nucleotide sequence is often present |
| genes | segments along one continuous DNA molecule (the basic carrier of information) |
| exon | coding region |
| intron | internal noncoding inserts that are part of the functional coding sequence of genes |
| 5' --> 3' | the direction of transcription of genes |
| gene pair | in diploids, the presence of genes (because of homologous chromosomes) |
| somatic | cell that is part of the body |
| electrophoresis | a way to separate DNA molecules by size on a gel (number of DNA bands = haploid number) |
| nucleosomes | molecular spools that the DNA double helix coils around (in order to become extremely tightly packed) |
| histones | eight proteins contained in each nucleosome |
| scaffold | helps organize the 3-D structure of a chromosome |
| chromatin | DNA and associated nucleosomes (together) |
| centromere | a constricted region of a chromosome that acts as an attachment point to move the chromosome during cell division |
| telomeres | the tips of the chromosome (prevent DNA from fraying... like plastic bands on shoelaces) |
| mitochondria | contain a small fraction of the DNA in eukaryotic genomes |
| chloroplasts | contain DNA in plant species |
| extranuclear genome | DNA stored outside the nucleus, such as in chloroplasts or mitochondria |
| prokaryotes | lack nuclei |
| cytoplasm | where the genome resides unbounded in prokaryotic organisms |
| plasmids | small circular chromosomes in prokaryotes (in addition to chromosome) |
| virus DNA | small and usually linear |
| proteins | responsible for the form or physical essence of an organism |
| structural proteins | contribute to outward physical structure such as hair, nails, and muscle and also to structural elements within the cell such as the cytoskeleton |
| enzymatic proteins | catalyze the reactions going on within cells, reactions that make all the main types of molecules, including proteins themselves, nucleic acids, carbohydrates, and fats |
| regulatory proteins | act to turn on or turn off gene activity at the appropriate time and place |
| main task of the living system | convert the information of the DNA of genes into proteins |
| first stage of protein synthesis: transcription | the DNA of a gene is copied to make another linear molecule calle ribonucleic acid (RNA) |
| RNA | composed of nucleotides, but the sugar is ribose and the base uracil replaces the base thymine, single stranded |
| RNA transcript | modified and the introns are removed (in eukaryotes) |
| messenger RNA (mRNA) | the final form of gene transcripts destined for protein synthesis |
| mRNA | transported to the cytoplasm for translation into a polypeptide chain |
| DNA --> RNA --> protein | mRNA translates into proteins |
| reverse transcription | RNA can go back to DNA in order to maintain the telomeres that form the chromosome tips |
| protein | long strand of amino acids called polypeptides (20 amino acids in cells, and various combinations of these 20 give each protein its specific shape and function) |
| codons | groups of three nucleotides that constitute three-letter "words" of the genetic coding language |
| RNA molecules | never translated into protein |
| ribosomal RNA (rRNA) | part of ribosomes |
| transfer RNA (tRNA) | carry amino acids to the translational system |
| DNA replication | two daughter chromosomes are created, both with a new and old strand |
| gamete | sex cell |
| mutation | a change to the DNA sequence |
| epigenetic | nongenetic changes such as certain environmentally induced chemical changes in histones that are self-perpetuating, and alter the gene function which is handed down to descendants |
| natural selection | the process whereby individuals with a particular characteristic may reproduce better than others in a given environment thereby producing more individuals with that particular characteristic (discovered by Charles Darwin and Alfred Russel Wallace) |
| homology | similarity due to shared ancestry from a common ancestor |
| theory of evolution | natural selection produces homology |
| evolutionary tree | a treelike branched diagram that shows the descent of various modern and fossil species through intermediate ancestral forms over time (species with similar DNA are closer on the tree) |
| model organisms (fruit fly, mice, E. coli, and baker's yeast) | living beings that have properties that lend themselves well to an investigation (biological), and living beings that are easy and cheap to maintain and grow quickly (expediency) |
| transgene | a foreign gene that can be introduced into an organism |
| transgenic organism | an organism that has a foreign gene |
| gene therapy | correcting genomes at the DNA level |
| DNA fingerprint | based on the observation that certain regions of the genome are found in multiple adjacent copies (repetitive DNA), & the number of copies at any chromosomal position is highly individualistic-comparison of several-such sites reveals personal fingerprint |
| eugenics | improving the quality of human births |
| forward genetics | treat cells of the normal wildptype form of the organism w/ agents such as X rays or chemicals that causes mutations-screen descendants 4 abnormal manifestation of the function in question-Ask r properties inherited as 1 mutated gene & determine function |
| forward genetics | Mutation --> gene discovery --> DNA sequence and function |
| reverse genetics | starts with a gene sequence (probably learned from a genome sequence) that has no known function and then attempts to find that function |
| directed mutagenesis | experimental approaches that can target mutations to an individual gene |
| reverse genetics | Gene (DNA sequence) --> mutation --> function |
| DNA manipulation | usually focuses on parts of the genome |
| DNA cloning | taking a DNA fragment and replicating it many times over until there are many copies so that essentially it can be treated like a reagent in a test tube |
| amplifying | the process of replicating a DNA sequence |
| cut DNA sequence | use enzymes |
| vector (carrier) | small DNA fragments are inserted into this small self-replicating chromosome |
| bacterial cells | divide with vectors inside them causing the vectors to replicate |
| probing | method of detecting spec. macromolecules in a mixture- uses of the specificity of intermolecular binding (the binding affinity of mRNA 2 the DNA sequence from which it was transcribed)- probe will only bind w/ the sought-for macromolecule & is labeled |
| probe | works because of base complementarity... nucleotide sequence is complementary to its target |
| probing | must be done with separated DNA strands so that the bases are unoccupied |
| Southern blot | DNA is cut using enzymes and then put onto a porous membrain where they travel by size |
| probe | introduced after blotting to bind to specific piece of complementary DNA |
| microarray | postage-stamp-size glass where DNA fragments representing all the genes of a genome are placed |
| probes - microarray | made by converting mRNAs from one tissure (such as cancer) to DNA called cDNA... microarray is bathed in this probe and spots of the label on the glass reveal which genes were being transcribed in the sample tissue |
| Polymerase Chain Reaction (PCR) | using a sequenced region, it is possible to detect homologs of that region in an unknown sample using this method |
| PCR | requires inspection of the genome sequence and picking two short single-stranded DNA segments (primers... initiate DNA replication across a region) that flank the region in question |
| PCR | replication process shuttles back and forth across the region, with each synthesized copy acting as the template for a new round of synthesis (process expands exponentially giving multiple copies of that DNA segment |
| PCR | primers will only work if the target region in question (including the primer sequences) contains a homolog |
| Northern blot - probing for specific RNA | uses mRNA extracted from the tissue, separated into fragments of different sizes using electrophoresis, and blotted onto a membrane (cloned gene is used as a probe, and its label will highlight the mRNA in question if present) |
| Western blot - probing for a specific protein | protein mixture is separated n2 bands of distinct proteins by electrophoresis & then blotted onto membrane- specific protein revealed by bathing the membrane in a solution of antibody obtained from a host into which the antigen was previously injected |
| antibody | a protein made by an animal's immune system; it binds with high affinity to a molecule such as a specific protein (which acts as an antigen) |
Created by:
Nicolekr
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