Chapter 1 - Genetics and the Organism
Terms
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- Gene
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the fundamental physical and functional unit of heredity, which carries information from one generation to the next;
a segment of DNA composed of a transcribed region and a regulatory sequence that makes transcription possible - Deoxyribonucleic Acid (DNA)
-
a double chain of linked nucleotides (having dexyroibose as their sugars);
the fundamental substance of which genes are composed - Protein
-
macromolecule composed of one or more amino acid chains;
main component of phenotypic expression - Alleles
- one of the different forms of a gene that can exist at a single locus
- Genome
- the entire complement of genetic material in a chromosome set
- Diploid
- a cell having two chromosome sets or an individual organism having two chromosome sets in each of its cells
- Haploid
- a cell having one chromosome set or an organism composed of such cells
- Homologous chromosomes
- chromosomes that pair with each other at meiosis or chromosomes in different species that have retained most of the same genes during their evolution from a common ancestor
- Nucleotides
- a molecule composed of a nitrogenous base, a sugar, and a phosphate group; the basic building block of nucleic acids
- Zygote
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a cell formed by the fusion of an egg and a sperm;
the unique dipoid cell that will divide mitotically to create a differentiated diploid organism - Structural Proteins
- a protein whose function is in cellular organism structure
- Enzyme
- a protein that functions as a catalyst
- Polypeptide
-
a chain of linked amino acids;
a protein - Transcription
- the synthesis of RNA from a DNA templete
- Ribonucleic Acid (RNA)
- a single-stranded nucleic acid similar to DNA but having ribose sugar rather than deoxyribose sugar and uracil rather than thymine as one of the bases
- Transcript
- the RNA molecule copied from the DNA template strand by RNA polymerase
- messenger RNA
-
an RNA molecule transcribed from the DNA of a gene;
a protein is translated from this RNA molecule by the action of ribosomes - Translation
- the ribosome- and tRNA-mediated production of a polypeptide whose amino acid sequence is derived from the codon sequence of an mRNA molecule
- Codon
- a section of DNA, three nucleotide pairs in length, that encodes a single amino acid
- Ribosomes
-
a complex organelle that catalyzes the translation of messenger RNA into an amino acid sequence;
composed of proteins plus rRNA - transfer RNA
-
a class of small RNA molecules that bear specific amino acids to the ribosome in the course of translation;
an amino acid is inserted into the growing polypeptide chain when the anticodon of the corresponding tRNA pairs with a codon on the mRNA being translated - Introns
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an intervening sequence;
a segment of largely unknown function within a gene;
this segment is intially transcribed, but the transcript is not found in the functinoal mRNA - Exons
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any nonintron section of the coding sequence of a gene;
together, the exons correspond to the mRNA that is translated into protein - Discontinuous Variation
- variation having distinct classes of phenotypes for a particular character
- Phenotype
-
the form taken by some character (or group of characters) in a specific individual;
the detectable outward manifestations of a specific genotype - Genotype
- the specific allelic composition of a cell, either of the entire cell or, more commonly, of a certain gene or a set of genes
- Polymorphism
- the occurence in a population (or among populations) of several phenotypic forms associated with alleles of one gene or homologs of one chromosome
- Morph
-
one form of a genetic polymorphism;
may be either a phenotype or a molecular sequence - Mutant
- an organism or cell carrying a mutation
- Wild type
- the genotype or phenotype that is found in nature or in the standard laboratory stock for a given organism
- Continuous variation
- Variation showing an unbroken range of phentoypic values
- Active site
- the part of a protein that must be maintained in a specific shape if the protein is to be functional - for example, in an enzyme, the part to which the substrate binds
- Null allele
- an allele whose effect is the absence either of normal gene product at the molecular level or of normal function at the phenotypic level
- Nucleotide-pair substitution
- the replacement of a specific nucleotide pair by a different pair; often mutagenic
- Deletion
- the removal of a chromosomal segment from chromosome set
- Duplication
- more than one copy of a particular chromosomal segment in a chromosome set
- Frameshift mutation
- the insertion or deletion of a nucleotide pair or pairs, causing a disruption of the translational reading frame
- Genomics
- the cloning and molecular characterization of entire genomes
- Bioinformatics
- computational information systems and analytical methods applied to biological problems such as genomic analysis
- Probe
- Labeled nucleic acid segment that can be used to identify specific DNA molecules bearing the complementary sequence, usually through autoradiography or fluorescence
- Restriction enzymes
-
an endonuclease that will recognize specific target nucleotide sequences in DNA and break the DNA chain at those points;
a variety of these enzymes are known, and they are extensively used in genetic engineering - Southern blot
- the transfer of electrophoretically separated fragments of DNA from a gel to an absorbent sheet such as paper; this sheet is then immersed in a solution containing a labeled probe that will bind to a fragment of interest
- Northern blot
- the transfer of electrophoretically separated RNA molecules from a gel onto an absorbent sheet, which is then immersed in a labeled probe that will bind to the RNA of interest
- Western blot
- Membrane carrying an imprint of proteins separated by electrophoresis, can be probed with a labeled antibody to detect a specific protein
- Model organisms
- a species chosen for use in studies of genetics because it is well suited to the study of one or more genetic processes
- Norm of reaction
- the pattern of phenotypes produced by a given genotype under different environmental conditions
- Developmental noise
- variation in the outcomes of development as a consequence of random events in cell division, cell movement, and small differences in the number and location of molecules within cells