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168 Cards in this Set
- Front
- Back
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Recombination
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Formation of new genetic combinations by exchange of parts between homologs
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Linkage
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When two loci recombine at less that 50% of gametes
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Chi-Square Test
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A statistical method for testing the fit between observed and expected data
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Chiasma
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Structure formed at the spot where crossing-over occurs between homologs
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Tetratype
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A tetrad carrying four kinds of haploid cells; two different parental classes, and two recombinants
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Locus
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The relative chromosomal location of a gene
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Coefficient of Confidence
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The ratio of observed double-crossovers to expected crossovers
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Interference
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One crossover along a chromosome makes a second one nearby less likely
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Parental ditype
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An Ascus containing only two non-rcombinant kinds of spores
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First-order segregation
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When two alleles of a gene are separated into different cells at the first meiotic division
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ascospores
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Fungal spores contained in a sac
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mosaic
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Individual composed of cells with different genotypes
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Transformation
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Griffith Experiment
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Pyrimidine
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A nitrogenous base containing a single ring
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Dexyribose
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The sugar within the nucleotide subunits of DNA
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Hydrogen bonds
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Noncovalent bonds that hold the strands of the double helix together
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Complementary bases
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Two nitrogen bases that can pair via hydrogen bonds
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Origin
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A short sequence of bases where unwinding of the double helix for replication begins
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Okazaki fragments
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Short DNA fragments formed by discontinuous replication of one of the strands
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Purine
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A nitrogenous base containing a double-ring
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Topoisomerases
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Enzymes involved in uncoiling DNA
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Semiconservative replication
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Meselson - Stahl Experiment
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lagging strand
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The strand that is synthesized discontinuously during replication
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telomeres
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Structures at ends of eukaryotic chromosomes
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Transition
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Substitution that exchanges a purine for a purine (A ↔ G) or a pyrimidine for a pyrimidine, (C ↔ T)
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Base Substitution
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replacement of a single base nucleotide with another nucleotide
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Transversion
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Substitution that exchanges a purine for a pyrimidine or a pyrimidine for a purine (C/T ↔ A/G)
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Inversion
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180-degree rotation of a segment of the DNA molecule
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Translocation
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large-scale mutations in which part of one chromosome becomes attached to a nonhomologous chromosome
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Deletion
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the loss of a segment of the genetic material from a chromosome
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Insertion
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the gain of a segment of new genetic material into the a chromosome
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Deamination
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Hydrolysis changes a normal base to an atypical base containing a keto group in place of the original amine group.
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X-ray irradiation
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Substitution that exchanges a purine for a pyrimidine or a pyrimidine for a purine (C/T ↔ A/G)
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Intercalator
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Molecules that can sandwich between base pairs, disrupting ordering
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Unequal crossing-over
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crossing over between nonallelic sequences on nonsister chromatids in a pair of homologues.
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codon
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A group of three mRNA bases signifying one amino acid
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colinearity
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Linear sequence of amino acids in the polypeptide corresponds to the linear sequence of nucleotide pairs in the gene
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reading frame
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The grouping of mRNA bases in threes to be read as codons
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degeneracy of genetic code
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Most amino acids are not specified by a single codon
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nonsense codon
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Stop codons - UAA, UGA, UAG
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initiation codon
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AUG in a particular context
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template strand
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The strand of DNA having the base sequence complementary to that of the primary transcript
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transcription
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The conversion of DNA-encoded information to its RNA-encoded equivalent
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intron
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A sequence of base pairs within a gene that is not represented by any bases in the mature mRNA
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Reciprocal Translocation
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Exact exchange of parts of two non-homologous chromosomes
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Gynandromorph
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organism that contains both male and female characteristics
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Pericentric
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chromosome rearrangement that includes the centromere
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Paracentric
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inversions that do NOT include the centromere and both breaks occur in one arm of the chromosome
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Euploids
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having complete sets of chromosomes
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Polyploidy
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having more than two sets of homologous chromosomes
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Transposition
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Movement of short DNA elements
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Aneuploids
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state of not having euploidy
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Deficiency
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When a Block of one of more nucleotide pairs is lost from a DNA molecule
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Base Analogs
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Mutagens that are similar enough in chemical structure to the normal nitrogenous bases that they can be incorporated into DNA in place of normal bases
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Acrocentric
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A chromosome in which the centromere is close to one end
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Allele Frequency
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The proportion of all copies of a gene in a population that are of a given allele type
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Allosteric proteins
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Proteins that undergo reversible changes in conformation when bound to another molecule
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Anaphase
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The stage of mitosis in which sister chromatids are separated and pulled to opposite spindle poles
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Anaphase I
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Phase of Meiosis I in which the chiasmata joining homologous chromosomes dissolve, allowing parental homologs to move toward opposite spindle poles
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Anaphase II
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Phase of Meiosis II in which coheson joining sister chromatids is removed, allowing sister chromatids to move toward opposite spindle poles
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Ascus
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Saclike structure in some fungi that houses all four haploid products of meiosis
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Attenuation
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A type of gene regulation in which transcription of a gene terminates in the regulatory region before a complete mRNA transcript is made
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Autotroph
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An organism that is nutritionally self-sufficient, e.g. plants produce their own food by photosynthesis
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Auxotroph
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A mutant microorganism that can grow on minimal medium only if it has been supplemented with one or more growth factors not required by the wild-life strain
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Bacteriophage (Phage)
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A virus that attacks bacteria
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Biochemical Pathway
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An orderly series of reactions that allows an organism to obtain simple molecules from the environment and convert them step-wise into successively more complicated structures
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Bivalent
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A pair of synapsed homologous chromosomes during prophase of meiosis I
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Catabolite repression
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Repression of expression in sugar-metabolizing operons like the lac operon when glucose or another preferred catabolite is present
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Centromere
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Region of chromosome at which sister chromosomes are connected
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Chiasmata
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Observable regions in which non-sister chromatids of homologous chromosomes cross over.
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Chromosome
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Self-replicating genetic structure of cells that carries a linear array of genes in its nucleotide sequence
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Codominant
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Expression of heterozygous genotype resulting in hybrid offspring that resemble both parents equally for a particular trair
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Codon
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Nucleotide triplet that represents an amino acid to be inserted in a specific positionin the growing amino acid chain during translation
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Conjugation
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A mechanism of gene transfer in bacteria in which a donor connects to a recipient using a pilli, and transfers genetic material through the pilli.
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Constitutive expression
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A state of gene activation that remains at constant high level and is not subject to repression
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Criss-cross inheritance
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Inheritance pattern in which males inherit a trait from their mothers, while daughters inherit the trait from their fathers
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Cross
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The deliberate mating of selected parents based on particular genetic traits desired in the offspring
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Crossing over
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During Meiosis, the breaking of one maternal and one paternal chromosome, resulting in the exchange of corresponding sections of DNA and the rejoining of the chromosome. Can result in the exchange of alleles between chromosomes
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Dihybrid
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An individual that is heterozygous for two genes
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Thymine Dimer
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Bonding between two adjacent Thymines in a nucleotide sequence
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Alleles
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Alternatives forms of a single gene
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Complementation test
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Method of discovering whether two mutations are in the same or separate gene
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Dominant allele
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An allele that expresses its phenotype in a heterozygote
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epistatis
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When an allele hides the effects of another allele on the same gene
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expressivity
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The degree to which a genotype is expressed in a phenotype
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F plasmid
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A conjugative plasmid that carries many genes required for the transfer of DNA
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F⁺ plasmid
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Cell carrying the F plasmid
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F⁻ plasmid
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Cell without the F plasmid
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F' plasmid
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F plasmid variant that carries most plasmid genes plus some bacterial genes
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Frameshift mutation
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Insertion or deletion of base pairs that alter the grouping of nucleotides into codons
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Gametes
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Specialized haploid cells that carry genes between generations
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gene
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Basic unit of biological information; specific segment of DNA in a discrete region of a chromosome that serves as a unit of function by encoding a particular RNA or protein
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Genetics
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The science of heredity
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genome
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The sum total genetic information of a cell or organism
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genotype
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The actual alleles present in an individual
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haploid
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a single set of chromosomes present in gametes
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Hemizygous
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Describes the genotype for genes present in only one copy in an otherwise diploid organism, e.g. X-linked genes in males
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Heterozygous
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A genotype in which the two copies of the gene that determine a particular trait are different alleles
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Hfr
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Bacteria that produce a High Frequency of Recombinants for chromosomal genes because their chromosomes contain an integrated F plasmid
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Homologous chromosomes (homologs)
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A pair of chromosomes containing the same linear gene sequence, each derived from one parent
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Homozygous
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A genotype in which the two copies of the gene that determine a particular trait are the same allele
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Incomplete dominance
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Expression of heterozygous phenotype resulting in offspring whose phenotype is intermediate between those of the parents
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Independent assortment
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The random distribution of different genes during gamete formation
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Lateral gene transfer
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The introduction and incorporation of DNA from an unrelated individual or from a different species
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Mendel's First Law - Law of Segregation
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The two alleles for each trait separate during gamete formation and then unite at random, one from each parent, at fertilization
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Mendel's Second Law - Law of Independent Assortment
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During gamete formation, different pairs of alleles segregate independently of each other
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Metaphase
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Stage of meisosis/mitosis when the chromosomes line upalong the equatorial line of the cell
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Missense mutation
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Change in the nucleotide sequence of a gene that change the identity of an amino acid in the polypeptide encoded by that gene
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Mitotic disjunction
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The failure of two sister chromatids to separate during mitotic anaphase generates reciprocal trisomic and monosomic daughter cells
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Monosomic
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Individual lacking chromosome from the diploid number for the species
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Monohybrid cross
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Cross between parents that differ in only one trait
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Monomorphic
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A gene with only one wild-type allele
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Mutagen
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Any physical or chemical agent that raises the frequency of mutations above the spontaneous rate
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Mutation
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Heritable alteration in DNA sequence
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Nondisjunction
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Failure of chromosome segregation during meiosis
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Non-Parental Ditype (NPD)
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A tetrad containing four recombinant spores
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Nonsense mutation
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Mutational change in which a codon for an amino acid is altered to a stop codon
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Null hypothesis
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A statistical hypothesis to be tested and either rejected or accepted in favor of an alternative
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Open Reading Frame (ORF)
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DNA Sequence with long stretches of codons in the same reading frame uninterrupted by stop codons, suggesting the presence og genes
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Operator site
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DNA Sequence near the promoter that can be bound to by a repressor protein
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Operon
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A unit of DNA composed of specific genes, plus a promoter and/or operator, that acts in unison to regulate the response of the structural genes to environmental changes
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Origin of replication
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Sequence of nucleotides at which the initiation of DNA replication begins
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Parental classes
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Combination of alleles present in the original parental generation
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Parental ditype
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A tetrad that contains four parental class haploid cells
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Penetrance
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Indication of how many members of a population with a particular genotype show the expected phenotype
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Phenotype
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An observable characteristic
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Pilus
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Hollow protein tube that protrubes from F+, Hfr or F` bacterial cells and binds to the cell wall of an F- cell; used for gene transfer during conjugation
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Plaque
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A clear area on a bacterial lawn, devoid of living bacterial cells
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Plasmid
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Small circle of doube-stranded DNA that can replicate in bacterial cells independently of the bacterial chromosome
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Polymerase (DNA/RNA)
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Enzymes that catalyze the synthesis of nucleic acids on preexisting nucleic acid templates
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Promoter
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DNA Sequence near the beginning of a gene that signal RNA polymerase where to begin transcription
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Prototroph
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A microorganism that can grow on minimal medium in the absence of one or more growth factors
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recessive allele
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Allele whose phenotype is not expressed in the heterozygote
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Recessive Lethal gene
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An allele that prevents the birth or survival of homozygotes
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Recombinant classes
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Reshuffled combinations of alleles that were not present in the parental generation
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Recombinant
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Chromosome that carries a mix of alleles derived from different homologous chromosomes
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Recombination frequency
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The percentage of recombinant progeny
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Repressor
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A type of transcription factor that can bind to specific cis-acting elements such as operator sites preventing transcription
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RNA Polymerase
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Enzyme that transcribes a DNA sequence into an RNA transcript
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semi-conservative replication
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A pattern of double helix duplication in which complementary base pairing followed by the successive linkage of two nucleotides yields two daughter double helices that each contain one of the original strands intact, and one completely new strand
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Sister chromatids
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The two identical copies of a chromosome that exist immediately after DNA replication
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Substitution
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Occurs when a base at a certain position in one strand of the DNA molecule is replaced by one of the other three bases
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Segregation
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Equal separation of alleles for each trait during gamete formation, in which one allele of each gene goes to each gamete
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Silent mutation
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Mutation with no effect on phenotype
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Temperate bacteriophages
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After infecting the host, these phages can enter either the lyic or kysogenic cycle
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Tetratype
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A fungal ascus carrying four kinds of haploid cells; two different parental classes, and two recombinants
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testcross
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A cross used to determine the genotype of an individual showing a dominant phenotype by mating with an individual showing the recessive phenotype
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tetrad
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The four products of a meiotic division
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Transduction
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Bacterial gene transfer mechanism in which donor DNA is packaged with the protein coat of a bacteriophage and transferred to the recipient when the phage particle infects it
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Translation
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The process in which codons carried by mRNA direct the synthesis of a polypeptide from amino acids according to the genetic code
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Transposable Elements (TEs)
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All DNA segments that move about the genome, regardless of mechanism
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Vector
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A specialized DNA sequence that can enter a living cell, signal its presence to an investigator by conferring a detectable property on the host cell, and provide a means of replication for itself and the foreign DNA inserted into it. A vector must also possess distinguishing traits by which it can be purified away from the host cell's genome
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Virulent bacteriophage
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After infecting the host, these phages always enter the lytic cycle, multiply rapidly, and kill the host.
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Virus
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A noncellular biological entity that can reproduce only within a host cell. Viruses consist of nucleic acid convered by protein
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Wild-type allele
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An allele whose frequency is more than 1% in a population
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Complete Dominance
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A kind of dominance wherein the dominant allele completely masks the effect of the recessive allele in the heterozygote
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Complementation Group
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A collection of mutants that do not complement each other
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Competent
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Cells able to take up DNA from their environment
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Corepressor
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A molecule that binds to transcription factors rather than DNA and prevents transcription above basal levels
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Episome
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Plasmid that can integrate into the host chromosome
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Induction
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Gene activation by a molecule that inactivates a repressor protein, activating transcription of one or more structural genes
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Inducer
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Molecule that acts by binding either to an activator or to a repressor protein to stimulate gene expression.
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Lysogenic cycle
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viral DNA or RNA enters the cell and integrates into the host DNA as a new set of genes
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Lytic cycle
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Bacterial cycle resulting in cell lysis and release of progeny phage
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Point Mutation
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Mutation of one base pair
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Prophage
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Phage genome inserted as part of the DNA of a bacterium
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Reporter Gene
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Protein-encoding gene whose expression in the cell is quantifiable
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Merodiploid
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Partially diploid (having a second copy of only part of its genome)
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