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Recombinant |
Single Crossover |
One point of crossover occurs between the selected point on the parent organism |
NCO |
No Crossover occurs between the selected points on the parent organism strings |
Double Crossover |
Two-point crossover where two points to be selected on the parent organism strings. Everything between the two points is swapped between the parent organisms, rendering two child organisms: |
Coefficient of coincidence |
Ratio of observed double crossovers to expected crossovers |
Interference |
Degree to which one crossover interferes with additional crossovers |
Mapping function |
A function to relate the map distance to the recombination rate. Also takes into consideration that some multiple crossovers will be undetected. Takes into account all crossovers. |
Quantitative trait |
Some measurement such as height, weight, yield (not eye color or ordinal numbers like number of bristles) |
Heritability |
Proportion of phenotypic variation due to genetic differences 0 = no genetic variability 1 = no environmental variablilty |
Broad Sense Heritablity |
Proportion of the phenotyic variance that can be attributed to genetic variance |
Narrow Sense Heritability |
Proportion of the phenotypic variance that can be attributed to additive genetic variance |
Mass selection |
Also truncation selection. A type of selection where we are interested in increasing some quantitative trait through selective breeding |
Selection Differential (SD) |
The selection differential is the difference of the base population mean and the mean of the selected parents. I x Sigma |
Selection Response (SR) |
Difference in mean of original vs mean of offspring H2SD |
Genotypic Array |
Set of genomic frequencies PAA+QAa+Raa |
Gametic Array |
Set of allelic frequencies pA+qa p=P+1/2Q, q=R+1/2Q |
Homozygosity |
Organism that possesses two identical alleles at a locus -In regards to Hardy-Weinberg: Fraction of homozygotes in the population |
Heterozygosity |
Organism that possesses two different alleles at a locus -In regards to Hardy-Weinberg: Fraction of heterozygotes in the population |
Polymorphism |
having multiple alleles of a gene within a population, usually expressing different phenotypes |
Hardy-Weinberg equilibrium |
Important principle of population genetics stating that, in a large, randomly mating population not affected by mutation, migration, or natural selection, allelic frequencies will not change and genotype frequencies stabilize after one generation the proportion is p2, 2pq, q2, where p equals the frequency of allele A and q equals the frequency of allele a. p2AA+2pqAa+p2aa |
Directional Selection |
Selection in which one trait or allele is favored over another. Favored allele is eventually fixed in the population and the other is lost. |
Balancing Selection |
All alleles remain in population but heterozygous fitness is greatest |
Dispersive Selection |
Fitness of heterozygote is smaller than either of the homozygotes |
Overdominance |
Selection in which the heterozygote has higher fitness than than of either homozygote; also called heterozygote advantage |
Underdominance |
Selection in which the heterozygote has lower fitness than that of either homozygote |
Mean Fitness |
The sum of the fitnesses of the genotypes of a population weighted by their proportions; hence a weighted mean fitness. |
Genetic Drift (Random Drift) |
Change in allelic frequency due to sampling error |
Founder Population |
Small population colonizing a new area. -Small size -Not representative of entire population -Undergo Strong Selection |
Ploidy |
is the number of complete sets of chromosomes in a biological cell. |
Euploidy |
True copy number. Refers to mutations that involve excess or deficiency of all all all of the chromosome types |
Aneuploidy |
Derived from a nondisjunction event within a single species. Normally infertile and have an odd number of copies of haploid number |
Nondisjunction |
Failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis |
Autoreplication |
Duplication |
Adding portions of the chromosome |
Deletion |
Mutation in which one or more nucleotides are deleted from a DNA sequence |
Inversion |
When the order of the DNA is rearranged form normal order on the chromosome |
Partial Monosomy |
Monosomy refers to lack of one chromosome of the normal complement. Partial monosomy can occur in unbalanced translocations or deletions, in which only a portion of the chromosome is present in a single copy |
Partial Trisomy |
Trisomy refers to the presence of three copies, instead of the normal two |
Autoploidy |
Derived from a nondisjunction event within single species. Excess or deficiency in single chromosome |
Allopolyploidy |
Having two or more complete sets of chromosomes derived from different species. |
Translocation |
Movement of a chromosome segment to a nonhomologous chromosome or to a region within the same chromosome; also movement of a ribosome along mRNA in the course of translation |
Transposition |
Movement of a transposable genetic element from one site to another. Replicative transposition increases the number of copies of the transposable element; nonreplicative transposition does not increase the number of copies |
Fusion |
Where 2 chromosomes come together |
Fission |
Where 2 Chromosomes split |
Behavior |
Reaction of an organism to environmental stimuli |
Chemotaxis |
is the phenomenon in which bodily cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemicals in their environment. |
Phototaxis |
occurs when a whole organism moves in response to the stimulus light. |
Environmental Bias |
Example: Fish in streams inevitably face upstream |
Concordance |
Percentage of twin pairs in which both twins have a particular trait |
Twin studies |
Allows scientists to study human differences based on environment and genetics when they have itentical (monozygotic twins)genetics or are raised in same environment but have similar genes (monozygotic) |
Single gene behavioral traits |
behavioral traits the are the result of single genes Examples: Lesch-Nyhan Disease, Fragile X, Hygienic Bees |
Threshold trait |
A trait that falls into natural groups that originate not in categorically distinct causes but in whether or not the outcome attains critical values; e.g., gallstones may result from a categorical cause or from unusual levels of causal factors that themselves show no evidence of grouping. |
comparative studies |
studying breeds/species with extreme traits often helps us to understand behavioral traits |
Plasticity |
Selection Intensity |
Variable in Mass selection equations (I) Given for proportion |
Standardized Selection Point |
Value in Mass selection equations (Z) Given for proportion Z=(x-mu)/sigma |
Mean |
Mu |
Standard Deviation |
Sigma |
Proportion selected |
p |
Assortative Mating |
When mates are chosen based on the similarity of their phenotypes. Results in an increase in homozygosity |
Pericentric Inversion |
Includes centrosome |