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NCSU Genetics 311 Emigh Exam 2
Exam 2
61
Science
Undergraduate 3
04/29/2009

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Term
Recombinant
Definition
Term
Single Crossover
Definition
One point of crossover occurs between the selected point on the parent organism
Term
NCO
Definition
No Crossover occurs between the selected points on the parent organism strings
Term
Double Crossover
Definition
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:
Term
Coefficient of coincidence
Definition
Ratio of observed double crossovers to expected crossovers
Term
Interference
Definition
Degree to which one crossover interferes with additional crossovers
Term
Mapping function
Definition
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.
Term
Quantitative trait
Definition
Some measurement such as height, weight, yield (not eye color or ordinal numbers like number of bristles)
Term
Heritability
Definition
Proportion of phenotypic variation due to genetic differences
0 = no genetic variability
1 = no environmental variablilty
Term
Broad Sense Heritablity
Definition
Proportion of the phenotyic variance that can be attributed to genetic variance
Term
Narrow Sense Heritability
Definition
Proportion of the phenotypic variance that can be attributed to additive genetic variance
Term
Mass selection
Definition
Also truncation selection. A type of selection where we are interested in increasing some quantitative trait through selective breeding
Term
Selection Differential (SD)
Definition
The selection differential is the difference of the base population mean and the mean of the selected parents.
I x Sigma
Term
Selection Response (SR)
Definition
Difference in mean of original vs mean of offspring
H2SD
Term
Genotypic Array
Definition
Set of genomic frequencies
PAA+QAa+Raa
Term
Gametic Array
Definition
Set of allelic frequencies
pA+qa
p=P+1/2Q, q=R+1/2Q
Term
Homozygosity
Definition
Organism that possesses two identical alleles at a locus
-In regards to Hardy-Weinberg: Fraction of homozygotes in the population
Term
Heterozygosity
Definition
Organism that possesses two different alleles at a locus
-In regards to Hardy-Weinberg: Fraction of heterozygotes in the population
Term
Polymorphism
Definition
having multiple alleles of a gene within a population, usually expressing different phenotypes
Term
Hardy-Weinberg equilibrium
Definition
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
Term
Directional Selection
Definition
Selection in which one trait or allele is favored over another. Favored allele is eventually fixed in the population and the other is lost.
Term
Balancing Selection
Definition
All alleles remain in population but heterozygous fitness is greatest
Term
Dispersive Selection
Definition
Fitness of heterozygote is smaller than either of the homozygotes
Term
Overdominance
Definition
Selection in which the heterozygote has higher fitness than than of either homozygote; also called heterozygote advantage
Term
Underdominance
Definition
Selection in which the heterozygote has lower fitness than that of either homozygote
Term
Mean Fitness
Definition
The sum of the fitnesses of the genotypes of a population weighted by their proportions; hence a weighted mean fitness.
Term
Genetic Drift (Random Drift)
Definition
Change in allelic frequency due to sampling error
Term
Founder Population
Definition
Small population colonizing a new area.
-Small size
-Not representative of entire population
-Undergo Strong Selection
Term
Ploidy
Definition
is the number of complete sets of chromosomes in a biological cell.
Term
Euploidy
Definition
True copy number. Refers to mutations that involve excess or deficiency of all all all of the chromosome types
Term
Aneuploidy
Definition
Derived from a nondisjunction event within a single species. Normally infertile and have an odd number of copies of haploid number
Term
Nondisjunction
Definition
Failure of homologous chromosomes or sister chromatids to separate in meiosis or mitosis
Term
Autoreplication
Definition
Term
Duplication
Definition
Adding portions of the chromosome
Term
Deletion
Definition
Mutation in which one or more nucleotides are deleted from a DNA sequence
Term
Inversion
Definition
When the order of the DNA is rearranged form normal order on the chromosome
Term
Partial Monosomy
Definition
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
Term
Partial Trisomy
Definition
Trisomy refers to the presence of three copies, instead of the normal two
Term
Autoploidy
Definition
Derived from a nondisjunction event within single species. Excess or deficiency in single chromosome
Term
Allopolyploidy
Definition
Having two or more complete sets of chromosomes derived from different species.
Term
Translocation
Definition
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
Term
Transposition
Definition
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
Term
Fusion
Definition
Where 2 chromosomes come together
Term
Fission
Definition
Where 2 Chromosomes split
Term
Behavior
Definition
Reaction of an organism to environmental stimuli
Term
Chemotaxis
Definition
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.
Term
Phototaxis
Definition
occurs when a whole organism moves in response to the stimulus light.
Term
Environmental Bias
Definition
Example: Fish in streams inevitably face upstream
Term
Concordance
Definition
Percentage of twin pairs in which both twins have a particular trait
Term
Twin studies
Definition
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)
Term
Single gene behavioral traits
Definition
behavioral traits the are the result of single genes
Examples: Lesch-Nyhan Disease, Fragile X, Hygienic Bees
Term
Threshold trait
Definition
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.
Term
comparative studies
Definition
studying breeds/species with extreme traits often helps us to understand behavioral traits
Term
Plasticity
Definition
Term
Selection Intensity
Definition
Variable in Mass selection equations (I)
Given for proportion
Term
Standardized Selection Point
Definition
Value in Mass selection equations (Z)
Given for proportion
Z=(x-mu)/sigma
Term
Mean
Definition
Mu
Term
Standard Deviation
Definition
Sigma
Term
Proportion selected
Definition
p
Term
Assortative Mating
Definition
When mates are chosen based on the similarity of their phenotypes. Results in an increase in homozygosity
Term
Pericentric Inversion
Definition
Includes centrosome
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