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character
A heritable feature that varies among individuals
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Trait
Each variant for a character
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True breeding
Plants that produce offspring of the same variety when they self pollinate
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Hybridization
Corssing of two true-breeding parents
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P generation
True breeding parents
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F1 generation
Hybrid offspring of P generation
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F2 generation
Offspring of F1 generation
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Law of segregation
- 1. Alternative versions of gene account for variations in inherited characters
- 2. For each character; an organism inherits two allels, one from each parent
- 3. If the two allels at a locus differ, then one, the dominate allele, determines the organism's appearance; the other has no noticable affect on the organism's appearance.
- 4. The two allels for a heritable character segregate during gamete formation and end up in different genes.
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allele
Alternative versions of a gene
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Punnett Square
used to predict allel composition of offspring from a cross between individuals of know genetic make up.
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Homozygous
An organism with a pair of identical allels for a character
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Heterozyjous
An organism taht has two different alleles for a gene
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Phenotype
An organism's observed traits
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Genotype
An organism's genetic make up
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Test cross
Breeding an organism of unknown genotype with a recessive homozygote in order to revel the genotype of an organism.
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Monohybrids
Heterogzygous in one character
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Dihybrids
Heterozygous in two characters
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Law of independent assortment
Each pair of alleles segregates independently of each other pair of alleles during gamete formation. *only applies to genes located on different chromosomes*
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Inheritance Deviates from Mendelian Patterns when:
- -alleles are not completely dominate or recessive
- -a gene has more than 2 alleles
- -A single gene produces multiple phenotypes
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Incomplete Dominance
Situation in which the phenotype of herterozygotes is intermediate between the phenotypes of individual's homozyjous of either allele
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Codominance
two alleles both affect the pheontype in separate, distinguishable ways
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Tay-sachs disease
Brain cells cannot metabolize certain lipids and lipids accumulate in the brain.
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Pleiotropy
The ability of a single gene to have multiple effects
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Epistasis
"standing upon", a gene at one locus alters the phenotypic expression of a gene at a second locus
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Quantitative characters
Characters that vary along a continuum. Example-skin pigment varies along a continuum
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Polygenic inheritance
An additive effect of two or more genes on a single phenotypic character
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Norm of reaction
Range of phenotypes produced by a single genotype, due to environment influences. Example-red blood cell count increases at higher elevations
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Multifactorial
Many factors, both genetic and environmental, collectively influence phenotype
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Pedigre
Information about a family's history for a particular trait and assembling this info into a family tree.
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Carrier
Offspring with one recessive allele
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Achondroplasia
A type of dominate trait dwarfism
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Huntington's Disease
Degenerative disease of the nervous system; lethal dominate allele
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Amniocentesis
Needle is inserted into uterus and extracts a 10 mL sample of amniotic fluid
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Chronic villus sampling
Tube is inserted through cervix into uterus and suctions tiny sample of tissue from placenta
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Chromosome Theory of Interitance
Principle stating that genes are located on chromosomes and the behavior of chromosomes during meiosis accounts for inheritance patterns' genes have specific loci along chromosomes and the chromosomes undergo segregation and independent assortment.
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Wild type
Phenotype for a character most commonly observed in natural populations
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Mutant phenotypes
Non wildtypes
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Sex-linked genes
A gene located on either sex chromosome
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Duchenne musculardystrophy
Sex-linked disorder which causes increasing muscle loss caused by a lack of dystrophin
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Hemophilia
Sex-link blood disorder
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Barr body
Inactive X chromosome which condenses and lies along the nuclear envelope of a cell
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Inactivation of X chromosome...
Involves modification of the DNA
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Linked genes
Genes on the same chromosomes that tend to be inherited together in genetic crosses
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Genetic recombination
The production of offspring with combinations of traits that differ from those found in either parent
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Recombinant types
Offspring with new genetic combinations
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Crossing over
Reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis
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Genetic map
an ordered list of the genetic loci along a particular chromosome.
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Probability of crossing over
The farther apart two genes are, the higher the probability that a crossover will occur between them and therefore the higher the recombination frequency.
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Linkage map
A genetic map based on recombination frequencies
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Map units
The distance between genes. One map unit is equivalent to 1% recombination frequency
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Cytogenetic map
locates genes with respect to chromosomal features
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Nondisjunction
Members of a pair of homologous chromosomes do not move apart properly during meiosis I or sister chromatids fail to separate during meiosis II
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Aneuploidy
A chromosomal aberration in which one or more chromosomes are present in extra copies or are deficient in number
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Monosomic
An aneuploid zygote with a missing chromosome
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Trisomic
Three of the same chromosomes are located in a cell
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Polyploidy
Organisms with more than two complete chromosome sets
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Chromosomal deletion
A chromosomal fragment is lost
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Chromosomal duplication
An extra segment on a chromosome
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Chromosomal inversion
A chromosomal fragment attaches in reverse on a chromosome
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Chromosomal Translocation
Chromosome fragment is moved from one chromosome to a nonhomologous chromosome
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Genomic imprinting
Phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent. *caused by methly group that attaches to cytosine nucleotids and silences the allele. Sometimes works in reverse (example: Igf2 allele)
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