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31 Cards in this Set
- Front
- Back
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Genetics
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analysis of inheritance patterns to identify and characterize genes
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Genes
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biological factors that induce particular traits
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Alleles
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alternate forms of a given gene, inherited from different parents
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Locus
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location on a chromosome, often used to refer to the gene at that site
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Dominant
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an allele which always determines the phenotype
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Recessive
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allele which only determines phenotype in the absence of a dominant allele
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Mutant
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an entity that carries a mutation. The entity can be an allele, or an individual.
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Wild Type
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an allele, or individual, that is not mutated; occurring normally in nature. Wild type alleles are usually dominant.
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Genotype
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the combination of alleles in an individual
e.g. the genotype for someone with a Brown eye allele and blue eye allele is Bb |
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Phenotype
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observable characteristics. The physical manifestation of the genotype.
e.g. the phenotype of a Bb person is brown eyes. |
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Homozygous
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to carry both copies of the same allele, i.e. both dominant or recessive (BB or bb)
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Heterozygous
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to have different alleles, i.e. one dominant one recessive (Bb)
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Monohybrid Cross
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a cross where one gene locus is tracked, e.g. Aa x Aa
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Dihybrid Cross
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a cross where two loci are tracked, e.g. AaBb x AaBb
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Independent Assortment
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inheritance of alleles at one locus does not influence inheritance at other loci
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sex chromosome
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sex determining chromosome, X or Y
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autosome
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any chromosome except X or Y
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autosomal
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any gene not located on X, or characteristic not associated with X
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complementaion tests
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ask if two mutants with the same phenotype are produced by mutations of the same gene, or by mutations of separate genes. For instance, thalissemia can be produced by mutations of either α or β hemoglobins.
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Nonmendelian Genetics
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genetic interactions other than the autosomal recessive pattern characterized by Mendel. Inheritance patterns include semidominance, codominance, polygenic inheritance, epistasis, X linkage, sex influenced inheritance, and linkage.
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Semidominance
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partial or incomplete dominance- Different alleles for a particular gene have equal effects, so that heterozygotes have intermediate phenotypes, e.g pink flowers
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T/F: Semidominant phenotypic ratios are the same as genotypic ratios.
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True
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Codominance
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Different alleles for a gene that impart independent effects on phenotype. e.g. A & B bloodtypes;
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Epistasis
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For a gene to mask the phenotype of another gene, at another locus. This is not a dominant allele masking a recessive allele; this is a gene suppressing the phenotype of a totally different gene.
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In epistasis, the gene that masks the phenotype is called a ______. It is also said to be ______ to the gene it suppresses.
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suppressor, epistatic; the suppressed gene is sometimes described as hypostatic. Note, a procedure known as an epistasis analysis is used to order genes in regulatory pathways.
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Characteristics of X Linkage
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X linked recessive alleles are passed from affected grandfathers, through unaffected mothers, to affected grandsons. Thus they are expressed in males more often than females.
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Dosage Compensation
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mechanism to adjust expression of X linked genes; genetic imbalance exists because females have two X chromosomes & possess twice as many X linked genes as males
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X Inactivation
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(dosage compensation)-inactivatation of one X chromosome in each blastomere. These
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Barr Bodies
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Condensed (heterochromatic in X chromosomes from X inactivation.
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genetic mosaics
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female mammals; body regions where all cells have the same inactivated X chromosome. e.g. calico cats.
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X chromosome inactivation occurs early in embryogenesis, around the ___ cell stage.
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64
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