100%(2)2 out of 2 people found this document helpful
This preview shows page 1 - 3 out of 33 pages.
Dr. Uniacke’s Lecture Material Gene: a genetic factor (region of DNA) that helps determine characteristicAllele: one of two or more alternative forms of a gene Locus: specific place on a chromosome occupied by an allele Recessive MutationsNull/amrophic alleles: non-functional and no protein is producedHypomorphic alleles: poorly functioning and reduces amount of protein produced Dominant MutationsHypermorphic: Over production of normal protein OR increased activity levels Neomorphic: presence of altered protein has a new functionAutosomal dominant traits are most likely to be heterozygous (Bb)Incompletedominance: BB, Bb, and bb all differ phenotypically (flower colour, red, white, pink)CodominanceBB, Bb, and bb all differ phenotypically but Bb exhibits phenotypes of both BB and bb (blood type)Allelic series/dominance series: when some genes have many allelesHaplosufficency: half as much protein is synthesized, yet this is enough to achieve wildtype phenotype e.g Huntington’s Disease Haploinsufficency: half as much protein is synthesized, this is not enough to achieve wildtype phenotype e.g tailless cats (Manx) needs two copies of allele to get tail Penetrance: proportion of individual organisms having a particular genotype; variation in the population Complete: identical known genotypes yield 100% expected phenotypeIncomplete: identical known genotypes yield <100% (e.g polydactyl = extra digits) Variance: degree to which a phenotype is expressed; variation in individual Constant: identical known genotypes with no expressivity effect yield 100% expected phenotype Variable: expressivity effect yield range of phenotypesIncomplete: produce broad range of phenotypes, due to varying degrees of gene activation (e.g Huntington’s disease)Phenocopy: change in phenotype arising from environmental factors that mimic the effects of a mutation in a gene Complementation(9:7): when two strains of an organism with different homozygous recessive mutations that reproduce the sae phenotype, produce offspring of the wild-type phenotype White x White Black C/c A/ac/c A/A C/C a/a Genetic Epistasis
Masking of the expression of one gene by anotherRecessive- 9:3:4; homozygous recessive at one gene pair mask expression from other geneA/- b/b and a/a b/b have the same phenotypeDominant- 12:3:1; one dominant allele at one gene mask the expression from the other geneA/- B/- and A/- b/b have the same phenotype Summary of F2 RatiosMonohybrid3:1Complete dominance1:2:1 Incomplete dominance2:1recessive lethalDihybrid9:3:3:1Complete dominance9:3:4Recessive epistasis12:3:1Dominant epistasis 9:7ComplementationPleiotropy: single gene responsible for number of distinct phenotypic effectsEg. Sickle cell disease, cystic fibrosisInbreeding depression: inbred lines of plants are often less vigorous than hybrid linesHeterosis: when two different inbred lines are crosses, the hybrids are heterozygous for many genes and display hybrid vigour Inbreeding increases frequency of homozygous and decreases heterozygous Polyploidy