Inheritance

Name: __________________ Topic: Inheritance LO:Definea geneasa unitofinheritanceanddistinguishclearlybetweentheterms gene and allele ●A gene is aunit of inheritance.●Alleles aredifferent forms of the same gene.●Allelesoccupythe samerelativepositions/genelocion a pairof homologouschromosomes. LO: Explainthe termsdominant,recessive,codominant,homozygous,heterozygous, phenotype and genotype ●Dominantallelereferstoanallelethatexpressesitselfandgivesthesamephenotypeinboth homozygous and heterozygous conditions. ●Recessiveallelereferstoanallelethatonlyexpressesitselfinthephenotypeinthehomozygous condition. ●Codominanceis a conditionwherebothallelesexpressthemselvesequallyin thephenotype. Eg; I A and I B alleles in blood group ●Homozygousreferstoanorganismthathasidenticalallelesforaparticularphenotype/ trait. Concepts Summary NotesNan Hua High School Biology 1

Name: __________________ Topic: Inheritance ●Heterozygousrefersto an organismthathasdifferentallelesfor a particularphenotype / trait. ●Phenotypeistheexpressedtraitinanorganism. Eg;observablefeaturessuchaseyecolour and height. ●Genotype is thegenetic make-up of an organism. LO:Predicttheresultsofsimplecrosseswithexpectedratiosof3:1and1:1,using the terms homozygous, heterozygous, F1 generation and F2 generation ●To obtainanexpectedratioof3:1intheoffspringgeneration,bothparentsmustbeheterozygousfor a trait. Genetic diagram: Parent Male x FemalePhenotype Tall x TallGenotype Tt x Tt Gametes F1 genotype TT Tt Tt ttF1 phenotype tall tall tall shortPhenotypic ratio 3 tall: 1 short Concepts Summary NotesNan Hua High School Biology 2

Name: __________________ Topic: Inheritance ●To obtainanexpectedratioof 1:1in theoffspringgeneration,oneparentmustbeheterozygouswhilethe other is homozygous recessive. (test cross) Genetic diagram: Parent Male x FemalePhenotype Tall x shortGenotype Tt x tt Gametes F1 genotype Tt Tt tt ttF1 phenotype tall tallshort shortPhenotypic ratio 2 tall: 2 short= 1 tall: 1 short Note:Todetermineifthegenotypeishomozygousdominantorheterozygousdominant,atestcrosswithahomozygousrecessivecanbeused.Ifitishomozygousdominant,alltheoffspringwillshowthetrait.Ifitisheterozygousdominant,theratioofdominanttraitto recessive trait will be 1