The gene is a substance that satisfies two essential requirements:

Gregor Mendel

The term genetics (in Greek, means to generate) was coined by William Bateson in 1905 Original Mendelian definition of the gene (word coined by Johanssen from genetics ):That inherited unit located on chromosomes which determines a biological characteristic A unit of function and mutation The gene is a substance that satisfies two essential requirements: 1) It is inherited between generations in such a way that each descendent has a physical copy of this material 2) It provides information to its carriers in respect to structure, function, and other biological attributes

Mendel s First Law (principle of allelic segregation): Alleles of each gene segregate (separate) at the time of meiosis (gamete formation), so that half the gametes carry one allele and half carry the other

Backcrosses Dd DD D d D DD Dd Dd dd D d d Dd dd Testcrosses DD dd D d Dd P R = 1 Dd dd d d Dd D P R = 1:1 dd To test for genotype (heterozygosity) of a dominant phenotype using a testcross parent (dd) AaBb aabb n=2 2 2 = 4 1:1:1:1 AaBbCc aabbcc n = 3 2 3 = 8 1:1:1:1:1:1:1:1 homologs tetrad

D = Tall (dominant) d = Dwarf (recessive) Include ratios before gametes, phenotypes, and genotypes Circle gametes PR = Phenotypic ratio GR = Genotypic ratio Tall x Tall Tall x Dwarf DD x DD DD x dd Gametes Pheno Geno PR GR Tall x Tall Tall x Dwarf DD x Dd Dd x dd Gametes Pheno Geno PR GR Tall x Tall Dwarf x Dwarf Dd x Dd dd x dd Gametes Pheno Geno PR

D = Tall (dominant) d = Dwarf (recessive) Include ratios before gametes, phenotypes, and genotypes Circle gametes PR = Phenotypic ratio GR = Genotypic ratio Tall x Tall Tall x Dwarf DD x DD DD x dd Gametes 1/1 D x 1/1 D 1/1 D x 1/1 d Pheno _1/1 Tall 1/1 Tall Geno _1/1 DD 1/1 Dd PR 1 1 GR 1 1 Tall x Tall Tall x Dwarf DD x Dd Dd x dd Gametes 1/1 D x 1/2 D 1/2 d 1/2 D 1/2 d x 1/1 d Pheno 1/1 Tall 1/2 Tall 1/2 Dwarf Geno 1/2 DD 1/2 Dd 1/2 Dd 1/2 dd PR 1 1:1 GR 1:1 1:1 Tall x Tall Dwarf x Dwarf Dd x Dd dd x dd Gametes 1/2 D 1/2 d x 1/2 D 1/2 d 1/1 d x 1/1 d Pheno 3/4 Tall ¼ Dwarf 1/1 Dwarf Geno 1/4 DD 2/4Dd 1/4dd 1/1 dd PR 3:1 1 GR 1:2:1 1

Using the information given, fill in all blanks below Circle each gamete Autosomal trait in Drosophila melanogaster V = Normal wings (dominant); v = Vestigial wings (recessive) P Phenotypes Normal x Vestigial Genotypes VV x vv Gametes x F 1 Phenotypes x Genotypes x Gametes x F 2 Phenotypes Genotypes F 2 Phenotypic ratio F 2 Genotypic ratio Use the information above to make a testcross below F 1 Parent x Testcross parent Phenotypes x Genotypes x Gametes x Testcross Phenotypes Genotypes Testcross phenotypic ratio Testcross genotypic ratio

Using the information given, fill in all blanks below Circle each gamete Autosomal trait in Drosophila melanogaster V = Normal wings (dominant); v = Vestigial wings (recessive) P Phenotypes Normal x Vestigial Genotypes VV x vv Gametes 1/1 V x 1/1 v F 1 Phenotypes Normal x Normal Genotypes Vv x V v Gametes 1/2 V 1/2 v x 1/2 V 1/2 v F 2 Phenotypes 3 Normal 1 Vestigial Genotypes 1 VV 2 Vv 1 vv F 2 Phenotypic ratio 3:1 F 2 Genotypic ratio 1:2:1 Use the information above to make a testcross below F 1 Parent x Testcross parent Phenotypes Normal x Vestigial Genotypes Vv x vv Gametes 1/2 V 1/2 v x 1/1 v Testcross Phenotypes Normal Vestigial Testcross phenotypic ratio 1:1 Testcross genotypic ratio 1:1 Genotypes Vv vv

Using the information given, fill in all blanks below Circle each gamete Autosomal trait in Pisum sativum T = Axial pods (dominant); t = Terminal pods (recessive) P Phenotypes Axial x Terminal Genotypes TT x tt Gametes x F 1 Phenotypes x Genotypes x Gametes x F 2 Phenotypes Genotypes F 2 Phenotypic ratio F 2 Genotypic ratio Use the information above to make a testcross below Testcross F 1 Parent x Testcross parent Phenotypes x Genotypes x Gametes x Testcross Phenotypes Genotypes Testcross phenotypic ratio Testcross genotypic ratio

Using the information given, fill in all blanks below Circle each gamete Autosomal trait in Pisum sativum T = Axial pods (dominant); t = Terminal pods (recessive) P Phenotypes Axial x Terminal Genotypes TT x tt Gametes 1/1 T x 1/1 t F 1 Phenotypes Axial x Axial Genotypes Tt x Tt Gametes 1/2 T 1/2 t x 1/2 T 1/2 t F 2 Phenotypes 3/4 Axial 1/4 Terminal Genotypes 1/4 TT 2/4 Tt 1/4 tt F 2 Phenotypic ratio 3:1 F 2 Genotypic ratio 1:2:1 Use the information above to make a testcross below Testcross F 1 Parent x Testcross parent Phenotypes Axial x Terminal Genotypes Tt x tt Gametes 1/2 T 1/2 t x 1/1 t Testcross Phenotypes Genotypes 1/2 Axial 1/2 Tt 1/2 Terminal 1/2 tt Testcross phenotypic ratio 1:1 Testcross genotypic ratio 1:1

Include ratios before gametes, phenotypes, and genotypes Circle gametes RR = Red, RR' = Roan, R'R' = White (Example of codominance; however, ratios similar to semidominance in crosses) Red X Red Red X Roan Geno X X Gametes X X Pheno Geno PR GR Red X White Roan X Roan Geno X X Gametes X X Pheno Geno PR GR Roan X White White X White Geno X X Gametes X X Pheno Geno PR GR

RR = Red, RR' = Roan, R'R' = White Red X Red Red X Roan Geno RR X RR RR X RR Gametes 1/1 R X 1/1 R 1/1 R X 1/2 R 1/2 R Pheno 1/1 Red 1/2 Red 1/2 Roan Geno 1/1 RR 1/2 RR 1/2 RR PR 1 1:1 GR 1 1:1 Red X White Roan X Roan Geno RR X R R RR X RR Gametes 1/1 R X 1/1 R 1/2 R 1/2 R X 1/2 R 1/2 R Pheno 1/1 Roan 1/4 Red 2/4 Roan 1/4 White Geno 1/1 RR 1/4 RR 2/4 RR 1/4 R R PR 1 1:2:1 GR 1 1:2:1 Roan X White White X White Geno RR X R R R R X R R Gametes 1/2 R 1/2 R X 1/1 R 1/1 R X 1/1 R Pheno 1/2 Roan 1/2 White 1/1 White Geno 1/2 RR 1/2 R R 1/1 R R PR 1:1 1 GR 1:1 1

Using the information given, fill in all blanks below Circle each gamete Illustrate crosses and results for semidominant inheritance of an autosomal trait in cattle RR = Red; RR = Roan; R R = White P Phenotypes X Genotypes RR X R R Gametes X F Phenotypes X 1 Genotypes X Gametes X Phenotypes F 2 Genotypes Phenotypic ratio F 2 F 2 Genotypic ratio Use the information above to make a testcross below: F 1 Parent X Testcross Parent Phenotypes X Genotypes X Gametes X Testcross Phenotypes Genotypes Testcross phenotypic ratio Testcross genotypic ratio

Using the information given, fill in all blanks below Circle each gamete Illustrate crosses and results for semidominant inheritance of an autosomal trait in cattle RR = Red; RR = Roan; R R = White P Phenotypes Red X White Genotypes RR X R R Gametes 1/1 R X 1/1 R F 1 Phenotypes Roan X Roan Genotypes RR X RR Gametes 1/2 R 1/2 R X 1/2 R 1/2 R F 2 Phenotypes 1/4 Red 2/4 Roan 1/4 White Genotypes 1/4 RR 2/4 RR 1/4 R R F 2 Phenotypic ratio 1:2:1 F 2 Genotypic ratio 1:2:1 Testcross Cannot make a testcross because you do not have an organism that is homozygous recessive for all genes in question

A Horse with the BASE color of: A Red based horse with no black gene and no dilution gene With ONE crème dilution gene added becomes: A sorrel/chestnut horse that received one copy of the crème dilution gene from one of its parents, giving it a coat ranging in color from pale cream, to golden, to chocolate and has a white mane and tail With TWO crème dilution genes added becomes: A sorrel/chestnut horse that received one copy of the crème gene from both of its parents, and has pink skin, blue eyes, cream to nearly white hair coat, and a white mane and tail

A Horse with the BASE color of: A Black based horse with the "bay" gene, which restricts the black to the mane, tail and legs (also called black "points") and no dilution gene With ONE crème dilution gene added becomes: A Bay horse that received one copy of the crème dilution gene from one of its parents, giving it a diluted hair coat (the color can range from very pale cream, to gold, to a dark "smutty" color,) and has black "points" With TWO crème dilution genes added becomes: A Bay horse that received one copy of the crème gene from both of its parents, and has pink skin, blue eyes, a cream to white colored coat and a darker mane and tail (often orange or red tinted)

A Horse with the BASE color of: A Black based horse with no "bay" gene, and no dilution gene, ranging from "true" black to brown in appearance With ONE crème dilution gene added becomes: A Black horse that received one copy of the crème dilution gene from one of its parents, but probably looks no different than any other black or brown horse With TWO crème dilution genes added becomes: A Black horse that received one copy of the crème gene from both of its parents, possessing pink skin, blue eyes, and an orange or red cast to the entire hair coat

Colors Mixed Cremello Perlino Smoky Cream Palomino Buckskin Smoky Black Sorrel 100% Palomino Bay 100% Buckskin 50% Palomino 50% Sorrel 50% Buckskin, 50% Bay Black 100% Smoky black 50% Smoky black, 50% Black Palomino 50% Palomino 50% Cremello 50% Palomino, 25% Sorrel, 25% Cremello Buckskin 50% Buckskin, 50% Perlino 50% Buckskin, 25% Bay, 25% Perlino

Colors Mixed Smoky Black Cremello Perlino Smoky Cream 50% Smoky black, 50% Smoky Cream Palomino Buckskin Smoky Black 50% Smoky black, 25% Black, 25% Smoky cream Cremello 100% Cremello 50% Cremello, 50% Palomino Perlino 100% Perlino 50% Perlino, 50% Buckskin Smoky Cream 100% Smoky Cream 50% Smoky Cream, 50% Smoky Black