What is a Trait? What is Genetics? What are Genes? What is an Allele? Mendel s Conclusions. Gregor Mendel 1/11/2016

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1 Wha is Geneics? Geneics is he scienific sudy of herediy Wha is a rai? A rai is a specific characerisic ha varies from one individual o anoher. Examples: Brown hair, blue eyes, all, curly Wha is an Allele? Wha are Genes? Alleles are he differen possibiliies for a given rai. Every rai has a leas wo alleles (one from he moher and one from he faher) Example: Eye color Brown, blue, green, hazel Examples of Alleles: A = Brown Eyes a = Blue Eyes B = Green Eyes b = Hazel Eyes Genes are he sequence of DNA ha codes for a proein and hus deermines a rai. Gregor Mendel Faher of Geneics 1 s imporan sudies of herediy Idenified specific rais in he garden pea and sudied hem from one generaion o anoher Mendel s Conclusions 1.Law of Segregaion wo alleles for each rai separae when gamees form; Parens pass only one allele for each rai o each offspring 2.Law of Independen Assormen Genes for differen rais are inheried independenly of each oher 1

2 Dominan vs. Recessive Dominan - Masks he oher rai; he rai ha shows if presen Represened by a capial leer R Recessive An organism wih a recessive allele for a paricular rai will only exhibi ha rai when he dominan allele is no presen; Will only show if boh alleles are presen Represened by a lower case leer r Dominan & Recessive Pracice sraigh hair - curly hair - Represen offspring wih sraigh hair - Represen offspring wih sraigh hair - Represens offspring wih curly hair Genoype vs. Phenoype Genoype he geneic makeup of an organism; he gene (or allele) combinaion an organism has. Example:, ss, GG, Ww Phenoype he physical characerisics of an organism; he way an organism looks Example: Curly hair, sraigh hair, blue eyes, all, green Homozygous vs. Heerozygous Homozygous erm used o refer o an organism ha has wo idenical alleles for a paricular rai ( or ) Heerozygous - erm used o refer o an organism ha has wo differen alleles for he same rai () RR rr Rr Punne Squares Punne Square Punne Square Diagram showing he gene combinaions ha migh resul from a geneic cross Used o calculae he probabiliy of inheriing a paricular rai Probabiliy he chance ha a given even will occur Paren Paren Offspring 2

3 How o Complee a Punne Square Y-Yellow y-whie Genoype: 1:2:1 (YY:Yy:yy) Phenoype: 3 Yellow 1 Whie You ry I Now! Give he genoype and phenoype for he following cross: x ( = all and = Shor) x Sep One: Se Up Punne Square (pu one paren on he op and he oher along he side) x Sep wo: Complee he Punne Square x Sep hree: Wrie he genoype and phenoype Genoype: 4 - Phenoype: 100% all Remember: Each box is 25% 3

4 You ry I Now! Give he genoype and phenoype for he following cross: x x Sep One: Se Up Punne Square (pu one paren on he op and he oher along he side) x Sep wo: Complee he Punne Square x Sep wo: Complee he Punne Square Genoype: - 2 (50%) - 2 (50%) Remember: Each box is 25% Phenoype: 50% all 50% Shor Mach he vocabulary word wih he correc 1. Genoype A. he differen possibiliies for a given rai. definiion 2. Phenoype B. erm used o refer o an organism ha has wo idenical alleles for a paricular rai 3. Heerozygous C. he physical characerisics of an organism 4. Homozygous D. he gene (or allele) combinaion an organism has 5. Allele E. erm used o refer o an organism ha has wo differen alleles for he same rai Some erminology P 1 Original parens F 1 Firs generaion F 2 Second generaion Wha is he genoype and phenoypes for he following crosses: 6. Hh x HH, where H= Yellow hair, and h= Orange hair 7. ss x ss, where S= freckles, and s= no freckles. P 1 X P 1 = F 1 F 1 X F 1 = F 2 4

5 Incomplee Dominance Incomplee Dominance - Siuaion in which one allele is no compleely dominan over anoher. Example Red and whie flowers are crossed and pink flowers are produced. Codominance Codominance - Siuaion in which boh alleles of a gene conribue o he phenoype of he organism. Example A solid whie cow is crossed wih a solid brown cow and he resuling offspring are spoed brown and whie (called roan). + Muliple Alleles Muliple Alleles- hree or more alleles of he same gene. Even hough hree or more alleles exis for a paricular rai, an individual can only have wo alleles - one from he moher and one from he faher. Examples of Muliple Alleles 1. Coa color in rabbis is deermined by a single gene ha has a leas four differen alleles. Differen combinaions of alleles resul in he four colors you see here. Examples of Muliple Alleles 2. Blood ype 3 alleles exis (I A, I B, and i), which resuls in four differen possible blood ypes 3. Hair Color oo many alleles exis o coun here are over 20 differen shades of hair color. Muliple Alleles here Are Always Muliple Alleles! Geneic inheriance is ofen presened wih sraighforward examples involving only wo alleles wih clear-cu dominance. his makes inheriance paerns easy o see. Bu very few rais acually only have wo alleles wih clear-cu dominance. As we learn more abou geneics, we have found ha here are ofen hundreds of alleles for any paricular gene. We probably know his already - as we look around a oher people, we see infinie variaion. 5

6 Polygenic rai Polygenic rai - rai conrolled by wo or more genes. Polygenic rais ofen show a wide range of phenoypes. Example: he wide range of skin color in humans comes abou parly because more han four differen genes probably conrol his rai. 6