Genetics

1. Genetics Why do we look the way we do?

2. Genetics&The Work of Mendel

3. Gregor Mendel • Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas • used good experimental design • usedmathematicalanalysis • collected data & counted them • excellent example of scientific method

4. Mendel’s work Pollen transferred from white flower to stigma of purple flower • Bred pea plants • cross-pollinate true breeding parents • planted seeds & then observed traits • allowed offspring to self-pollinate& observed next generation all purple flowers result self-pollinate ?

5. Mendel collected data for 7 pea traits

6. true-breeding purple-flower peas true-breeding white-flower peas 100% purple-flower peas 1st generation (hybrids) 100% 75% purple-flower peas 25% white-flower peas 3:1 2nd generation Looking closer at Mendel’s work X Parents self-pollinate

7. true-breeding purple-flower peas true-breeding white-flower peas 100% purple-flower peas 1st generation (hybrids) 100% 75% purple-flower peas 25% white-flower peas 3:1 2nd generation Looking closer at Mendel’s work X Parents self-pollinate

8. What did Mendel’s findings mean? • Some traits mask others • purple & white flower colors are separate traits that do not blend • purple x white ≠ light purple • purplemaskedwhite • dominant allele • functional protein • affects characteristic • masks other alleles • recessive allele • no noticeable effect • allele makes a non-functioning protein I’ll speak for both of us! allele producingfunctional protein allele producingnonfunctioningprotein homologouschromosomes

9. X P purple white F1 all purple Genotype vs. phenotype • Difference between how an organism “looks” & its genetics • phenotype • description of an organism’s trait • genotype • description of an organism’s genetic makeup Explain Mendel’s results using …dominant&recessive …phenotype&genotype

10. PP pp x X P purple white F1 all purple Making crosses • Can represent alleles as letters • flower color alleles  P or p • true-breeding purple-flower peas  PP (homozygous dominant) “same zygote” • true-breeding white-flower peas  pp (homozygous recessive) • hybrid purple flower peas Pp (heterozygous) “different zygote” Pp

11. R – dominant allele (tongue roller) Is Rr homozygous or heterozygous? Heterozygous B – dominant allele (baldness) Is bb homozygous or heterozygous? Homozygous F – dominant allele (freckles) Is FF homozygous or heterozygous? Homozygous

12. PP 25% male / sperm P p Pp 50% 75% P Pp female / eggs pp p 25% 25% Punnett squares Aaaaah, phenotype & genotypecan have different ratios 1st generation (hybrids) Pp x Pp % genotype % phenotype PP Pp Pp pp 1:2:1 3:1

13. Write a two sentence summary comparing phenotype & genotype As well as heterozygous & homozygous