1. Monohybrid Notes

2. Gregor Mendel Mendel was an Austrian monk. Mendel formulated two fundamental laws of heredity in the early 1860's. He had studied science and mathematics (including statistics) at the University of Vienna. Mendel’s knowledge of statistics later proved valuable in his research on Heredity – the transmission of characteristics from Parent to Offspring. Mendel's work was unrecognized until 1900.

3. Law of Segregation: Each organism contains two factors for each trait; factors segregate in the formation of gametes. When two gametes combine during fertilization, the offspring have two factors controlling a specific trait. Law of Independent Assortment: states that factors for different characteristics are distributed to gametes independently.

7. Genetics Vocabulary Gene - the unit of heredity; a section of DNA sequence encoding a single protein Alleles - two genes that occupy the same position on homologous chromosomes and cover the same trait Locus - a fixed location on a strand of DNA where a gene or one of its alleles is located

8. Genetics Vocabulary Homozygous - having identical genes (one from each parent) for a particular characteristic. Heterozygous - having two different genes for a particular characteristic.

9. Genetics Vocabulary Phenotype - appearance (description) Genotype - genetic makeup (letter code)

10. Genetics Vocabulary Dominant - the trait that appears in the heterozygous condition. Recessive - the trait that is masked in the heterozygous condition.

11. Genetics Vocabulary Incomplete Dominance - a form of intermediate inheritance in which one allele for a specific trait is not completely dominant over the other. If the trait is incomplete it will be stated in the problem.

12. Genetics Vocabulary Codominance - A condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other. If the trait is codominant it will be stated in the problem. RR RW WW

13. Genetics Vocabulary Monohybrid cross - cross involving a single pair of genes, one trait P – “parents” F1 – “kids” F2 – “grandkids”

14. Genetics Vocabulary Punnett squares - used to aid in predicting the probability that certain traits will be inherited by offspring Probability - is the likelihood that a specific event will occur or is the likely outcome a given event will occur from random chance

15. 1. Determine the dominant and recessive trait Will be stated in the problem ie. Black is dominant to white in bunnies Monohybrid Crosses

16. 2. Assign letters for the trait Dominant trait gets the capital letter Recessive traits gets the lower case letter B = black b = white

17. 3. Determine genotype for parents White male = bb Heterozygous black female = Bb

18. 4. Put parents on the square Bb x bb B b b

19. 5. Determine genotype of offspring Punnett square holds offspring genotypes B b b Genotype = letter code Bbbb Bbbb

20. 6. Determine genotype ratio Count offspring in the Punnett square genotype ratio = 2Bb:2bb

21. 7. Determine phenotype ratio Phenotype = what they look like Count offspring in the Punnett square phenotype ratio = 2 black:2 white *If ratio doesn’t add up to total number of boxes in the punnett square you’ve made a mistake

22. Practice Problems A pure-breed white flower crosses with a pure-breed purple flower. Purple is dominant to white. Show the punnett square What is the genotype of the F1 generation What is the phenotype of the F1 generation

23. Genotype = Pp Phenotype = Purple

24. More practice A homozygous black rat is crossed with a heterozygous black rat. B = blackb = brown Show the punnett square What are the genotypes of F1? What are the genotype ratio of F1?

25. Genotypes = BB and Bb Genotype Ratio = 2BB:2Bb

26. More practice If you had a black rat how could you tell it’s genotype was homozygous or heterozygous?

27. Use a test cross: cross with a pure breed recessive and look at the F1 generation

28. Possible Answer Formats % - chance out of total possible –1 out of 4 = 25% Fraction –1 out of 4 = 1/4 Ratio – ratio adds up to total possible –1 out of 4 = 1:3