Ch. 8 Notes Genetics

1. Ch. 8 NotesGenetics By: Brianna Shields November 21, 2005

2. DO NOW • 1. Describe this genotype: BB • 2. What does phenotype describe? • 3. What is the ratio of offspring derived from an F2 generation of pea plants that are descendants of a cross between two pure bred pea plants with opposing traits?

3. Heredity Genetics Monohybrid cross True-breeding P generation F1 generation F2 generation Allele Dominant Recessive Homozygous Heterozygous Genotype Phenotype Law of segregation Law of independent assortment Punnett square Test cross Probability Pedigree Sex-linked trait Polygenic trait Incomplete dominance Multiple alleles Codominance List the terms in your vocab notebook, leaving about 3-4 spaces between each term

4. GOALS • Identify the investigator whose studies formed the basis of modern genetics • List characteristics that make the garden pea a good subject for genetic study • Summarize the three major steps of Gregor Mendel’s garden-pea experiment • Relate the ratios that Mendel observed in his crosses to his data • Describe the major hypotheses Mendel developed • Define the terms homozygous, heterozygous, phenotype and genotype • Compare Mendel’s two laws of heredity • Predict the results of monohybrid genetic crosses by using punnett squares • Apply a test cross to determine the genotype of an organism with a dominant phenotype. • Predict the results of monohybrid genetic crosses by using probabilities • Analyze a simple pedigree • Identify five factors that influence patterns of heredity • Describe how mutations can cause genetic disorders • List the genetic disorders and describe their causes and symptoms • Evaluate the benefits of genetic counseling

5. Heredity The passing of traits from parents to offspring Mendel’s Study of Traits

6. Gregor Mendel Austrian Monk, Father of Genetics Genetics- branch of biology focusing on heredity Crossed pea plants, counted offspring , analyzed data Mendel’s Study of Traits

7. Why are pea plants useful for genetics? 1. Traits exist in 2 opposing forms, without intermediates Mendel’s Study of Traits

8. Why are pea plants useful for genetics? 2. Have male and female organs Easily control mating (self- fertilization or cross-pollination) Stamens removed from one plant, dust pistil with pollen from another plant Mendel’s Study of Traits

9. Why are pea plants useful for genetics? 3. Small, grow easily and quickly, produce many offspring Mendel’s Study of Traits

10. Traits of Pea Plants

11. Monohybrid Cross Involves one pair of contrasting traits Ex: Just flower color Mendel’s Study of Traits

12. True Breeding Allow self-pollination for several generations to ensure offspring displays only one form of trait True breeders serve as parental generation (P) n experiments Mendel’s Study of Traits

13. F1 Generation Offspring from crossing two P generation plants with contrasting forms of a trait Mendel’s Study of Traits

14. F2 Generation Offspring from crossing F1’s who are allowed to self pollinate Mendel’s Study of Traits

16. Mendel’s Results 1. Same 3:1 ratio of plant expressing the contrasting traits in F2 generation Mendel’s Study of Traits

17. Mendel’s Results Example: In each set of data, is the 3:1 ratio found by Mendel verified? Flower Color: 705 purple, 224 white Seed Color: 6022 yellow, 2001 green Seed Shape: 5474 round, 1850 wrinkled Mendel’s Study of Traits

18. Assessment One • Describe the contribution of Mendel to the foundation of modern genetics • Describe why garden pea plants are good subjects for genetic experiments • Summarize the design of Mendel’s pea plant studies • State the ratio Mendel obtained in each F2 generation for each of the traits he studied • What differences would be expected in experiments with squash plants, which usually do not self pollinate?

19. Mendel’s Hypotheses 1. Individuals inherit 2 copies of each gene (trait)- one from each parent 2. Alleles- different contrasting versions of each gene (one from each parent) Mendel’s Study of Traits

20. Mendel’s Hypotheses 3. Dominant- expressed from of a trait 4. Recessive- trait that’s not expressed when the dominant allele is present Mendel’s Study of Traits

21. Mendel’s Hypotheses 5. Gametes carry only one allele for each inherited trait, which they contribute during fertilization Mendel’s Study of Traits

22. Genetics Terms 1. Dominant Traits- Capital letter 2. Recessive Traits- Lowercase letter Mendel’s Study of Traits

23. Genetics Terms 3. Homozygous- two alleles of a present gene are the same (2 dominants or 2 recessives) Mendel’s Study of Traits

24. Genetics Terms 4. Heterozygous- alleles of a gene present are different (one recessive, one dominant) Only the dominant allele is expressed (masks the recessive allele) Ex: Freckles in humans are dominant Mendel’s Study of Traits

26. Genetics Terms 5. Genotype- allele combinations (genes) Ff- Heterozygous FF- Homozygous dominant ff- Homozygous recessive Mendel’s Study of Traits

28. Genetics Terms 6. Phenotype- physical appearance of a trait Ff- freckled Mendel’s Study of Traits

29. Law of segregation 2 alleles for a trait separate when gametes are formed (homologous chromosomes and then chromatids separate in meiosis) Mendel’s Study of Traits

31. Dihybrid crosses Considers two pairs of contrasting traits at once to see if they influence one another Ex: height and color Mendel’s Study of Traits

33. Law of Independent Assortment Inheritance of one trait didn’t effect the inheritance of another Alleles of genes separate independently of one another during gamete formation Only applies to genes on different chromosomes or that are far apart on the same chromosome Mendel’s Study of Traits

35. Assessment Two • Differentiate between alleles and genes. • Apply the terms homozygous, heterozygous, dominant or recessive to describe plants with the genotypes PP and Pp. • Identify the phenotypes of rabbits with the genotypes Bb and bb, where B- black coat and b- brown coat. • Are the above mentioned rabbits heterozygous or homozygous?