1. 7.1 MENDEL & ONE TRAIT CROSSES

2. Lesson Objectives  Students will be able to:  Explain the major experiments conducted by Gregor Mendel  Define genes, alleles, genotype, phenotype  Demonstrate mastery of one-trait crosses by using punnett squares to complete genetics problems

3. History: Gregor Mendel  1822-1884  Austrian monk that studied pea plants  Papers were rediscovered in 1900  Called Father of Genetics

4. Genes & Alleles  Genes:  Sequence of nucleotides on chromosome  Codes for a protein  Alleles:  Variations of a gene (create versions of the same protein) Example: tall & short  Each individual has two alleles for each gene - diploid One allele from each parent (gametes fused) Homologous chromosomes

5. Genes & Alleles  Alleles can be:  Dominant: always shown Tall: “T”  Recessive: Masked or covered up by dominant allele Short: “t”

6. Genotype  Total of all alleles; genetic make-up  Two alleles  Ex: TT, Tt, tt  Genotype types:  Homozygous (same two alleles) Homozygous dominant = TT Homozygous recessive = tt  Heterozygous (different alleles) One of each allele (Tt)

7. Phenotype  Physical appearance of trait  Examples:  Tall, short, straight, curly, etc.

8. Mini-quiz; T = tall; t = short  Tall plant  Possible genotypes?  Phenotype?  Short plant  Possible genotypes?  Phenotype?

9. Sexual Reproduction:  Individuals are diploid – have two alleles for each gene  Human gametes: egg & sperm  Gametes are haploid  Only contain one of each chromosome  Have one allele for each gene  In sexual reproduction, it is totally random which allele for each gene is passed onto offspring

10. One-trait crosses Single Factor Crosses

11. Let’s practice!  Gametes can only have one allele for each gene  Homozygous dominant parent: TT  Gametes: T or T  Homozygous recessive parent: tt  Gametes: t or t  Heterozygote parent: Tt  Gametes: T or t

12. Let’s Practice!  Cross: TT x tt  Determine all possible combinations of gametes One from each parent  How?  Using Punnett square

13. Punnett Squares  Cross: TT x tt  TT gametes: T or T  tt gametes: t or t F1 Genotype: F1 Phenotype: T T t t Tt

14. Punnet Squares  Cross: Tt x Tt  T = tall; t = short  Tt x Tt Gametes from parent #1: T or t Gametes from parent #2: T or t  Make a punnett square representing this cross and its results

15. Tt x Tt TTTt tt Tt T t TT Tt tt

16. F1 cross results  T = tall; t = short  Genotypes: TT, Tt, tt  Genotypic ratio: 1:2:1  Phenotypes: tall, short  Phenotypic ratio: 3: 1

17. Practice Problem  T = tall; t = short  Cross a heterozygous tall plant with a homozygous recessive plant  What are the expected genotypes and phenotypes of the offspring?

18. 7.1 Practice Problems