Decoding Genetics: The How and Why of Heredity

1. GENETICS

2. Genetics-the “How” and “Why” of Heredity • Genetics • study of heredity

3. Heredity=passing of genetic information from parent to offspring (hint…what do you have in common genetically with your parents?)

4. Gene=unit of heredity made up of a specific sequence of DNA that makes a protein that gives us our traits Trait Protein

5. Gene Pool • Total genes in a population at any one time

6. How Does This Stuff Work? • Alleles: • Different versions of a gene for the same trait (distinguishing characteristic or quality) • Example of the alleles for color of butterfly wings:

7. How Does This Stuff Work? • Thanks to Gregor Mendel (Father of Genetics) …we can understand it using his 3 Laws of Inheritance! • Law of Segregation • Law of Dominance • Law of Independent Assortment

8. Law of Segregation • Remember Meiosis??? Genetic recombination & crossing over • Homologous pairs of chromosomes separate during Meiosis…the genes also separate homologouschromosomes sister chromatids sister chromatids

9. Law of Dominance • Allele that controls the trait is called DOMINANT • “Hidden” allele is called RECESSIVE • Recessive trait is only shown when BOTH alleles are recessive • Example:

10. Law of Independent Assortment • Daughter cells receive a mix of alleles • How? • Mix of maternal alleles (from MOM) • Mix of paternal alleles (from DAD)

11. How Do We Know What Alleles You Have? • Can study the actual genetic makeup…this is represented by letters = GENOTYPE

12. How Do We Know What Alleles You Have? • Can use our observations of color, height, shape, etc….this is PHENOTYPE

13. **REMEMBER***

14. Remember…Alleles Occur in Pairs! • Homozygous = SAME (purebred) • 2 identical alleles for same trait • Example: • Heterozygous = DIFFERENT (hybrid) • Non-identical alleles • Example:

15. Should this Dog be called Spot?!?

16. How Can We Figure It Out on Paper? • If we know the alleles, we can use a PUNNETT SQUARE to help determine probability (chance or likelihood of something happening…think of rolling dice) • This will show a MONOHYBRID CROSS • Only look at ONE trait at a time • Mono = 1 • Cross = mate

17. In Order to Study Heredity, We Must Follow the Generations • The original generation we study is the PARENTAL GENERATION (P1) • P generation has offspring called FIRST GENERATION (F1) • If these F1 generation mate and produce offspring, we have SECOND GENERATION (F2)

18. Let’s Try This! • Who can roll their tongue??? • Tongue Rolling = T • Non-tongue Rolling = t • P1 Generation: • TT (Dad) X tt (Mom)

19. P1 Generation • TT (Dad) X tt (Mom) • TT = Homozygous Dominant • tt = Homozygous Recessive Dad Mom Results

20. F1 Generation (if the offspring were to mate…) • Tt X Tt • Tt = Heterozygous Dad Mom Results

21. Let’s take it step by step now… • Step 1: Choose a letter that represents the trait being discussed • C = Dominant allele = green pod color • c = Recessive allele = yellow pod color • Step 2: Write the genetic problem or the genotypes of each parent • Parents = P1 generation = both heterozygous • P1 = C c X C c • ALWAYS write C c NOT c C

22. Step 3: Show the work in a Punnett Square • Step 4: F1 Genotypic Results Step 5: Phenotypic Results

23. **Quick Reminders…just listen…** • Evolution is the result of GENETIC changes that occur in constantly changing environments

24. **Quick Reminders…Just Listen…** • Populations change in response to their environments