Where we’ve been:

1. Where we’ve been: • Charles Darwin and his travels (Darwin Notes 1) • Natural Selection (Notes 2) • Moths and Natural Selection Spoons • Evidence for Evolution (Notes 3) • Comparative Anatomy, Biogeography, DNA • Packet, Video, Webquest, Biochemical Comparisions • Mechanisms of Evolution (webquest and this) • Genetic Drift, Sexual Selection, Mutation, Migration, Natural Selection

2. 16.1 GENES AND VARIATION

3. I. “Gaps” in Darwin’s Theory 1. How do VARIATIONS arise? -Variation was one of the key “ingredients” of NATURAL SELECTION - Remember: variation, selection, time - Some variations are better than others, the environment SELECTS those. 2. How are FAVORABLE variations (traits) passed on to offspring?

4. What scientist’s work could have help Darwin with these questions?

5. MENDEL!!! • (Remember, he described INHERITANCE of “factors” in pea plants).

6. + II. Putting it all together! By the 1930s, Mendel and Darwin’s work were combined. Molecular biologists had also discovered that: 1) DNA was the molecule of heredity. DNA determines phenotype. 2) Sources of variation include MUTATION and GENE SHUFFLING

7. We can now describe evolution in GENETIC terms. We can be more specific than “change over time.” • Evolve: change over time • Evolution(in genetic terms)is any CHANGE in the relative FREQUENCY of ALLELES in a population. OR AKA: biological evolution or microevolution A change in genetic composition within a population over generations.

8. Genetic Vocabulary Review • Gene • Trait • Genotype • Allele • Phenotype

9. Vocab: 1. A POPULATION is a group of individuals of the same species that interbreed and reproduce. 2. A GENE POOL is all genes, including different alleles, that are in a population.

10. 3. RELATIVE FREQUENCY is the # of times an allele appears in a population. General Equation: Relative frequency of an allele= # of the certain allele in the population # of TOTAL alleles in the population

11. MAIN IDEA! • Allele Frequency is about finding (# of A’s) (total # of A’s + a’s)

12. Application What is the allele frequency in the mice population

13. Which mice genotypes contain the dominant allele for fur color (B)? • 2, the BB and Bb mice How many dominant alleles are in the homozygous dominant black mouse? The heterozygous mouse? • 2, 1 allelefor brown fur allele for black fur 48% heterozygous black 16% homozygous black 36% homozygous brown

14. ***Relative frequency of a DOMINANT allele = (# homozygous dominant x 2) + (# heterozygous x 1) (# individuals in population x 2) Why multiply the # of individuals by 2? Each individual has two alleles for a trait, one from mom, one from dad. allelefor brown fur allele for black fur 48% heterozygous black 16% homozygous black 36% homozygous brown

15. 2, the Bb and bb mice Which mice genotypes contain the recessive allele (b)? How many recessive alleles are in the heterozygous mouse? The homozygous recessive mouse? 1, 2 allelefor brown fur allele for black fur 48% heterozygous black 16% homozygous black 36% homozygous brown

16. ****Frequency of a RECESSIVE allele= (# homozygous recessive x 2) + (# heterozygous x 1) (# individuals in population x 2) allelefor brown fur allele for black fur 48% heterozygous black 16% homozygous black 36% homozygous brown

17. III. Example: Calculating the relative frequency Example 1: Let's consider a gene with only two alleles. In mice, Black fur color (BB or Bb) is dominant to brown fur color (bb). In a population of 100 mice, 36 mice are homozygous dominant (BB), 48 mice are heterozygous (Bb) and 16 are brown (bb). Relative frequency of B= # of B alleles in the population # of TOTAL alleles in the population Relative frequency of a dominantallele: = (# homozygous dominant x 2) + (# heterozygous x 1) (# individuals in population x 2)

18. Relative frequency of B = (36 x 2) + (48 x 1)= .60 = 60% (100 x 2) = 200 or 36+36+48 = 120 = 60% 100+100 200 How could we figure out the frequency of “b” without doing the big equation? 0.6 + 0.4 =1.0

19. Note that the allele frequencies add up to 1. *This is a law of population genetics: The sum of all allele frequencies will always be equal to 1. This is because 1 represents the frequency of all possible alleles within the population.

20. Frequency of b? Frequency of b = # of b alleles in the population # of TOTAL alleles in the population Frequency of a recessive allele: = (# homozygous recessive x 2) + (# heterozygous x 1) (# individuals in population x 2)

21. Frequency of b= (16 x 2) + (48 x 1) = 80 = 0.4 = 40% (100 x 2) = 200 200 or (16 + 16 + 48) = 80 = 0.4 = 40% (100 +100 ) = 200 Note that the two allele frequencies add up to ONE. 0.6 + 0.4 =1.0

22. Let’s say that these mice have several generations of offspring. We want to know if EVOLUTION has occurred. How would we know? • If the relative frequencies of the alleles CHANGE, then evolution has occurred!

23. IV. 2 Sources of Variation: A Review Clip: Why don't horses have wheels? 1.Mutations are any change in the DNA sequence (AATAC  AATAT) May be caused by: Mistakes during replication Radiation or chemicals in the environment Effects: INCREASE Fitness, DECREASE Fitness, or NO Effect When would a mutation have no effect? Ex: Silent mutation, no change in amino acid sequence

24. When would a mutation that caused a phenotypic change have no effect on fitness? If it were something that did not effect SURVIVAL and REPRODUCTION. Ex. extra finger or extra teeth.

25. 2.Sexual Reproduction (Gene Shuffling) Q: Why don’t you look exactly like your parents? (what were the sources of genetic variation you learned in meiosis?)

26. Meiosis: • Random assortment of genes, random separation of chromosomes (the Law of Independent Assortment). • Crossing Over: exchanging parts of homologous chromosomes

27. REMEMBER! Some variations are better than others, the environment SELECTS those. • The source of variation is on the DNA level!