1. 5/2 Warm-up Pick up handouts Log-on HW: Allele Frequency WS Agenda
Quiz: Evolution Vocab
Notes: Genes and Variety
WS: Allelic Frequencies
HW: Allele Frequency WS

2. 16.1 Genes and Variation

3. I. “Gaps” in Darwin’s Theory 1. How do VARIATIONS arise
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 now describe evolution in GENETIC terms. We can be more specific than “change” over time.
Evolution (in genetic terms) is any CHANGE in the relative FREQUENCY of ALLELES in a population.

8. 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.

9. 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

10. 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
48% heterozygous black
16% homozygous black
36% homozygous brown
allele for brown fur
allele for black fur

11. ***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.
48% heterozygous black
16% homozygous black
36% homozygous brown
allele for brown fur
allele for black fur

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

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

14. 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 dominant allele
= (# homozygous dominant x 2) + (# heterozygous x 1)
(# individuals in population x 2)

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

16. Note that the two allele frequencies add up to 1
Note that the two 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.

17. 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)

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

19. Let’s say that these mice have several generations of offspring
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, evolution has occurred!

20. 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

21. 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.

22. 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?

23. Meiosis:
random assortment of genes, random separation of chromosomes
(law of independent assortment).
Crossing over: exchanging parts of homologous chromosomes

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