1. Heredity Overview
How are genetic characteristics passed on from one generation to the next?

2. Cell Division Chromosomes Mitosis Meiosis
Contains the genetic information that is passed on (made of DNA)
Hominids = 46 chromosomes (23 pairs)
Mitosis
Body (“somatic”) cells  replaces damaged cells
Meiosis
Sex cells (sperm and egg)  creates variation within the species because of the random assortment of chromosomes in the sex cells

3. Genetic Vocabulary Review
Fertilization  joining of egg and sperm
True-breeding  produces offspring identical to themselves
Trait  specific characteristic inherited
Hybrid  offspring of parents with different traits
Gene  chemical factors (DNA) that determine traits
Allele  the different forms of a gene

4. Principle of Dominance
States that some alleles are dominant and others are recessive
Dominant allele  will always exhibit that form of the trait (A)
Recessive allele  will only exhibit if no dominant allele is present; need 2 recessive alleles to show a recessive trait (a)
Homozygous  individuals 2 of the same alleles
Homozygous dominant: AA
Homozygous recessive: aa
Heterozygous  individuals with 2 different alleles (Aa)

5. # of students
Widow’s peak
No widow’s peak
Dimples
No dimples
Freckles
No freckles
Extra digits
Normal digits
Attached earlobes
Unattached earlobes

7. Punnett Squares

9. Segregation of Genes Alleles segregate during gamete production
Phenotype = physical characteristics (tall vs. short
Genotype = genetic makeup (AA, Aa, or aa)
Pure cross  2 parents: one homozygous dominant and one homozygous recessive
Results in F1 offspring
F1 cross  2 parents from the F1 offspring (both are heterozygous)
Results in a phenotypic ratio of 3 tall:1 short
Results in a genotypic ratio of 1 AA:2 Aa:1aa

10. Genes and Probability
Probability – likelihood that a particular event will occur
Flipping a coin once: heads (50% or 1/2); tails (50% or 1/2)
If flipped 3 times in a row = ½ * ½ * ½ = 1/8 (or 0.125)
Probability predicts possible genetic outcomes based on the way alleles segregate in meiosis

11. Mendelian Genetics
In Mendelian genetics, Genes must be able to independently assort
Genes must not influence each other’s inheritance
Independent assortment accounts for the genetic variation in living things

12. Beyond Dominant and Recessive Alleles
Some alleles are neither dominant or recessive, and many traits are controlled by multiple alleles or genes
Incomplete dominance One allele is not completely dominant over the other
Codominance Both alleles contribute to phenotype
Multiple alleles (ex. blood type)
Polygenic traits  controlled by more than one gene (ex. Skin color, eye color, hair color)

13. Genetics and the Environment
The characteristics of organisms  not solely determined by inherited genes
Determined by interaction between genes and the environment
Genes provide a plan for development  how the plan unfolds also depends on the environment

14. Genes and Variation 2 main sources of genetic variation:
Mutations
Gene shuffling during sexual reproduction
Gene pool  all genes (and alleles) that are present in a population
Relative frequency  # of times an allele occurs in a gene pool (given as a percentage)
Evolution is any change in the relative frequency of alleles in a population

15. Evolution as Genetic Change
Evolutionary fitness  an organism’s success in passing genes to the next generation
Evolutionary adaptation  any genetically controlled physiological, anatomical, or behavioral trait that increases ability to pass on genes

16. Natural Selection and Evolution
Natural Selection never acts directly on genes
Works on the entire organism…can only affect which individuals survive and reproduce
If an individual dies  does not pass on genes
ALSO…Individuals do not evolve…Populations evolve as the gene pool changes because of the relative frequency of the alleles changes

17. How did Hominids Evolve?
Natural Selection in not the only source of evolutionary change
Genetic drift 
Individuals that carry a particular allele may leave more descendents BY CHANCE.
Over time, a series of chance occurrences can cause an allele to become common in a population
A new species can result if there is enough of a genetic difference between the original population and the new population

18. The Process of Speciation
Formation of a new species (organisms that breed and produce fertile offspring)
As new species evolve, populations become isolated from one another
Reproductive isolation  members of 2 populations can no longer interbreed and produce fertile offspring

19. Isolating Mechanisms
Behavioral Isolation  differences in courtship or other reproductive strategies that involve behavior
Geographic Isolation  2 populations are separated by geographic barriers
Temporal Isolation  2 or more populations reproduce at different times of the year