1. Inheritance in the biology sense involves the genes and thus the traits that an offspring receives from it’s parents.

2. Gregor Mendel’s Peas Mendel was an Austrian monk, who in the 1800’s served as a teacher and a amateur scientist. Worked with peas to discover the fundamental basis for our current understanding of genetics First worked with “true-breeding” plants. True-breeding are self pollinators, they would be exactly like the original

3. Genes and Dominance A trait is a specific characteristic that varies from individual to individual. In Mendel’s peas, traits included seed shape and color, seed coat color, pod shape and color, flower position, and plant height P (parental generation) F1 (first offspring) Hybrids=offspring of crosses between parents with different traits

4. Genes and Dominance II When Mendel cross-bred peas with different traits, he found that the traits were not blended, but that the offspring had the characteristics of one of the parents. 2 Conclusions of Mendel’s initial work- Biological inheritance is passed down from generation to generation. (Genes are the chemical factors that do this and different forms of a gene are called alleles) Some alleles are dominant and others are recessive (If the dominant allele is present, then it always shows up, but the recessive trait will not show up if the dominant gene is present)

5. Segregation of Plants Mendel’s next question: What happened to the recessive gene? Did it disappear or what it still present? Next experiment: Cross the F1 plants to themselves to get an F2 generation. Results: the recessive trait reappeared. The recessive trait showed up in ¼ of the new plants. Question: Why did the trait disappear in one generation, then reappear in the next generation?

6. Explanation of the experiment The alleles for tallness and shortness must have somehow separated (segregated) during the fomation of gametes (sex cells)

7. How genes are represented. Dominant genes are represented by capital letters, recessive by lower case. Examples: TT=tall plant, because T represents the dominant gene Tt=is also tall tt= short

8. Probability and Punnett Squares Punnett Squares can be used to predict the probability of genetic crosses. Homozygous -2 identical alleles (TT, tt) Heterozygous-2 different alleles (Tt) Phenotype-how the trait is actually displayed by the organisms (plant is tall or short) Genotype (the actual genetic makeup for a trait, such as TT, Tt, or tt)

9. Probability Flip a coin once, what are the chances of any particular outcome? Flip again, what are the chances of getting the same result as the first time? What happens to the results with more trials? Does the previous trial have any impact on the next one?

10. Simple Punnett Square can be used to predict outcomes

11. Independent Assortment The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes R-round r-wrinkled Y-yellow y-greenF1 cross RRYY x rryy

12. F2 cross RrYy x RrYy Possibilities include: RY, Ry, rY, ry F2 cross

13. Ratio of traits In a 2 factor cross, the ratio of visible traits (phenotypes) will be close to the 9:3:3:1 ratio

14. Principle of Independent Assortment Genes for different traits can segregate independently during the formation of gametes. In other words, inheritance of some traits has nothing to do with inheritance of others

15. Summary of Mendel’s Work Genes control inheritance and these are provided by parents If multiple genes control a trait, one gene may be dominant, others recessive In most organisms, each adult has 2 copies of each gene, one from each parent and the genes segregate during gamete formation The alleles for each gene usually segregate independently of one anther

16. Not as simple as we might like! Mendel’s work was did not lead to the formation of biological laws because it isn’t that simple! Darn! Some alleles are neither dominant nor recessive, and many traits are controlled by multiple alleles or genes

17. Incomplete dominance When 2 traits, (RR-red, WW-white) in flowers produces a heterozygous genotype with a blended phenotype (RW = pink flowers) Neither trait is really dominant, but produces an “in between” result

18. Codominance Similar to Incomplete Dominance with both alleles contributing to the phenotype of the organism Ex. Black feather chickens crossed with white feathered chickens result in speckled feathered chickens In cows, Allele for brown hair is codominant with the allele for white hair, resulting in roan (speckled)

19. Multiple Alleles Some genes have more than 2 alleles (multiple alleles) Example: Color of rabbit fur. 4 different colors possible from the multiple alleles

20. Polygenic Traits Traits controlled by interaction of many genes. Example: Human skin color is partially controlled by several genes and thus is a polygenic trait

21. Applying Mendel’s Principles Mendel’s discoveries apply to more than plants. Fruit Flies are used often in genetics studies because they have easy to observe traits, such as eye color and wing shape, and they reproduce quickly. Mendel’s work applies to humans also. Albinism is a recessive trait for skin color. 2 heterozygous, non- albino parents have a 1 in 4 chance of having an albino child.

22. Meiosis We know that:Each new organism must get a single copy of each of it’s genes from each parent We know that: When each organism produces it’s own gametes, those sets of genes must separate so that each gamete contains only 1 set of the genes. Meiosis is the process by which the number of chromosomes in each cell is cut in ½ by the separation of homologous (matched) chromosomes in a diploid(both sets of chromosomes) cell

23. Example-Drosophila (fruit flies) Adult Drosophila has 8 chromosomes (4 pair of homologous chromosome, 4 from each parent) An adult drosophila is diploid-2N(complete set of chromosomes) In Drosophila, diploid = 8, that is, 2N=8 Reproductive cells in Drosophila are haploid (1 set of chromosomes. The haploid number for Drosophila is 4 (N=4)

24. Phases of Meiosis-2 distinct phases Meiosis I (stage 1) Each chromosome is replicated Each chromosome pairs with it’s corresponding homologous chromosome to form a tetrad (4 chromosomes in a tetrad) Crossing-over may occur between paired chromosomes. Crossing-over involves an exchange of alleles between homologous chromosomes. 2 new cells are formed and each new cell has 4 “reshuffled” chromosomes

25. Meiosis II The second meiotic division DOES NOT involve chromosome replication. When the cells divide again, each new cell contains the haploid number of cells When gametes form (sperm & egg) the egg cells get the majority of the cytoplasm.

27. Mitosis & Meiosis Mitosis results in 2 genetically identical diploid cells Meiosis results in 4 genetically different haploid cells http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter28/ animation__how_meiosis_works.html http://highered.mcgraw- hill.com/sites/0072495855/student_view0/chapter28/ animation__how_meiosis_works.html http://www.youtube.com/watch?v=D1_-mQS_FZ0

28. What are the differences? Meiosis

29. Gene Linkage Traits that are inherited together, located on the same chromosome Examples of sex-linked traits are red-green color blindness and some types of hemophilia