1. Lesson Overview Lesson Overview The Work of Gregor Mendel What do you already know about Gregor Mendel? What do you know about genetics? What questions do you have about genetics?

2. Lesson Overview Lesson Overview The Work of Gregor Mendel Gregor Mendel 1822 in Czech Republic Priest Studied math and science Taught in a monastery In charge of monastery gardens

3. Lesson Overview Lesson Overview The Work of Gregor Mendel Peas Why were they studied? Fertilization/Pollination – Mostly self-pollinating – Mendel’s experiments True-breeding plants Forcibly cross-pollinated Created hybrids Looked at several traits

4. Lesson Overview Lesson Overview The Work of Gregor Mendel Round and Wrinkled True-breeding parents, P generation Offspring, F1 generation – Only round peas Similar results with other traits Conclusion – Traits passed from parents – Genes – Alleles

5. Lesson Overview Lesson Overview The Work of Gregor Mendel Dominant allele Recessive allele

6. Lesson Overview Lesson Overview The Work of Gregor Mendel Crossing F1 Generations Self-pollination of F1 Produced F2 ¼ exhibited recessive traits Conclusion – Alleles separate in sex cells (gametes) – One allele from each parent

7. Lesson Overview Lesson Overview The Work of Gregor Mendel Inheritance of Genes Mathematical model Assumptions Tall vs. short – Dominant (T) – Recessive (t) – Genotype – Phenotype – Homozygous – Heterozygous TT Tt = tT tt

8. Lesson Overview Lesson Overview The Work of Gregor Mendel Punnett Squares Mendel’s first cross (round x wrinkled) True-breeding = homozygous 1 allele from each parent 2 alleles in a genotype

9. Lesson Overview Lesson Overview The Work of Gregor Mendel Mendel crossed true-breeding yellow and green peas. All the offspring were yellow. – Write the genotype for these parents and the offspring. Use a Punnett square to help with the offspring. – Now cross the F1 with itself and write the genotypes of possible offspring along with the phenotypes. Use a Punnett square.

10. Lesson Overview Lesson Overview The Work of Gregor Mendel What about two traits at once? Will one allele affect the other? – Short always yellow? – Get new combinations? Mendel – Homozygous plants – Round, yellow x wrinkled, green plants – Assume: independence

11. Lesson Overview Lesson Overview The Work of Gregor Mendel Round, yellow x wrinkled green Genotypes: What alleles?

12. Lesson Overview Lesson Overview The Work of Gregor Mendel F2 Genotype Alleles?

13. Lesson Overview Lesson Overview The Work of Gregor Mendel Independent Assortment Genes for different traits separate independently during gamete formation Not all tall plants have yellow seeds Some genes are linked to each other – Not in those studied by Mendel

14. Lesson Overview Lesson Overview The Work of Gregor Mendel Other Patterns of Inheritance Peas are simple Incomplete dominance – Neither dominant nor recessive – Mixture phenotype – Plants Red (RR) White (rr) Pink (Rr) Red flower x Pink flower

15. Lesson Overview Lesson Overview The Work of Gregor Mendel Codominance – Both alleles expressed – Blood types – Chicken feathers Multiple alleles – More than 2 forms – Blood types – Rabbit coat color Polygenic traits – Controlled by more than 1 gene – Skin and eye color

16. Lesson Overview Lesson Overview The Work of Gregor Mendel In Chaparral llamas, brown coat color and blue eyes are dominant to white coat color and brown eyes. A heterozygous (for both traits) female llama breeds with a homozygous recessive male llama. Draw a Punnett square and describe the fraction of each phenotype possible in the offspring.

17. Lesson Overview Lesson Overview The Work of Gregor Mendel Cells and Chromosomes Somatic cells – Most cells in the body – Reproduce through mitosis – 46 chromosomes, 23 pairs – Diploid (2n) Gamete cells – Reproductive cells; sperm and egg – Unite with another cell in fertilization – 23 chromosomes, no pairs – Haploid (n)

18. Lesson Overview Lesson Overview The Work of Gregor Mendel Diploid vs. haploid – Why does there need to be a difference? – If 2N = 8, then N = – If N = 12, then 2N = How does this relate to genes? – DNA – Chromosomes – Homologous chromosomes

19. Lesson Overview Lesson Overview The Work of Gregor Mendel Meiosis 2N  N 2 parts: meiosis I and meiosis II Meiosis I – DNA replicates during interphase – Diploid – Prophase I Similar to mitosis Homologous chromosomes pair  tetrad Crossing over can occur

20. Lesson Overview Lesson Overview The Work of Gregor Mendel Metaphase I – Homologous chromosomes line up Anaphase I – Separate homologous chromosomes Telophase I – Nuclear membrane re-forms Cytokinesis Results – 2 daughter cells – Haploid or diploid? – May not be genetically identical

21. Lesson Overview Lesson Overview The Work of Gregor Mendel Meiosis II No replication in interphase Prophase II – Chromosomes visible Metaphase II – Chromosomes line up Anaphase II – Chromatids separate Telophase II Cytokinesis

22. Lesson Overview Lesson Overview The Work of Gregor Mendel Results – 4 cells from original 1 – Each haploid – ½ genetic information of parent Males – all 4 cells used Females – 1 out of 4 used – Meiosis II doesn’t occur until fertilization Fertilization – Egg and sperm unite – Diploid zygote – Goes through mitosis rapidly, repeatedly

23. Lesson Overview Lesson Overview The Work of Gregor Mendel Mitosis vs. Meiosis Both – require DNA replication first Mitosis – Daughter cells diploid – Produces 2 cells Meiosis – Daughter cells haploid – Produces 4 cells

24. Lesson Overview Lesson Overview The Work of Gregor Mendel Genes and the Environment Effect gene expression Western white butterfly – Wing color varies – Spring – darker – Need specific body temp. to fly – Absorb more sunlight to be warmer

25. Lesson Overview Lesson Overview The Work of Gregor Mendel Karyotype Genome Karyotype – Definition 23 pairs, 46 chromosomes

26. Lesson Overview Lesson Overview The Work of Gregor Mendel Sex vs. Autosome Sex – 2 chromosomes – Female – Y XY = male Smaller Male specific genes Autosomal – 44 chromosomes

27. Lesson Overview Lesson Overview The Work of Gregor Mendel How are traits inherited? Mendelian patterns Dominant vs. recessive Codominant Multiple alleles Sex-linked – Sex chromosomes – Y  only in males – X  both sexes – Recessive traits – Example

28. Lesson Overview Lesson Overview The Work of Gregor Mendel Pedigree Family tree Circles vs. squares Determine – Dominance – Sex-linked

29. Lesson Overview Lesson Overview The Work of Gregor Mendel Define – Karyotype – Genome – Pedigree What is an example of a sex-linked trait and why are sex-linked traits different than other traits? What is the difference between sex and autosomal chromosomes?

30. Lesson Overview Lesson Overview The Work of Gregor Mendel Genetic Disorders Sickle cell – Recessive – Irregularly shaped RBC – Stick together – Don’t carry O 2 as well – Painful – No cure – Advantages Carriers Malaria resistance

31. Lesson Overview Lesson Overview The Work of Gregor Mendel Cystic fibrosis – Recessive – Necessary protein destroyed – Digestive and respiratory problems – Advantage Europeans Block typhoid bacterium Huntington’s disease – Dominant allele – Different protein – Mental deterioration

32. Lesson Overview Lesson Overview The Work of Gregor Mendel Chromosome Disorders Nondisjunction Down syndrome – Trisomy 21 Turner’s syndrome –X–X Klinefelter’s syndrome – XXY

33. Lesson Overview Lesson Overview The Work of Gregor Mendel Gene Linkage Mendel – Independent assortment of genes Thomas Hunt Morgan – Fruit fly research – Traits inherited together – Genes stay together if on same chromosome

34. Lesson Overview Lesson Overview The Work of Gregor Mendel Gene Mapping Alfred Sturtevant – Fruit flies – Location of genes on chromosome