1. Inheritance Patterns & Meiosis

2. Incomplete dominance  Phenotype made by blend of the dominant & recessive alleles  Red flower allele + white flower allele = pink flower (ONLY IN HETEROZYGOUS) Japanese 4 O’clocks

3. Incomplete dominance Practice  In some cats the gene for tail length shows incomplete dominance. Cats with long tails (L) and cats with no tails (N) are homozygous for their respective alleles. Cats with one long tail allele and one no tail allele have short tails. For each of the following construct a Punnett square and give phenotypic and genotype ratios of the offspring: a) a long tail cat and a cat with no tail b) a long tail cat and a short tail cat

4. Codominance  Phenotypes made by both alleles showing up at the same time and are equally expressed  Red/Brown allele + white allele = RED/BROWN AND WHITE spotted cow (ONLY IN HETEROZYGOUS!) Roan Cattle

5. CODOMINANCE PRACTICE  Erminette chicken exhibit codominance.. They have feathers that are both black (B) and white (W) but NOT GREY. A heterozygous (BW) Erminette chicken will have both black and white feathers.  A) cross a black feathered chicken with a black and white feathers  B) cross a white feathered chicken with a black feathered chicken

6. Multiple alleles  A gene that is determined by more than two alleles  Blood Type = A, B & i

7. Sex-linked Traits  Disease/disorder caused by a gene that occurs on a sex chromosome (X or Y), usually the X chromosome  Examples of X-linked (recessive)  Hemophilia  Colorblindness  Duchenne muscular dystrophy  Examples of Y-linked  Azoospermia  Retinitis pigmentosa

8. Sex-linkage and Inheritance Alleles: X with superscript indicating trait Y with no superscript (unless Y linked) Applies to sex-linked disorders ONLY!

9. Sex-linked Practice  Hemophiliac male marries a normal healthy female  H & h superscript  Colorblind male marries colorblind female  C & c superscript

10. Polygenic inheritance  Traits that are controlled by 2 or more genes – results in wide range of phenotypes  Most human traits are polygenic

11. Genes & Environment  Environmental conditions can affect gene expression and influence genetically controlled traits  Ex: Western white butterfly SpringSummer

12. Do Now  The lubber grasshopper is a very large grasshopper, and is black with red and yellow stripes. Assume that red stripes are expressed from the homozygous RR genotype, yellow stripes from the homozygous rr genotype, and both from the heterozygous genotype. What will be the phenotypic ratio resulting from a cross of two grasshoppers, both with red and yellow stripes (red : both : yellow)? homozygousgenotypeheterozygousphenotypic ratio  A naturalist visiting an island in the middle of a large lake observes a species of small bird with three distinct types of beaks. Those with short, crushing beaks (BB) consume hard shelled nuts, those with long, delicate beaks (bb) pick the seeds from pine cones, and those with intermediate beaks (Bb), consume both types of seeds though they are not as good at either. Cross a short beaked bird with a intermediate beaked bird and give the phenotypic ratio for the offspring (short : intermediate : long) ?

13. Do Now  What is the difference between anaphase I and anaphase II in meiosis ? Look at your POGIL!

14. Meiosis = makin’ gametes! http://www.youtube.com/watch?v=rB_8dTuh73c

15. Chromosomes  Humans have 46 chromosomes organized into 23 pairs  23 chromosomes from mom  23 chromosomes from dad  Pairs are homologous  46 chromosomes = 2N or diploid  23 chromosomes = N or haploid

16. Meiosis  Process that makes haploid (N) cells or gametes (sex cells)  Divided into 2 phases:  Meiosis I  Meiosis II

17. Meiosis I  Interphase  chromosomes copied  46 chromosomes  46 replicated chromosomes (92 chromatids)

18. Prophase I  Condensed & replicated chromosomes match into homologous pair called tetrad  Process is referred to as synapsis  Crossing over occurs

19. Crossing over  Homologous chromosomes overlap at chiasma  Alleles are exchanged between chromosomes  Increased genetic diversity!

20. Metaphase I  Spindle fibers attach to tetrad chromosomes in middle of cell  Independent assortment occurs!  Random way paternal and maternal chromosomes with the homologous pair line up at the metaphase plate.  Increases variation!

21. Anaphase I  Homologous pairs separated by spindle fibers

22. Telophase I and Cytokinesis  New nuclear membrane forms and cells split

23. MEIOSIS II VERY IMPORTANT!!  CHROMOSOMES DO NOT REPLICATE THIS TIME!!

24. Prophase II  Chromosomes condense  Nuclear envelope dissolves  Spindle fibers form

25. Metaphase II  Chromosomes line up in the middle of the cells

26. Anaphase II  Paired chromatids separate

27. Telophase II and Cytokinesis  Nuclear membrane reforms and cytoplasm splits

28. Problems with Meiosis  Non-disjunction: chromosomes do not divide evenly between daughter cells  Can lead to embryo with trisomy (three chromosomes of a particular type) or monosomy (only one chromosome of a particular type)

29. Klienfelter’s Syndrome  Male with an extra X chromosome  (XXY)  Signs/Symptoms  More female body characteristics  Low muscle tone

30. Down Syndrome  Trisomy (3 copies) of chromosome 21  Signs/Symptoms  Low IQ  Slanting eyes & small mouth  Delayed language and speech development

31. Turner’s Syndrome  Female with only 1 X chromosome (X)  Signs/Symptoms  Short stature  Infertile  Lack of sexual development  Low IQ  Abnormal bone development

32. Meiosis Summary  Meiosis I  Start: 1 cell with 46 chromosomes (23 homologous pairs)  2N or diploid  End: 2 cells with 23 chromosomes + a copy of those same 23 chromosomes  N or Haploid  Meiosis II  Start: same as end of meiosis I  End: 4 cells with 23 chromosomes (and no copies)  N or haploid

33. Comparing mitosis & meiosis  As you watch the video, identify as many similarities and differences between mitosis and meiosis as you can: http://www.youtube.com/watch?v=zGVBAHAsjJM http://www.youtube.com/watch?v=zGVBAHAsjJM MitosisMeiosis No change in chromosome number Creates diploid cells Resulting cells are genetically identical Results in 2 cells Chromosome number cut in half Creates haploid cells Resulting cells are genetically different Results in 4 cells Similarities: Form of cell division Have same stages with same general events: PMAT-C

35. Fertilization  Sperm and egg join to form a zygote  New combination of alleles  Gametes = haploid  Zygote = diploid Sperm (23) + egg (23) = zygote (46)