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Les son 17: P atterns of Inheritance

Les son 17: P atterns of Inheritance. blackwellpublishing.com. Roots: Di = 2 mono = 1 Homo = same Hetero = different Hemo = blood. www.microscopy-uk.org.uk/mag/imgjul06/Image14.jpg. www.purplemoon.com/Stickers/peas-earth.jpg. Gregor Mendel.

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Les son 17: P atterns of Inheritance

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  1. Lesson 17: Patterns of Inheritance blackwellpublishing.com Roots: Di = 2 mono = 1 Homo = same Hetero = different Hemo = blood www.microscopy-uk.org.uk/mag/imgjul06/Image14.jpg www.purplemoon.com/Stickers/peas-earth.jpg

  2. Gregor Mendel • Modern genetics began in the mid-1800s in an abbey garden, where a monk named Gregor Mendel documented inheritance in peas • used good experimental design • usedmathematicalanalysis • collected data & counted them • excellent example of scientific method http://joefelso.files.wordpress.com/2007/04/mendel2.jpg

  3. Mendel’s work Pollen transferred from white flower to stigma of purple flower • Bred pea plants • cross-pollinate true breeding parents • raised seed & then observed traits • allowed offspring to self-pollinate& observed next generation anthers removed all purple flowers result self-pollinate ?

  4. Mendel collected data for 7 pea traits Each trait is represented by a specific allele on a specific chromosome. Allele = genes that determine a specific trait. http://www.bio.miami.edu/~cmallery/150/mendel/7traits.jpg

  5. true-breeding purple-flower peas true-breeding white-flower peas 100% purple-flower peas 1st generation (hybrids) 100% 75% purple-flower peas 25% white-flower peas 3:1 2nd generation X Parents self-pollinate

  6. What did Mendel’s findings mean? • Some traits mask others • purple & white flower colors are separate traits that do not blend • purple x white ≠ light purple • purplemaskedwhite • dominant allele • functional protein • affects characteristic • masks other alleles • recessive allele • no noticeable effect • allele makes a non-functioning protein mutant allele malfunctioningprotein allele producingfunctional protein homologouschromosomes mygenetic.wordpress.com

  7. X P purple white F1 all purple Genotype vs. phenotype • Difference between how an organism “looks” & its genetics • phenotype • Form of the trait that gets expressed“what you see” • genotype • An organism’s actual alleles Explain Mendel’s results using …dominant&recessive …phenotype&genotype

  8. Inheritance of genes • On the chromosomes passed from Mom & Dad to offspring are genes • may be same information • may be different information eye color (blue or brown?) eye color (blue or brown?)

  9. Remember how Meiosis separates the alleles into sex cells? palaeos.com This separation is called the Law of Segregation.

  10. Effect of genes • Genes come in different versions • brown vs. blue eyes • brown vs. blonde hair • Alleles = different forms of a gene

  11. Homozygous dominant = AA Homozygous recessive = aa Heterozygous = Aa Homozygous = same Heterozygous = different aa rr XY Ss Ww Tt Aa Yy BB RR Ee bb AB Bb

  12. Genes affect how you look… X bb BB Bb Bb Bb Bb Where did the blue eyes go??

  13. X bb Bb Bb Bb bb bb Why did the blue eyes stay??

  14. X Bb Bb bb BB or Bb BB or Bb BB or Bb Where did the blue eyes come from??

  15. Genes come in “versions” • brown vs. blue eye color • Alleles (different forms of a gene) • Alleles are inherited separately from each parent • brown & blue eye colors are separate & do not blend • either havebrown or blue eyes, not a blend • Some alleles mask others • brown eye color masked blue

  16. eye color (blue?) hair color hair color How does this work? • Paired chromosomes have same kind of genes • but may be different alleles eye color (brown?)

  17. Traits are inherited as separate units • For each trait, an organism inherits 2 copies of a gene, 1 from each parent • a diploid organism inherits 1 set of chromosomes from each parent • diploid = 2 sets (copies) of chromosomes 1 from Mom homologous chromosomes 1 from Dad

  18. B B B b b b BB Bb bb Making gametes BB = brown eyes bb= blues eyes Bb= brown eyes Dominant = can mask others  brown is dominant over blue  blue is recessive to brown Recessive = can be hidden by others Remember meiosis!

  19. How do we say it? B B B b b b BB Bb bb 2 of the same alleles Homozygous BB = brown eyes bb= blues eyes homozygous dominant homozygous recessive 2 different Heterozygous Bb= brown eyes

  20. Punnett squares B b B b Bb x Bb male / sperm X BB Bb female / eggs Bb bb

  21. Genetics vs. appearance • There can be a difference between how an organism looks & its genetics • appearance or trait = phenotype • brown eyes vs. blue eyes • genetic makeup = genotype • BB, Bb, bb 2 people can have the same appearance but have different genetics: BB vs Bb

  22. B B B b BB Bb http://designora.com/wp-content/uploads/2009/11/32-brown-eyes.jpg Genetics vs. appearance How were these brown eyes made? eye color (brown) eye color (brown) eye color (brown) eye color (blue) vs.

  23. PP pp x X P purple white F1 all purple Making crosses • Can represent alleles as letters • flower color alleles  P or p • true-breeding purple-flower peas  PP • true-breeding white-flower peas  pp Pp

  24. PP 25% male / sperm P p Pp 50% 75% P Pp female / eggs pp p 25% 25% Punnett squares Aaaaah, phenotype & genotypecan have different ratios 1st generation (hybrids) Pp x Pp % genotype % phenotype PP Pp Pp pp 1:2:1 3:1

  25. http://crittergeek.com/wp-content/uploads/2006/11/calico.jpg http://pixdaus.com/pics/12072579159eXGQHR.jpg Beyond Mendel’s Lawsof Inheritance http://www.drstandley.com/images/health%20topics/Acromegaly2.jpg http://staff.tuhsd.k12.az.us/gfoster/standard/3head.gif

  26. Extending Mendelian genetics • Mendel worked with a simple system • peas are genetically simple • most traits are controlled by single gene • each gene has only 2 version • 1 completely dominant (A) • 1 recessive (a) • But its usually not that simple! mac122.icu.ac.jp

  27. Incomplete dominance • Hybrids have “in-between” appearance • RR = red flowers • rr = white flowers • Rr = pink flowers • make 50% less color RR WW RW http://www.mnstate.edu/ www.99andbarry.com www.margaretaflowers.com RR Rr rr

  28. 100% pink flowers 1st generation (hybrids) 100% 25% red 50% pink 25% white 1:2:1 2nd generation Incomplete dominance X true-breeding red flowers true-breeding white flowers P self-pollinate

  29. RR 25% 25% male / sperm R W RW 50% 50% R RW female / eggs WW W 25% 25% Incomplete dominance RW x RW % genotype % phenotype 1:2:1 1:2:1

  30. Codominance • Equal dominance • Chickens • A black-feathered chicken is crossed with a white-feathered chicken. • All of the babies are white with black speckling. • Both white and black show up equally. = x www.self-sufficient-life.com /echotig8.files.wordpress.com www.harvestofhistory.org

  31. More Codominance… x www.smartpawsacademy.com /z.about.com

  32. Multiple Alleles • More than one allele to select from. • Blood “types” can be A, B, AB, or O. • The alleles to make these types include A, B and i. • “i” is the recessive allele and A and B are both dominant. • So to get… • Type A you must have AA or Ai • Type B you must have BB or Bi • Type AB you must have AB • Type O you must have ii

  33. BLOOD Antigens are tiny receptors on the outside of the blood cell that matches the “type.” Multiple Alleles Blood cells have antigens and antibodies. Antibodies are what the cell doesn’t like (which is anything different from the “type.”)

  34. Blood Types Multiple Alleles A B Anti-A Anti-B Type A Type B A B A B Antigens (none) A B Type O Type AB B Anti-A and B none A

  35. Genetics of Blood type Multiple Alleles

  36. One gene : Many effects • The genes that we have covered so far affect only one trait • But most genes are affect many traits • 1 gene affects more than 1 trait • dwarfism (achondroplasia) • gigantism (acromegaly) www.lifeinthefastlane.ca dymaxionweb.com /mentalfloss.cachefly.net

  37. Acromegaly: André the Giant lat34.com

  38. Inheritance pattern of Achondroplasia Aa x aa Aa x Aa library.thinkquest.org a a A a  Aa A Aa A AA Aa a a aa aa Aa aa 50% dwarf:50% normal or1:1 67% dwarf:33%normalor2:1

  39. Many genes : One trait Polygenic =“many genes” • Polygenic inheritance • additive effects of many genes • humans • skin color • height • weight • eye color • intelligence • behaviors www.scientificamerican.com

  40. Human skin color Polygenic =“many genes” • AaBbCc x AaBbCc • range of shades • most children = intermediate skin color • some can be very light & very dark

  41. Albinism Johnny & Edgar Winter melanin = universal brown color theglenblog.blogspot.com cnb.uam.es www.heartlandhunters.com Albinism is the absence of pigment. albinoAfricans xenophilius.files.wordpress.com

  42. Coat color in other animals • 2 genes: E,eandB,b • color (E) or no color (e) • how dark color will be: black (B) or brown(b) E–bb eebb eeB– E–B–

  43. Environment effect on genes www.saskschools.ca • Phenotype is controlled by both environment & genes Coat color in arctic fox influenced by heat sensitive alleles /www.grahamrollason.co.uk /images.pictureshunt.com Color of Hydrangea flowers is influenced by soil pH s3.amazonaws.com wxyc.org Human skin color is influenced by both genetics & environmental conditions

  44. SEX and GENES • Women & men are very different, but just a few genes create that difference • In mammals = 2 sex chromosomes • X & Y • 2 X chromosomes = female: XX • X & Y chromosome = male: XY X X X Y

  45. Sex chromosomes

  46. Sex-linked traits • Sex chromosomes have other genes on them, too • especially the X chromosome • hemophilia in humans • blood doesn’t clot • Duchenne muscular dystrophy in humans • loss of muscle control • red-green color blindness • see green & red as shades of grey X X X Y

  47. HH XHXH XHXh XHXh XHXh Hh XH XHY XHY XhY Xh male / sperm XH Y XHXH XHY XH XHY XH female / eggs Y Xh XhY XHXh sex-linked recessive x 2 normal parents, but mother is carrier

  48. library.thinkquest.org

  49. Most Common AlleleDominant or Recessive Either One! • Because an allele is dominant does not mean… • it is better, or • it is more common Polydactyly dominant allele accessexcellence.org biocrawler.com thelastoutpost.com

  50. Polydactyly individuals are born with extra fingers or toes the allele for >5 fingers/toes is DOMINANT & the allele for 5 digits is recessive stanford.wellsphere.com Recessive allele far morecommon than dominant  only 1 individual out of 500 has more than 5 fingers/toes  so 499 out of 500 people are homozygous recessive (aa) absurdintellectual.com

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