Observable Patterns of Inheritance

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Observable Patterns of Inheritance. Edited by: R. LeBlanc, M.S. Mountain Pointe High School 2012. Starr/Taggarts Biology: The Unity and Diversity of Life , 9e Chapter 11. Charles Barkley. Tom Cruise. What do Charles Barkley and Tom Cruise have in common? (hint: check out their ears). - PowerPoint PPT Presentation


<ul><li><p>Observable Patterns of InheritanceStarr/Taggarts Biology: The Unity and Diversity of Life, 9eChapter 11Edited by: R. LeBlanc, M.S.Mountain Pointe High School2012</p></li><li><p>Fig. 11.1, p. 174Tom CruiseCharles BarkleyGregor MendelJoan ChenWhat do Charles Barkley and Tom Cruise have in common? (hint: check out their ears).</p></li><li><p>Terms Used in GeneticsGenesAllelesHybridHomozygousHeterozygousDominantRecessiveGenotypePhenotypeGenerationsP, F1, F2</p></li><li><p>Plant Reproductive Organs</p></li><li><p>GAMETES - the male or female sex cells. In plants, the sperm is the male sex cell (found in pollen grains), and the ovule (egg) is the female sex cell.PISTIL female reproductive structure.STAMEN male reproductive structure.FERTILIZATION- the uniting of the male and female gametes within the flower. POLLINATION - The transfer of pollen from the anther to the pistil, usually by wind, water, or insects. CROSS-POLLINATION - transferring the pollen from one plant to another plant.Plant Reproductive Terms </p></li><li><p>Mendel identified seven traits in his garden peas that were easily studied:SEED SHAPESEED COLORPOD SHAPEPOD COLORFLOWER COLORFLOWER POSITIONSTEM LENGTHroundwrinkledyellowgreeninflatedwrinkledgreenyellowpurplewhiteaxialterminaltalldwarfHe carefully isolated pure breeding varieties before experimenting with crosses between different varieties.</p></li><li><p>Mendels Insight Into Patterns of Inheritance Mendels Experimental ApproachGarden pea plantCross pollinationWhat are the advantages of SELF cross pollination?What is the advantage of using pea plants?How did Mendel control his experiments?</p></li><li><p>Mendels Experiment</p></li><li><p>Mendel concluded that each organism has two factors (alleles) for each trait.</p><p>He performed crosses with seven different pairs of traits (for example, pure-breeding purple-flowered plants crossed with pure-breeding white-flowered plants). In every case he found that one trait disappeared from the F1 generation only to reappear in the F2 generation plants! </p><p>This is explained by the Rule of Dominance which will be demonstrated in the next two examples:</p></li><li><p>Mendels Theory of SegregationMonohybrid crossGene segregationWhat do you notice about the alleles of both parents?What do the letters A &amp; a stand for? (the font of the letters)What are diploid gamete cells? Haploid?Why are the final gamete cells haploids?What does the fertilized zygote traits represent? (check the alleles)</p></li><li><p>Probability and Punnet SquaresA possibility of outcomes and crossesTest crossesUnknown genotype crossed with homozygous recessive</p></li><li><p>Mendels Monohybrid CrossPure White FlowerPure Purple FlowerWhat traits (genotype) do F1 offspring have?</p></li><li><p>Mendels Monohybrid CrossWhat percentage of the second generation are purple? White?What % are pure purple? White?If you planted four first generation seeds , how many of these seeds will be purple flowers in the 2nd generation?</p></li><li><p>Chapter 9Mendels ConclusionsSection 1 Mendels Legacy</p></li><li><p>Trait StudiedDominant FormRecessive FormF2 Dominant-to- Recessive RatioSEED SHAPESEED COLORPOD SHAPEPOD COLORFLOWER COLORFLOWER POSITIONSTEM LENGTH2.96:13.01:12.95:12.82:13.15:13.14:12.84:1787 tall277 dwarf651 long stem207 at tip705 purple224 white152 yellow428 green299 wrinkled882 inflated6,022 yellow2,001 green5,474 round1,850 wrinkledFig. 11.5, p. 178To get the ratios on the right to all be approximately equal, what do we know about the P1 plants?What do you notice about the number of plants studied?How did Mendel decide which of the traits were dominant? Recessive?Why arent the ratios exactly 3:1?</p></li><li><p>Independent Assortment</p></li><li><p>In-text, p. 180AABBaabbxAaBbABABababTRUE-BREEDING PARENTS:GAMETES:F1 HYBRID OFFSPRING:purple flowers, tallwhite flowers,dwarfWhat are the phenotype ratios of all the offspring resulting from the cross of these 2 parents? Genotype?ALL F1 OFFSPRING: PURPLE TALLGENOTYPE: AaBbWhat about the phenotype ratio of the offspring of the F2 generation? 9 : 3 : 3: 1</p><p>http://www.biology.arizona.edu/mendelian_genetics/mendelian_genetics.htmlUse the website above for practice genetics problems.</p></li><li><p>Fig. 11.9, p. 1811/41/41/41/41/41/41/41/4AABBpurple-floweredtall parent(homozygousdominant)aabbwhite-flowereddwarf parent(homozygousrecessive)F1 OUTCOME: All F1 plants purple-flowered, tall(AaBb heterozygotes)meiosis, gamete formationAaBbAaBbPossible outcomes of cross-fertilizationAaBbaabbAabbaaBbAABBAABbAaBBAaBbAABbAAbbAaBbAabbAaBbaaBBaaBbAaBB1/161/161/161/161/161/161/161/161/161/161/161/161/161/161/161/16</p></li><li><p>Theory in Modern FormIndependent AssortmentGametes require genes independently of how other pairs of genes were sorted outVariety of Offspring</p></li><li><p>A cross where one allele does not completely hide or mask the other producing a blended appearance in the phenotype.Example: In snapdragons, pure red crossed with pure white produce pink!INCOMPLETE DOMINANCE </p></li><li><p>CODOMINANCETwo non-identical alleles of a pair specify two different phenotypes yet one cannot mask the other and both are expressed .</p></li><li><p> Multiple AllelesMore than two alleles in a population for a given trait.Example: human blood types.3 alleles: A,B,O.What do the letters A, B &amp; O stand for?A &amp; B stand for a type of protein found on the surface of RBC and i stands for the lack of this protein.</p></li><li><p>Multiple Effects of Single GenesPleiotropy.The expression of a single gene can influence two or more traits.Sickle Cell Anemia.What do you notice about the physical effects of having sickle cell anemia?*Refer to the next slide</p></li><li><p>Fig. 11.12, p. 183HbA = Normal Red Blood Cells HbS = Sickle Cell Red Blood CellsTo develop the full effects of Sickle Cell Anemia you need to be Homozygous for this trait.</p></li><li><p>Interactions Between Gene PairsEpistasisFur color in mammalsMelanin production </p><p>Albinism Comb shape in chickens (see the example in the next slides)</p><p>(When 1 gene pair influences other gene pairs with their combined activities producing some effect on phenotype)(Melanin produces fur color)(influenced by an enzyme produced from the alleles from another gene)(the absence of melanin)</p></li><li><p>Fig. 11.15, p. 185WALNUT COMB9/16 walnut(RRPP, RRPp, RrPP, or RrPp)ROSE COMB3/16 rose(RRpp or Rrpp)PEA COMB3/16 pea(rrPP or rrPp)SINGLE COMB1/16 single(rrpp)RRpp(rose comb)rrPP(pea comb)RrPp(all walnut comb)P:F2:F1:XXNOTE: Sometimes interaction between 2 gene pairs results in a phenotype that neither pair can produce alone. Comb shape in chickens can result in 4 types depending on the interactions of 2 gene pairs (R &amp; P)Epistasis Problem: Cross a Rose Comb (RRpp) chicken with a Pea (rrPP) Comb chicken. What will be the phenotype ratio of the off-spring? Cross this F1 generation. (R = Rose Comb; P = Pea Comb; RP = Walnut Comb; and rp = Single Comb)</p></li><li><p>Fig. 11.14, p. 185In some individuals the 2 genes mentioned earlier do NOT interact, causing another gene to effect coloration. At gene C, a gene at another gene locus, is responsible for the enzyme called tyrosinase, one of many enzymes responsible for the production of melanin. An individual with one of the dominant alleles (CC or Cc) can make the functional enzyme. If two recessive alleles (cc) are present, melanin production is interfered with resulting in ALBINISM.What causes this Albino snake??????</p></li><li><p>The alleles of one gene specify an enzyme for melanin production while an allele on another gene is responsible for the deposit of melanin in the hairs of the organism.B = BLACK b = BROWNE = Full deposit ee = Reduced Deposit produces a Golden color (in B or b)BlackGoldenBrownEpistasis Problem: Cross homozygous Black Lab with a Gold Lab (bbee) What would be the off-springs phenotype ratio of a cross between 2 F1 generation off-spring? List the different genotypes of each phenotype represented? (BBEE; BBEe; BbEE; BbEe)(bbEE; bbEe)(BBee; Bbee; bbee)</p></li><li><p>Less Predictable Variation in TraitsCamptodactyly (A rare genetic abnormality the affects both the shape and the movement of fingers. This can be caused by improper enzyme production.)Continuous variation (A range of small differences in the phenotypes of individuals)Eye colorHeight</p></li><li><p>Fig. 11.16, p. 186Eye Color:iris (eye color) is beneath the cornea.Color: a cumulative outcome of a number of gene productsMelanin production affects color.Dark eyes = increased amounts of melanin.Brown eyes = less melanin.Light brown/hazel = even lessGray/green/blue = very little melanin, so these wave lengths of light are reflected back to the observer.Continuous Variation:Different pairs of genes (alleles) interact to produce and deposit melanin.Eye color seems to be Continuous; fromBlack ------------- Blue(+ melanin - melanin)</p></li><li><p>Examples of Environmental Effects on PhenotypesHimalayan Rabbit &amp; Siamese CatLess melanin in warm body regions. Heat makes enzyme in melanin production pathway less activeHydrangea colorColor ranges from blue to pink, depending on acidity of soil</p></li><li><p>In ConclusionGene is unit of information about a heritable traitMendel provided indirect evidence of dominant and recessive genesF1 offspring form monohybrid crosses AA x aa -----&gt; AaCrosses from F1 result in F2 offspring with phenotypes having a 3:1 ratio</p></li><li><p>In ConclusionTheory of segregation states that genes of each pair segregate during meiosis and wind up in different gametesDihybrid crosses result in 9:3:3:1 phenotypic ratioTheory of Independent Assortment states that gene pairs independently sort out into different gametes regardless of other gene pairs of other chromosomes</p></li><li><p>In ConclusionFour factors influence gene expressionDegrees of dominanceProducts of pairs of genes may interactOne gene may effect two or more traitsEnvironment</p><p>**********************************</p></li></ul>