3Genetics: the study of heredity Sexual Reproduction and GeneticsCh 11Genetics: the study of heredityHeredity: the passing of traits to the next generation. (from parent to child)Trait: a physical feature (blue eyes)
4Dominant trait: a trait that always shows, can cover the other allele. - represented by a Capital letterEX: Brown eye: BRecessive trait: a trait that only shows of both alleles are present.- represented by lower case letterEX: blue eye: b
5Codominant: both alleles are expressed (shown) . EX: Bb: Brown (B) and Blue (b) eyes are both expressed
6Homozygous: two of the same alleles for a particular trait Sexual Reproduction and GeneticsHomozygous: two of the same alleles for a particular traitex: BB or bb also called pureHomozygous:Heterozygous: two different alleles for a particular traitEx: Bb also called hybridHeterozygousGregor Mendel: the father of genetics,studies the traits of pea plants
811.1 Gregor Mendel “Father of Genetics” Developed the fundamental laws of heredity He studied science and mathematics -chose to study genetics in garden peas (Pisum sativum)as as they are easily grown and their pollination is easily controlled. He controlled pollination by manually moving pollen between plants Developed True-breeding plants by self-pollination Funfact: Mendel originally wanted to breed mice, but wasn't allowed to because it was considered scandalous
9Mendel examined varieties of peas for heritable characters and traits for his study. (stem length, pod shape, seed shape, seed color..etc) Developed hybrid plants by crossbreeding two plants of differing characteristicsTall v Short
10P generation F1 F2 Mendel offspring 2 offspring 1 parents grandkids Sexual Reproduction and GeneticsMendelP generation F1 F2offspring 1kidsoffspring 2grandkidsparents
1111.2 Mendel's Law of Segregation (MONOHYBRID CROSS) A monohybrid cross involves one (mono) character and different (hybrid) traits.The F1 seeds were all purple; the white flower trait failed to appear at all.Because the purple flower trait completely masks the white flower trait when true-breeding plants are crossed, the purple flower trait is called dominant, and the white flower trait is called recessive.
12Creating the F2 generation *Cross the F1 generation together to create F2*Ratio is always 3:1Mendel proposed that the units responsible for inheritance were discrete particles - particulate theory of inheritance
13In 1865, Mendel published his findings in a paper called Experiments on Plant Hybridization, which was mostly ignored at the time due to a number of reasons. First, Mendel was not well known in scientific community. Second, his theory ran against the popular model of blended inheritance.
14As Viewed by Modern Genetics During production of gametes, only one of the pair members for a given parent passes to the gamete. (LAW OF SEGREGATION)Mendel's units of inheritance are now called genes.Different forms of a gene are called alleles.Each allele is given a symbol:Parental Cross PP x pppurple x white
15Mendel’s Three Laws 1. Dominance & Recessiveness 2. Segregation: the two alleles for a trait separate (or segregate) during the formation of gametes 3. Independent Assortment: during gamete formation, alleles pair independently, meaning a particular allele for one character can be paired with either allele of another character
16 Two copies of same allele = homozygous. Homo means "the same" Therefore both PP and pp are considered homozygous, just one is purple and the other is white.Some purple-flowered plants could be Pp. Individuals that are purple, but had a white parent, are heterozygous: Pp. Hetero means "different".The F1 crossPp x Pp purple x purple
17Review Terms F1 vs F2 True Breeding vs Hybrid Self Pollination vs Cross PollinationHomozygous vs HeterozygousParticulate Theory vs Blending TheorySegregation
18The physical appearance of an organism is its phenotype The physical appearance of an organism is its phenotype. Purple-flowered would be a phenotype.The actual composition of the organism's alleles for a gene is its genotype: Pp is a genotype.GENOTYPEPHENOTYPE Pp purple flowers rrwrinkled seedsTTtallttshortOrganisms have many different genes some have thousands, and complex organisms have 10 times that number.
19 Okay Better (use H for hair) Short hair = SS HH Short hair = Ss Hh BY CONVENTION:The dominant trait is given a capitol letter, the lowercase of that same letter is the recessive trait. DO NOT MIX LETTERS. Pick one and stick to it.Also, some letters are better than others. Capital S looks a lot like a lowercase (s). Pick a different letter... Okay Better (use H for hair)Short hair = SS HHShort hair = Ss HhLong hair = ss hh Steps to solving genetics problemsKeyParents crossPunnett SquareGenotype and ratioPhenotype and ratio
20Punnett Square: to predict outcome of offspring Steps to solving genetics problemsKeyParents crossPunnett SquareGenotype and ratioPhenotype and ratioCross heterozygous green pea (Gg) with heterozygous green pea plant (Gg). Yellow is recessive.Key: GG: Gg: gggreen yellowP = Gg x GgG gGenotype: ¼ GG; 2/4 Gg; ¼ ggGenotype ratio: 1:2:1Phenotype: ¾ green; ¼ yellowPhenotype ratio: 3:1G GG Ggg Gg ggF1
21In dragons...Wings are a dominant trait, but some dragons are born wingless.1. If a wingless dragon is crossed with one that is heterozygous, how many of its offspring will also be wingless?2. What are the chances that two heterozygous dragons have a whelp that is wingless?
22If a wingless dragon is crossed with one that is heterozygous, how many of its offspring will also be wingless?Key: FF: Ff: ffwings winglessP = ff x Fff fGenotype: 2/4= ½ Ff; ½ ffGenotype ratio: 1:1Phenotype: ½ wing; ½ winglessPhenotype ratio: 1:1F Ff Fff ff ffF1
23What is a test cross? Key: F= winged f=wingless I can help you! Let's have offspring!Help, help! I don't know what my genotype is!!Am I Ff or FF?Key:F= wingedf=wingless
24Practice with Punnett Squares 1. A round seeded plant (RR) is crossed with a wrinkle seeded plant (rr). What are the phenotypes of the offspring?2. Two heterozygous purple flowered pea plants are crossed. What are the phenotypes of their offspring and in what proportion?3. A plant with green seeds (yy) is crossed with a heterozygous plant. What percentage of their offspring have yellow seeds?
25Why does the punnett square work? It all goes back to meiosis.. each side represents a sperm or egg. The boxes filled out simply give you the statistical chance that a certain sperm will fertilize a certain egg. Probability: The chance that an event will occur- It is a prediction, and it could be wrong.
26Mendel’s Laws of Probability Can use probability and math to solve genetic problems.Ex: If two parents are heterozygous for nostril flaring.P= Ee X EeChance of E =½Chance of e = ½Chance of EE = ½ x ½ = ¼Chance of Ee = ½ x ½ = ¼Chance of eE = ½ x ½ = ¼ Ee= ¼ + ¼ = ½Chance of ee = ½ x ½ = ¼
27fF= 1 X ½ = ½ ff=1 x ½ = 1/2 Key: FF: Ff: ff wings wingless If a wingless dragon is crossed with one that is heterozygous, how many of its offspring will also be wingless?Key: FF: Ff: ffwings winglessP = ff x Ff½ ½ ½ ½1fF= 1 X ½ = ½ff=1 x ½ = 1/2
29Incomplete DominanceTraits appear to "blend" in offspringRR x WW RW (pink)Show:Pink x RedPink x PinkWhite x White
30Figure 11.14This illustrates another style of "letters" to denote genotypesR1 and R2Coloration in RodentsBlack x White = GrayBB x WW = BW
31Sickle Cell Trait in Humans Genotypes & PhenotypesPleiotropic Effect: a single mutant gene affects two or more seemingly unrelated traits- Sickle cell shape, and resistant to malaria parasite
32Prevalence of MalariaIn tropical Africa, where malaria is common:homozygous dominant individuals die of malariahomozygous recessive individuals die of sickle cell anemiaheterozygote carriers are relatively free of bothreproductive advantagePrevalence of Sickle Cell AnemiaPleiotropic Effect: a single mutant gene affects two or more seemingly unrelated traits
34ROAN COW - What happens when you cross a white and a red cow? Roan is codominant - both alleles R and W are expressed
35What happens when two Roan Cows are Crossed? R rR RR Rrr Rr rr
36In Make believe flowers……. Incomplete DominanceKey: RR = redRr = purple (BLENDING)rr = blueCoDominanceKey: RR = redRr = red and blue (both are expressed)rr = blue
37Incomplete Dominance Key: BB= Brown Bb = Tan bb = White P = Bb x Bb Ex: A brown bird crosses with a white one and all the offspring produced are tan. If these offspring were crossed and produced 16 birds, how many would be tan?Key: BB= BrownBb = Tanbb = WhiteIncomplete DominanceP = Bb x BbB bGenotype: ¼ BB; ½ Bb; ¼ bbGenotype ratio: 1:2:1Phenotype: ¼ Brown ; ½ Tan ; ¼ WhitePhenotype ratio: 1:2:1B BB Bbb Bb bbF2If these offspring produced 16 birds how many would be expected to be tan? 8
38QOD: 1. What does INDEPENDENT ASSORTMENT mean? In your own words, describe what it means with regard to Mendelian genetics.2. Mendel would have never developed this law if he'd chosen traits located on the same chromosome. Why do you think that would have altered his results?
40Mendel's Law of Independent Assortment – Illustrated by the DIHYBRID cross law describes the outcome of dihybrid (two character) crosses, or hybrid crosses involving additional characters.A dihybrid is an individual that is a double heterozygote (e.g., with the genotype RrYy - round seed, yellow seed).What are the gametes that can be produced by this individual?
41Dihybrid Cross: RrYy x RrYy Dihybrid Cross: RrYy x RrYy cross two traits at same time: remember independent assortment
42P = TtBb x TtBb Pheno ratio: 9 : 3 : 3 : 1 Key: In pigs,T = curly tail B =brown coatt = straight tail b = white coatComplete dominance Complete dominanceP = TtBb x TtBbG TB, Tb , tB, tb X TB, Tb, tB, tbPhenotype9/16 curly tail & brown coat3/16 curly tail & white coat3/16 straight tail & brown coat1/16 straight tail & white coatGenotype:1/16 TTBB2/16 TTBb2/16 TtBB4/16 TtBb1/16 TTbb2/16 Ttbb1/16 ttBB2/16 ttBb1/16 ttbbTB, Tb , tB, tbTBTbtBtbTTBBTTBbTtBBTtBbTTbbTtbbttBBttBbttbbPheno ratio: 9 : 3 : 3 : 1
43What percentage of the offspring will be hybrid for both traits? Continued….What percentage of the offspring will be purebred dominant for both traits?1/16 or 6%What percentage of the offspring will be hybrid for both traits?4/16 or 25%Genotype:1/16 TTBB2/16 TTBb2/16 TtBB4/16 TtBb1/16 TTbb2/16 Ttbb1/16 ttBB2/16 ttBb1/16 ttbbPhenotype9/16 curly & brown3/16 curly & white3/16 straight & brown1/16 straight & whiteKey: In pigs,T = curly tail B =brown coatt = straight tail b = white coat
44All of these type of crosses will follow the same ratio AaBb x AaBb both heterozygous for both traits(two dominant traits)3 - (one dominant, one recessive)3 - (one recessive, one dominant)1 - (two recessive traits)
45P = TTbb x ttbb Pheno ratio: 0 : 1 : 0 : 0 Key: In pigs, G Tb X tb 1b. T = curly tail B =brown coatt = straight tail b = white coatComplete dominance Complete dominanceP = TTbb x ttbbG Tb X tbPhenotype100% curly tail and white coatGenotype:100% TtbbTbtbTtbbPheno ratio: 0 : 1 : 0 : 0
46P = Wwhh x WWHh Pheno ratio: 1 : 1 : 0 : 0 50% 3.Key: In Drosophila fruit fliesW = long wings H = hairless bodyw = vestigial wings h = hairy bodyComplete dominance Complete dominanceP = Wwhh x WWHhG Wh, wh X WH, WhGenotype:1/4 WWHh1/4WwHh1/4 WWhh1/4 WwhhPhenotype50% long wings and hairless body50% long wings and hairy bodyWh whWHWhWWHhWwHhWWhhWwhhPheno ratio: 1 : 1 : 0 : 0What percentage of the offspring will have long wings and hairless bodies?50%
47P = LLgg x llGG Pheno ratio: 1 : 0 : 0 : 0 Key: In pea plants 2.Key: In pea plantsL = long stems G =green podsl = short stems g = yellow podsComplete dominance Complete dominanceP = LLgg x llGGG Lg X lGLgGenotype:100% LlGgPhenotype:100% long stems and green podslGLlGgPheno ratio: 1 : 0 : 0 : 0
48How many off the offspring will be short haired and red eyed? It may be faster to solve problems mathematically. This one is NOT 9:3:3:1HhBb x hhBbHow many off the offspring will be short haired and red eyed?
49Try another mathematical model.. Winged, Fire breathing dragon DdFfxWingless, Fire breathing dragon ddFfConsider the cross between a plant with round seeds, purple flowers to one with wrinkled seeds and white flowers ...RrPp x rrpp
51Multiple Alleles: more than two alleles in the population Multiple Alleles: more than two alleles in the population ex: Blood Types
52Blood TypeThere are 3 alleles that code for what type of blood you have. A, B, and O. A and B are Co-Dominant and O is recessive.Phenotype Genotype Blood Donor % of populationType A IAIA, IAiO Donate to Type A/AB %Type B IBIB, IBiO Donate to Type B/AB 10%Type AB IAIB Universal recipient/Donate to AB 4%Type O iOiO Universal Donor/ only receive O 44%
53Practice #1 P = AA x OO A A O AO AO O AO AO Genotype: Phenotype: Cross: Type A (AA) father with a type 0 mother. What are the possible blood types of the offspring?P = AA x OOA AO AO AOO AO AOGenotype:Phenotype:4/4 AO4/4 Type A
54Practice #3 A B O AO BO O AO BO BB, BO OO AB Suppose two newborn babies were accidentally mixed up in a hospital, something that rarely happens. In an effort to determine the parents of each baby, the blood types of the parents and the babies were determined.Baby 1-type B Mrs. Davisson-type B Mrs. Morgan - type OBaby 2-type O Mr. Davisson- type B Mr. Morgan - type ABA BO AO BOO AO BONameGenotypeMrs. DMr. DMrs. MMr. MBaby 1Baby 2BOOOABBB, BOOOABWhich baby belongs to Mr. & Mrs. Davisson?2. Which baby belongs to Mr. and Mrs. Morgan?Baby 2Baby 1
55blood type is located on chromosome #9 Type A, B, AB or O Chapter 9blood type is located on chromosome #9Type A, B, AB or ORH factor is a separate gene that codes for another protein. This is the positive or negative part of the blood type, on chromosome #1.
56Many Genes Have Multiple Alleles A population might have more than two alleles for a given gene.In Labrador retriever, coat color is determined by one gene with four different alleles. Five different colors result from the combinations of these alleles. (More on labradors later)Eye color is also controlled by multiple alleles
57The simulation is a bit simplified, but the idea is that MULTIPLE ALLELES control a single trait (eye color)It is likely that more than 2 alleles control eye color, this is simplified just made it simple to understand.
58Polygenic TraitsIndividual heritable characters found to be controlled by groups of several genes, called polygenes.Each allele intensifies or diminishes the phenotype.Variation is continuous or quantitative (adding up) - also called quantitative inheritanceSeed Color in wheat - aabbcc, Aabbcc, AaBbcc, AaBbCc, AABbCc, AABBCC (light, intermediate colors, dark)In humans - hair color, height, skin color
59Polygenic Inheritance Pg 197Polygenic InheritanceAABBCC x aabbcc (P)AaBbCc x AaBbCc (F1)Seven Possible Phenotypes in the F2The more “dominant” alleles for dark pigmentation (caused by melanin), the darker the skin
61Environment and Phenotype Temperature, water, food sources can have an affect on how a gene is expressed = “multifactoral”Rabbits have a gene that codes for darker pigments - this gene is more active at low temperatures. Parts of the body that are colder will develop the darker pigmentation - ears and feet
67Manx cat Lethal Genes (Not in book, added) Some genes are lethal when both alleles are present. Lethality can occur before or after birthHuntington's disease in humans is caused by a lethal allele, death occurs later in lifeOther examples: Mouse coat color (yellow), Creeper legs in chickens, Manx Cats (no tails)An example is the "creeper" allele in chickens, which causes the legs to be short and stunted.Manx cat
69Complex Inheritance and Human Heredity X-linked traits: traits on the X chromosomeColorblindnessHemophiliaMuscular DystrophyMore common in males
70Colorblindnesssex-linked recessive condition in which people can’t see certain colorsdon’t make some of the pigments in the eye that are necessary for color vision.The most common form is red-green colorblindness
71Normal color vision : 29Red green color blind : a bunch of spots!
72Normal color vision : 56Red green color blind : 56
73Normal color vision : 8Red green color blind : spots
74Hemophilia: condition that impairs the blood’s ability to clot Hemophilia: condition that impairs the blood’s ability to clot. Hemophilia is a recessive sex-linked trait.Also known as bleeders disease
76Muscular Dystrophy (MD): disease that results in progressive wasting away of skeletal muscle. Caused by a defective protein known as dystrophin
77Cross carrier female with normal male Ex:ColorblindnessKey: XX = female normal visionXXe = female carrier (normal vision)XeXe = female colorblindXY = male normal visionXeY = male colorblindCross carrier female with normal maleP = XY x X XeX YGenotype Phenotype1/4XX: female normal vision1/4 XXe : female carrier1/4 XY: male normal vision¼ XeY: male color blindXXeXX XYXXe XeYWhat % of their boys will be expected to be colorblind?50%
78Key: XX = normal female Key: XX = normal female MD HemophiliaKey: XX = normal femaleXXh = female carrierXhXh = female hemophiliacXY = male normalXhY = male hemphiliacMDKey: XX = normal femaleXXm = female carrierXmXm = female with MDXY = male normalXmY = male with MD
797. XeY male colorblind 1. XY male normal 2, XXe female carrier 9. XX or XXe10. XeY male colorblind11. XY male normal12. XeXe female colorblind
80Complex Inheritance and Human Heredity Pedigrees:A diagram that traces the inheritance of a particular trait through several generations
85Hereditary Genetic Disorders Name of DisorderType (autosomal, sex linked, dominant, recessive)Description/ SymptomsType of people group/ treatment / otherTay SacksCystic FibrosisPKUSickle Cell DiseaseNeurofibromatosisHuntington's Disease
86Tay Sachs Autosomal recessive -progressive deterioration of nerve cells and of mental and physical abilitiesYoung children begin showing signs of slowed development Severe impairment and deathstrikes 1 in 3600 births100 times greater than incidence among non-Jewsnon-functional enzyme fails to breakdown lipids in brain cellsfats collect in cells destroying their functionsymptoms begin few months after birthseizures, blindness & degeneration of muscle & mental performancechild usually dies before 5yo
87Cystic Fibrosis autosomal recessive -More common in Caucasians -Mucus in respiratory tract, difficulty breathingextreme salty sweat-Mucus may cause secondary infections
88Effect on Lungs Chloride channel transports salt through protein channel out of cellOsmosis: H2O follows Cl–Effect on Lungsnormal lungsairwayCl–Cl– channelH2Ocells lining lungscystic fibrosisCl–H2Obacteria & mucus build upthickened mucus hard to secretemucus secreting glands
89autosomal recessive Phenylketonuria (PKU) Lack enzyme for normal metabolismPhenylalanine builds up and causes brain damageNewborns are routinely testedChanges in diet lead to normal lifePhenylalanine Hydroxylase is the enzyme needed, absent in those with PKUautosomal recessive
90Sickle Cell Disease More common in Africans (African-Americans) Causes blood to be sickle shapedAffects oxygen flow to organs, causing weakness, pain, anemia, etcHeterozygotes are resistant to malariaAA = normalAa = sickle cell traitaa = sickle cell disease
91-carry high risk of tumor formation Neurofibromatosis-Autosomal dominate-carry high risk of tumor formation-Tumors form under skin and can cause skeletal deformities, blindness"The Elephant Man"Several years ago, research teams located the exact position of the NF1 gene on chromosome 17. The product of the NF1 gene is a large and complex protein called neurofibromin, which is primarily active in nervous cells as a regulator of cell division. Intensive efforts have let to the identification of the NF2 gene on chromosome 22. The NF2 gene product is a tumor-suppressor protein called merlin.
92Huntington's DiseaseHH = Huntington'sHh = Huntingtonshh = normalSymptoms appear later in life, often starting with poor muscle controlAutosomal Dominantneurodegenerative genetic disorder that affects muscle coordination and leads to cognitive decline
93Two dwarfs can have a normal child. Dd x Dd There are different types of dwarfism. Achondroplasia is caused by a dominant allele.Meet KenadieTwo dwarfs can have a normal child. Dd x DdPrimordial Dwarfism