1 Mendelelian Genetics copyright cmassengale. 2 Gregor Johann Mendel  Studied the inheritance of traits in pea plants  Developed the laws of inheritance

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<ul><li> Slide 1 </li> <li> 1 Mendelelian Genetics copyright cmassengale </li> <li> Slide 2 </li> <li> 2 Gregor Johann Mendel Studied the inheritance of traits in pea plants Developed the laws of inheritance Mendel's work was not recognized until the turn of the 20th century copyright cmassengale </li> <li> Slide 3 </li> <li> 3 Gregor Johann Mendel He found that the plants' offspring retained traits of the parents Called the Father of Genetics" copyright cmassengale </li> <li> Slide 4 </li> <li> 4 Genetic Terminology Gene a segment of DNA that is located in a chromosome &amp; codes for a specific heredity trait Trait - any characteristic that can be passed from parent to offspring Heredity - passing of traits from parent to offspring Genetics - study of heredity copyright cmassengale </li> <li> Slide 5 </li> <li> 5 Types of Genetic Crosses Cross mating of two individuals Gamete male and female sex cells (egg &amp; sperm) Fertilization the union of male and female gametes to form a zygote. Monohybrid cross - cross involving a single trait e.g. flower color Dihybrid cross - cross involving two traits e.g. flower color &amp; plant height copyright cmassengale </li> <li> Slide 6 </li> <li> 6 Punnett Square Used to help solve genetics problems copyright cmassengale </li> <li> Slide 7 </li> <li> 7 </li> <li> Slide 8 </li> <li> 8 Designer Genes Alleles - two forms of a gene Ex. on chromosomes that code for ht. there would be 2 alleles, short &amp; tall) Dominant - visible, observable trait; stronger of two genes expressed in the hybrid and masks the recessive. represented by a capital letter (R) Recessive hidden trait; gene that shows up less often in a cross; represented by a lowercase letter (r) copyright cmassengale </li> <li> Slide 9 </li> <li> 9 More Terminology Genotype - gene combination for a trait; genetic make up of an organism (e.g. RR, Rr, rr) Phenotype - the physical feature or visible traits of an organism (e.g. red, white) (e.g. red, white) copyright cmassengale </li> <li> Slide 10 </li> <li> 10 Genotypes Homozygous genotype both alleles are identical for a specific trait; 2 dominant or 2 recessive genes; (e.g. RR or rr); also called pure (e.g. RR or rr); also called pure Heterozygous genotype having 2 different alleles for a given 1 dominant &amp; 1 recessive allele (e.g. Rr); also called hybrid (e.g. Rr); also called hybrid copyright cmassengale </li> <li> Slide 11 </li> <li> Mendels Pea Plant Experiments copyright cmassengale11 Mendel crossed 2 plants with different characters, or forms, for the same trait. Ex. 1 tall &amp; 1 short *The plants that grew were hybrid. Hybrid are the offspring of crosses between parents with different traits. </li> <li> Slide 12 </li> <li> 12 Why peas, Pisum sativum? Can be grown in a small area Produce lots of offspring Produce pure plants when allowed to self-pollinate several generations Can be artificially cross-pollinated copyright cmassengale </li> <li> Slide 13 </li> <li> 13 How Mendel Began Mendel produced pure strains by allowing the plants to self- pollinate for several generations copyright cmassengale </li> <li> Slide 14 </li> <li> 14 Eight Pea Plant Traits Seed shape --- Round (R) or Wrinkled (r) Seed Color ---- Yellow (Y) or Green ( y ) Pod Shape --- Smooth (S) or wrinkled ( s ) Pod Color --- Green (G) or Yellow (g) Seed Coat Color ---Gray (G) or White (g) Flower position---Axial (A) or Terminal (a) Plant Height --- Tall (T) or Short (t) Flower color --- Purple (P) or white ( p ) copyright cmassengale </li> <li> Slide 15 </li> <li> Experiment I Concluded: *Each trait is based on two genes, one from the mother and the other from the father *The hybrid plants looked like only 1 parent and the character of the other parent seemed to disappear. *Each trait is controlled by 1 gene. Alleles- controls the different forms of a gene. Genes- chemical factors that determine traits. Phenotype is based on Genotype copyright cmassengale15 </li> <li> Slide 16 </li> <li> 16 Law of Dominance *States that some alleles are dominant &amp; others are recessive. *Whenever a living thing inherits a dominant allele, that trait is visible. *All the offspring will be heterozygous and express only the dominant trait. RR x rr yields all Rr (round seeds) copyright cmassengale </li> <li> Slide 17 </li> <li> 17 Law of Dominance copyright cmassengale </li> <li> Slide 18 </li> <li> 18 Law of Segregation During the formation of gametes (eggs or sperm), the two alleles responsible for a trait separate from each other. Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring Alleles for a trait are then "recombined" at fertilization, producing the genotype for the traits of the offspring. copyright cmassengale </li> <li> Slide 19 </li> <li> Experiment II: Law of Segregation Mendel crossed a tall plant (dominant) with a short plant (recessive), the F1 plant inherited an allele for tallness from the tall parent &amp; an allele for shortness from the short parent. Pg. 265 Mendel allowed his hybrid plants to self-pollinate. Some showed recessive traits, the recessive traits did not disappear. Earlier, the dominant masked the recessive, so it was not visible. Alleles for the same trait can be separated. copyright cmassengale19 </li> <li> Slide 20 </li> <li> Law of Segregation Segregation When sex cells, or gametes, are formed. Each gamete carries only 1 copy of each gene. Therefore, each F1 plant produces 2 types of gametes (some with an allele for tallness &amp; some with an allele for shortness). Ex. T, t, T, t = TT, Tt, Tt, tt copyright cmassengale20 </li> <li> Slide 21 </li> <li> 21 Applying the Law of Segregation copyright cmassengale </li> <li> Slide 22 </li> <li> 22 Probability the likelihood that a particular event will occur. Ex. Flipping a coin. The probability that it will land on tails is . </li> <li> Slide 23 </li> <li> 23 Law of Independent Assortment Alleles for different traits are distributed to sex cells (&amp; offspring) independently of one another. This helps account for genetic variations. This law can be illustrated using dihybrid crosses. Ex Pea shape &amp; pea color copyright cmassengale </li> <li> Slide 24 </li> <li> 24 Generation Gap Parental P 1 Generation = the parental generation in a breeding experiment. F 1 generation = the first-generation offspring in a breeding experiment. (1st filial generation) From breeding individuals from the P 1 generation F 2 generation = the second-generation offspring in a breeding experiment. (2nd filial generation) From breeding individuals from the F 1 generation From breeding individuals from the F 1 generation copyright cmassengale </li> <li> Slide 25 </li> <li> 25 Following the Generations Cross 2 Pure Plants TT x tt Results in all Hybrids Tt Cross 2 Hybrids get 3 Tall &amp; 1 Short TT, Tt, tt copyright cmassengale </li> <li> Slide 26 </li> <li> A Punnett Square shows: copyright cmassengale26 *All the possible results of a genetic cross. *The genotypes of the offspring. *The alleles in the gametes of each parent. </li> <li> Slide 27 </li> <li> 27 Trait: Seed Shape Alleles: R Roundr Wrinkled Cross: Round seeds x Wrinkled seeds RR x rr P 1 Monohybrid Cross R R rr Rr Genotype:Rr Genotype: Rr PhenotypeRound Phenotype: Round Genotypic Ratio:All alike Genotypic Ratio: All alike Phenotypic Ratio: All alike copyright cmassengale </li> <li> Slide 28 </li> <li> 28 P 1 Monohybrid Cross Review Homozygous dominant x Homozygous recessive Offspring all Heterozygous (hybrids) Offspring called F 1 generation Genotypic &amp; Phenotypic ratio is ALL ALIKE copyright cmassengale </li> <li> Slide 29 </li> <li> 29 Trait: Seed Shape Alleles: R Roundr Wrinkled Cross: Round seeds x Round seeds Rr x Rr F 1 Monohybrid Cross R r rR RR rrRr Genotype:RR, Rr, rr Genotype: RR, Rr, rr PhenotypeRound &amp; wrinkled Phenotype: Round &amp; wrinkled G.Ratio:1:2:1 G.Ratio: 1:2:1 P.Ratio: 3:1 copyright cmassengale </li> <li> Slide 30 </li> <li> 30 F 1 Monohybrid Cross Review Heterozygous x heterozygous Offspring: 25% Homozygous dominant RR 50% Heterozygous Rr 25% Homozygous Recessive rr Offspring called F 2 generation Genotypic ratio is 1:2:1 Phenotypic Ratio is 3:1 copyright cmassengale </li> <li> Slide 31 </li> <li> 31 And Now the Test Cross Mendel then crossed a pure &amp; a hybrid from his F 2 generation This is known as an F 2 or test cross There are two possible testcrosses: Homozygous dominant x Hybrid Homozygous recessive x Hybrid copyright cmassengale </li> <li> Slide 32 </li> <li> 32 Trait: Seed Shape Alleles: R Roundr Wrinkled Cross: Round seeds x Round seeds RR x Rr F 2 Monohybrid Cross (1 st ) R R rR RR RrRR Rr Genotype:RR, Rr Genotype: RR, Rr PhenotypeRound Phenotype: Round Genotypic Ratio:1:1 Genotypic Ratio: 1:1 Phenotypic Ratio: All alike copyright cmassengale </li> <li> Slide 33 </li> <li> 33 Trait: Seed Shape Alleles: R Roundr Wrinkled Cross: Wrinkled seeds x Round seeds rr x Rr F 2 Monohybrid Cross (2nd) r r rR Rr rrRr rr Genotype:Rr, rr Genotype: Rr, rr PhenotypeRound &amp; Wrinkled Phenotype: Round &amp; Wrinkled G. Ratio:1:1 G. Ratio: 1:1 P.Ratio: 1:1 copyright cmassengale </li> <li> Slide 34 </li> <li> 34 F 2 Monohybrid Cross Review Homozygous x heterozygous(hybrid) Offspring: 50% Homozygous RR or rr 50% Heterozygous Rr Phenotypic Ratio is 1:1 Called Test Cross because the offspring have SAME genotype as parents copyright cmassengale </li> <li> Slide 35 </li> <li> 35 Dihybrid Cross A breeding experiment that tracks the inheritance of two traits. Mendels Law of Independent Assortment a. Each pair of alleles segregates independently during gamete formation b. Formula: 2 n (n = # of heterozygotes) copyright cmassengale </li> <li> Slide 36 </li> <li> 36 Question: How many gametes will be produced for the following allele arrangements? Remember: 2 n (n = # of heterozygotes) 1.RrYy 2.AaBbCCDd 3.MmNnOoPPQQRrssTtQq copyright cmassengale </li> <li> Slide 37 </li> <li> 37 Answer: 1. RrYy: 2 n = 2 2 = 4 gametes RY Ry rY ry 2. AaBbCCDd: 2 n = 2 3 = 8 gametes ABCD ABCd AbCD AbCd aBCD aBCd abCD abCD 3. MmNnOoPPQQRrssTtQq: 2 n = 2 6 = 64 gametes copyright cmassengale </li> <li> Slide 38 </li> <li> Experiment III *Mendel wanted to see if genes that determine 1 trait have anything to do with genes that determine another. *He followed 2 different genes as they passed from one generation to the next. *Mendel crossed true-breeding plants - round yellow peas (RRYY) with wrinkled green peas (rryy). *The F 1 offspring were all round &amp; yellow showing that both were dominant alleles. The genotype is RrYy. Pg. 270 copyright cmassengale38 </li> <li> Slide 39 </li> <li> 39 Dihybrid Cross Traits: Seed shape &amp; Seed color Alleles: Alleles: R round r wrinkled Y yellow y green RrYy x RrYy RY Ry rY ry All possible gamete combinations copyright cmassengale </li> <li> Slide 40 </li> <li> 40 Dihybrid Cross RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RYRyrYryRY Ry rY ry copyright cmassengale </li> <li> Slide 41 </li> <li> 41 Dihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 copyright cmassengale </li> <li> Slide 42 </li> <li> 42 Test Cross A mating between an individual of unknown genotype and a homozygous recessive individual. Example: bbC__ x bbcc BB = brown eyes Bb = brown eyes bb = blue eyes CC = curly hair Cc = curly hair cc = straight hair bCb___bc copyright cmassengale </li> <li> Slide 43 </li> <li> 43 Test Cross Possible results: bCb___bcbbCc CbCb___bc bbccor c copyright cmassengale </li> <li> Slide 44 </li> <li> 44 Summary of Mendels laws LAW PARENT CROSS OFFSPRING DOMINANCE TT x tt tall x short 100% Tt tall SEGREGATION Tt x Tt tall x tall 75% tall 25% short INDEPENDENT ASSORTMENT RrGg x RrGg round &amp; green x round &amp; green 9/16 round seeds &amp; green pods 3/16 round seeds &amp; yellow pods 3/16 wrinkled seeds &amp; green pods 1/16 wrinkled seeds &amp; yellow pods copyright cmassengale </li> <li> Slide 45 </li> <li> Pedigrees *Pedigrees are graphic representations of a family tree, which allows for patterns of inheritance to be seen. *Each horizontal row of circles and squares represents a generation. *People that do not show the trait but are heterozygous (Tt) for the trait are called carriers. copyright cmassengale45 </li> <li> Slide 46 </li> <li> Pedigree on mouse color copyright cmassengale46 </li> <li> Slide 47 </li> <li> Different Patterns of Dominant &amp; Recessive copyright cmassengale47 Incomplete Dominance 1 allele is not completely dominant over another. Ex. Red flower (RR) &amp; white flower (WW), F1 is a pink flower (RW). Pg. 272 Codominance both alleles contribute to the phenotype. Ex. A cross of a black chicken (BB) with a white chicken (WW) will produce all speckled offspring (BBWW); colors appear separately. </li> <li> Slide 48 </li> <li> Different Patterns of Dominant &amp; Recessive Multiple Alleles have more than 2 alleles. Ex. Coat color in rabbits. Polygenic Traits traits controlled by 2 or more genes; having many genes . Ex. Variation in human skin color. copyright cmassengale48 </li> <li> Slide 49 </li> <li> 49 Incomplete Dominance F1 hybrids in betweenphenotypes F1 hybrids have an appearance somewhat in between the phenotypes of the two parental varieties. Example:snapdragons (flower) Example: snapdragons (flower) red (RR) x white (rr) RR = red flower rr = white flower R R rr copyright cmassengale </li> <li> Slide 50 </li> <li> 50 Incomplete Dominance RrRrRrRr R Rr All Rr = pink (heterozygous pink) produces the F 1 generation r copyright cmassengale </li> <li> Slide 51 </li> <li> 51 Incomplete Dominance copyright cmassengale </li> <li> Slide 52 </li> <li> 52 Codominance Two alleles are expressed (multiple alleles) in heterozygous individuals. Example: blood type 1.type A= I A I A or I A i 2.type B= I B I B or I B i 3.type AB= I A I B 4.type O= ii copyright cmassengale </li> <li> Slide 53 </li> <li> 53 Codominance Problem Example:homozygous male Type B (I B I B ) x heterozygous female Type A (I A i) IAIBIAIB IBiIBi IAIBIAIB IBiIBi 1/2 = I A I B 1/2 = I B i IBIB IAIA i IBIB copyright cmassengale </li> <li> Slide 54 </li> <li> 54 Another Codominance Problem Example:Example: male Type O (ii) x female type AB (I A I B ) IAiIAiIBiIBi IAiIAiIBiIBi 1/2 = I A i 1/2 = I B i i IAIA IBIB i copyright cmassengale </li> <li> Slide 55 </li> <li> 55 Sex-linked Traits Traits (genes) located on the sex chromosomes Sex chromosomes are X and Y XX genotype for females XY genotype for males Many sex-linked traits carried on X chromosome copyright cmassengale </li> <li> Slide 56 </li> <li> 56 Sex-linked Traits Sex Chromosomes XX chromosome - femaleXy chromosome - male fruit fly eye color Example: Eye color in fruit flies copyright cmassengale </li> <li> Slide 57 </li> <li> 57 Sex-linked Trait Problem Example: Eye color in fruit flies (red-eyed male) x (white-eyed female) X R Y x X r X r Remember: the Y chromosome in males does not carry traits. RR...</li></ul>


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