Presentation on theme: "Fundamentals of Genetics"— Presentation transcript:
1Fundamentals of Genetics Chapter 9Fundamentals of Genetics
2Section 1 Vocabulary Pretest GeneticsHeredityTraitPollinationSelf-pollinationCross-pollinationTrue-breedingP generationF1 generationF2 generationVariant of a characteristicTransfer of pollen from anther to stigmaStudy of how traits are passed from parents to offspringParent generationPassing of traits from parents to offspringFirst filial generationPollination between two different plantsSecond filial generationPollination of one flower or flowers on the same plantPure plants (for a particular trait)
3Alternate forms of a gene Allele that is expressed when only one is presentAllele that can be hiddenPair of alleles is separated during meiosisStudy of the structure and function of genes and chromosomeAlleles in a pair separate independently of one anotherDominantRecessiveLaw of SegregationLaw of Independent AssortmentMolecular GeneticsAllele
4Answer Key Genetics C Dominant L Heredity E Recessive M Trait A Law of Segregation NPollination B Law of Independent Assort. PSelf-pollination I Molecular Genetics OCross-pollination G Allele KTrue-breeding JP generation DF1 generation FF2 generation H
5GeneticsGenetics is the study of how traits are passed from parents to offspring.Heredity is the actual passing of traits from parents to offspring.Thus, Genetics is the study of heredity.A Trait is a genetically determined variant of a characteristicExample: yellow flower
6Gregor Mendel Gregor Mendel is known as the father of modern genetics. Mendel was an Austrian monk born in 1822.Experimented with garden pea plants (Pisum sativum)Presented the first paper on genetic research titled, “Experiments with Plant Hybrids” in 1866.
7Why Pea Plants?Pea plants usually self pollinate, producing pure plants.Mendel found a way to easily cross pollinate plants, allowing him to select parent plants.
8Many different traits could be studied. Easy to grow large numbers of plants, making his experiments statistically valid.Many different traits could be studied.
9Mendel studied 7 characteristics: and 14 observable traits Plant height:tall and shortFlower position:axial and terminalPod color:green and yellowPod appearance:smooth and pinchedSeed texture:round and wrinkledSeed color:yellow and greenFlower color:purple and white
10In all of Mendel’s experiments, he started with true-breeding plants Produced by allowing plants to self-pollinate for several generations so that they are pure for a traitReferred to them as the P generation (parent generation)Then cross-pollinated to get the F1 generation (first filial)These were allowed to self-pollinate to produce the F2 generation (second filial)
11Patterns began to emerge: Mendel obtained true-breeding plants for all 14 traits observed. He did hundreds of crosses and documented the results.Patterns began to emerge:Only one of the two traits appeared in the F1 generationWhat happened to the other trait?
12The second trait reappeared in the F2 generation The ratio was approximately 3 of the first trait to 1 of the second. (3:1)
14Dominant and Recessive Alleles Mendel concluded that the traits were controlled by “factors” passed down from parent plants.We now call these factors “alleles”Alleles can be either dominant or recessiveDominant alleles can mask or hide alleles for other traits. Use capital letters to represent them.Recessive alleles can be hidden by alleles for other traits. Use lower case letters to represent them.All the traits seen in the F1 generations were dominantAll the traits that reappeared in the F2 generations were recessive.
15Mendel’s LawsLaw of Segregation —states that a pair of alleles is separated during the formation of gametes.
16Law of Independent Assortment —factors for individual characteristics are not necessarily connected (unless they are carried on the same chromosome). Therefore, they separate independently of one another during the formation of gametes.
17Section 2 Vocabulary Pretest An organism’s genetic make-up (letter code)Two alleles are differentTwo alleles are sameTool for predicting the outcome of a particular crossAn organism’s appearance (word description)Likelihood that an event will occurA cross with only one characteristic1BB : 2Bb : 1bbA cross with two characteristics3 Black : 1 BrownGenotypePhenotypeHomozygousHeterozygousProbabilityMonohybrid CrossPunnett SquareGenotypic RatioPhenotypic RatioDihybrid Cross
18Both alleles for a gene are expressed in a heterozygous offspring One allele completely hides anotherPhenotype is intermediate of the parents (blending)Cross an unknown dominant with a homozygous recessiveTestcrossComplete DominanceIncomplete DominanceCodominance
19Answer Key Genotype A Phenotype E Homozygous C Heterozygous B Probability FMonohybrid Cross GPunnett Square DGenotypic Ratio HPhenotypic Ratio JDihybrid Cross ITestcross NComplete Dominance LIncomplete Dominance MCodominance K
20Phenotype and Genotype Phenotype —an organism’s appearance (word description)Phenotype for flower color: Purple or WhiteGenotype —an organism’s genetic make-up (letter code)Genotype for purple flowers: PP or PpGenotype for white flowers: pp
21Homozygous and Heterozygous Homozygous —both alleles of a pair are alike (also called pure)Homozygous white = ppHomozygous purple = PPHeterozygous —two alleles in a pair are different (also called hybrid)Heterozygous purple = Pp
22ProbabilityProbability is the likelihood that a specific event will occur.Probability is calculated by the following equation:Probability = # of times an event is expected to happen# of times an event could happenEx: Mendel grew 705 purple plants and 224 white plants. What is the probability that a purple plant will appear in a similar cross?=929Probability can be expressed as: a percent 75% a fraction ¾or a ratio 3 : 1
23T T t t Tt Tt Tt Tt Monohybrid Crosses Monohybrid Crosses —only one characteristic is trackedA tool used to predict the outcome of different types of monohybrid crosses is called a Punnett SquareNamed for Reginald PunnettExample: TT x tt (Pure tall plants x Pure short plants)TTtTtTttTtTtResult: 100% Heterozygous tall offspringGenotype = Tt Phenotype = tall
24t T t T TT Tt Tt tt Example: Tt x Tt (Hybrid tall X Hybrid tall) Genotypic Ratio: 1 TT : 2 Tt : 1 ttPhenotypic Ratio: 3 tall : 1 Short
25A testcross is performed when you are not sure if an organism showing a dominant trait is heterozygous or homozygous for the trait. To find out, it is crossed with a homozygous recessiveIf even onerecessive individualappears, thenthe unknown washeterozygous.
26Incomplete DominanceIncomplete Dominance occurs when offspring have a phenotype that is in between that of the two parents.rrRRRr
27Punnett Squares for incomplete dominance are completed in the same manner. Except that the heterozygous individuals will have the blended phenotype.Example: Pink Flower x Pink FlowerRr x RrRrResults: 25% Red flowers50% Pink flowers25% White flowersRRRRrRrrrrGenotypic Ratio: 1 RR : 2 Rr : 1 rrPhenotypic Ratio: 1 Red : 2 Pink : 1 White
28CodominanceCodominance occurs when both alleles in a pair are expressed but do not actually blend.Human Blood Type is an example of codominance.Three alleles (A,B and O) are involved in determining blood type. However, you still only inherit two (one from mom and one from dad)A and B are both dominant; O is recessiveType AB blood has one genotype: AB (both alleles are expressed and blood cells will have both A and B antigens on them)Type A blood has two possible genotypes: AA and AOType B blood has two possible genotypes: BB and BOType O blood has only one possible genotype: OO
29Dihybrid Crosses RY Ry rY ry RY RRYY RRYy RrYY RrYy Ry RRYy RRyy RrYy Dihybrid Cross --shows two traits at the same time.Example: RrYy x RrYy (heterozygous round and yellow seeds)R = round r = wrinkled Y = yellow y = greenRYRyrYryResults:9 round/yellow3 round/green3 wrinkled/yellow1 wrinkled/greenRYRRYYRRYyRrYYRrYyRyRRYyRRyyRrYyRryyrYRrYYRrYyrrYYrrYyryRrYyRryyrrYyrryy