Introduction to Genetics - Module 1 PDF

Module 1 Introduction to bg Genetics Start Module  Module Overview pic Module 1 Introduction to Genetics Overview bg Lessons Assignment Module Overview What accounts for these similarities in parents and children? Module Ov...

Module 1 Introduction to bg Genetics Start Module  Module Overview pic Module 1 Introduction to Genetics Overview bg Lessons Assignment Module Overview What accounts for these similarities in parents and children? Module Overview What accounts for the changes in eye colour? Module Overview What accounts for the changes in eye colour? Module Overview Why can some people roll their tongues and others can’t?  Module Overview pic Module 1 Introduction to Genetics We can find the answers to these Overview questions and bg many more in Lessons understanding Genetics Assignment  Module Lessons pic Module 1 Introduction to g e m Genetics g g g What is Early Mendelism Overview Genetics? Theories bg Lessons Assignment a g Analysis of Genetic Data What is Genetics? g f What is Genetics? It is that branch of Biology concerned with Heredity and Variation (The hereditary units that are transmitted from one generation to the next (i.e. inherited) are called genes). What is Genetics? It is concerned with the transmission, expression, and evolution of genes (i.e. the molecules that bg control the function, development and the ultimate appearance of individuals). What is Genetics? > Heredity It is the transmission of genetically based characteristics from one generation to another. What is Genetics? > Heredity These characteristics (traits) are carried on genes.  Module Lessons pic Module 1 Introduction to g e m Genetics g g g What is Early Mendelism Overview Genetics? Theories bg Lessons Assignment a g Analysis of Genetic Data Early Theories on ef Hereditary Early Theories on Hereditary The existence of biological hereditary is obvious in the resemblance of children to their parents. Early Theories on Hereditary It is long known that in humans and animals, the sexual act is involved in procreation Early Theories on Hereditary It was assumed that semen was the carrier of heredity, but how this was accomplished proved difficult to establish  Historical Theories of Inheritance Preformation Epigenesis Lamarckism Pangenesis Germplasm Mendelism Jan Swammerdam Caspar F. Wolff & Jean-Baptiste Charles August Gregor & Charles Bonnet Karl Ernst von Baer Lamarck Darwin Weismann Mendel 1665 1759 1830 1868 1880 1900  Epigenesis Lamarckism Pangenesis Germplasm Mendelism Caspar F. Wolff & Jean-Baptiste August Gregor Preformation Charles Karl Ernst von Baer Lamarck Darwin Weismann Mendel Jan Swammerdam & Charles Bonnet Gametes contained a miniature individual with all the parts of the adult, and that it developed through i growth and solidification. 1665 1759 1830 1868 1880 1900  Epigenesis Lamarckism Pangenesis Germplasm Mendelism Caspar F. Wolff & Jean-Baptiste August Gregor Preformation Charles Karl Ernst von Baer Lamarck Darwin Weismann Mendel Jan Swammerdam & Charles Bonnet Homunculus The human body were already preformed in the spermatozoon. 1665 1759 1830 1868 1880 1900  Epigenesis Lamarckism Pangenesis Germplasm Mendelism Caspar F. Wolff & Jean-Baptiste August Gregor Preformation Charles Karl Ernst von Baer Lamarck Darwin Weismann Mendel Jan Swammerdam & Charles Bonnet Development was simply a matter of growth of the tiny homunculus i There were the “spermatist” and the “ovist” 1665 1759 1830 1868 1880 1900 Preformation Lamarckism Pangenesis Germplasm Mendelism Jan Swammerdam Jean-Baptiste August Gregor Epigenesis Charles & Charles Bonnet Lamarck Darwin Weismann Mendel Caspar F. Wolff & Karl Ernst von Baer Sex cells are largely homogenous bits of organic matter and contains nothing e resembling the body that will develop from them. 1665 1759 1830 1868 1880 1900 Preformation Lamarckism Pangenesis Germplasm Mendelism Jan Swammerdam Jean-Baptiste August Gregor Epigenesis Charles & Charles Bonnet Lamarck Darwin Weismann Mendel Caspar F. Wolff & Karl Ernst von Baer Organisms develop from substances present in the egg, which changes e during embryonic development 1665 1759 1809 1868 1880 1900 Preformation Lamarckism Pangenesis Germplasm Mendelism Jan Swammerdam Jean-Baptiste August Gregor Epigenesis Charles & Charles Bonnet Lamarck Darwin Weismann Mendel Caspar F. Wolff & Karl Ernst von Baer Organisms are not already present in the fertilized egg. They arise as a consequence of e profound changes in shape and form during the course of embryogenesis. 1665 1759 1809 1868 1880 1900 Preformation Lamarckism Pangenesis Germplasm Mendelism Jan Swammerdam Jean-Baptiste August Gregor Epigenesis Charles & Charles Bonnet Lamarck Darwin Weismann Mendel Caspar F. Wolff & Karl Ernst von Baer They provided a fairly accurate description of the embryonic development of a chick, e where there is a gradual change from the egg to the fetus and finally to the adult body. 1665 1759 1830 1868 1880 1900 Preformation Epigenesis Pangenesis Germplasm Mendelism Jan Swammerdam Caspar F. Wolff & August Gregor Lamarckism Charles & Charles Bonnet Karl Ernst von Baer Darwin Weismann Mendel Jean-Baptiste Lamarck Evolution was the result of acquired characteristics accumulated over many generations; and that an organism can pass on e characteristics acquired during its lifetime to its offspring 1665 1759 1830 1868 1880 1900 Preformation Epigenesis Pangenesis Germplasm Mendelism Jan Swammerdam Caspar F. Wolff & August Gregor Lamarckism Charles & Charles Bonnet Karl Ernst von Baer Darwin Weismann Mendel Jean-Baptiste Lamarck Organisms acquire traits during their life times and then pass on those traits through their sex cells to their e offspring (e.g. tattoo or scar would be inherited as tattoo or scar) 1665 1759 1830 1868 1880 1900 Preformation Epigenesis Lamarckism Germplasm Mendelism Jan Swammerdam Caspar F. Wolff & Jean-Baptiste August Gregor & Charles Bonnet Karl Ernst von Baer Lamarck Pangenesis Weismann Mendel Charles Darwin The theory was based on Lamark’s theory of acquired characteristics. Every structure which is inherited e will pass on its characteristics by contributing a small amount to the semen. 1665 1759 1830 1868 1880 1900 Preformation Epigenesis Lamarckism Germplasm Mendelism Jan Swammerdam Caspar F. Wolff & Jean-Baptiste August Gregor & Charles Bonnet Karl Ernst von Baer Lamarck Pangenesis Weismann Mendel Charles Darwin Particles (pangenes or gemmules) formed in each body part are transported through the blood e vessels to sperms/eggs and then inherited by offsprings 1665 1759 1830 1868 1880 1900 Preformation Epigenesis Lamarckism Germplasm Mendelism Jan Swammerdam Caspar F. Wolff & Jean-Baptiste August Gregor & Charles Bonnet Karl Ernst von Baer Lamarck Pangenesis Weismann Mendel Charles Darwin The similarity between parents and offspring was accounted for by postulating that, the pangenes or gemmules formed in each part of the body reflected the e characteristics of that part Supported by Aristotle and others and prevailed into the 19th Century. 1665 1759 1830 1868 1880 1900 Preformation Epigenesis Lamarckism Pangenesis Mendelism Jan Swammerdam Caspar F. Wolff & Jean-Baptiste Charles Gregor & Charles Bonnet Karl Ernst von Baer Lamarck Darwin Germplasm Mendel August Weismann The first serious challenge to the theory of pangenesis was made by August Weismann He proposed instead, the germ- e plasm theory. (Read more about this theory) 1665 1759 1830 1868 1880 1900 Preformation Epigenesis Lamarckism Pangenesis Germplasm Jan Swammerdam Caspar F. Wolff & Jean-Baptiste Charles August & Charles Bonnet Karl Ernst von Baer Lamarck Darwin Weismann Mendelism Gregor Mendel Who was Gregor Johann Mendel ? Learn More 1665 1759 1830 1868 1880 1900  Module Lessons pic Module 1 Introduction to g e m Medical Genetics g g g What is Early Mendelism Overview Genetics? Theories bg Lessons Assignment a g Analysis of Genetic Data Mendelism (Mendelian Genetics) m f  Gregor Johann Mendel Austrian Monk and Botanist Education Work Botany and Mathematics Monastic duties and groundbreaking series of inheritance Achievements The first to lay the basic laws of heredity during the mid-1800s Worked with the common pp garden pea plant, Pisum sativum Referred to as “The Father of Genetics”  Reasons in choosing the Pea Plant 1 Annual Plant Easy to cultivate with relatively short life cycle 2 Discontinuous Characteristics pp such as flower color and pea texture 3 Perfect Flowers (i.e. both female and male parts are present on one plant) and can be self-fertilized (i.e. the ovule is fertilized by pollen from the same flower.  Reasons in choosing the Pea Plant Single Trait Paid attention to a single trait at a time e.g. the shape of the seeds rather the whole plant. pp  7 Characteristics of the Pea Plant bg that are easily recognized and only occur in one of two forms: 1 Flower Colour Purple (Violet) White 2 Flower Position Axial Terminal 3 Stem Length Long Short 4 Seed Shape Round Wrinkled  7 Characteristics of the Pea Plant bg 3 that are Stem easily recognized and only occur in one of two forms: Length Long Short 4 Seed Shape Round Wrinkled 5 Seed Colour Yellow Green 6 Pod Shape Inflated Constricted 7 Pod Colour Yellow Green  Gregor Johann Mendel Austrian Monk and Botanist Education Work A Botany and Mathematics Monastic duties and groundbreaking Q series of inheritance Achievements The first to lay the basic laws of heredity during the mid-1800s Worked with the common pp garden pea plant, Pisum sativum Referred to as “The Father of Genetics”  Gregor Johann Mendel Austrian Monk and Botanist Work Approach cs Monastic duties and groundbreaking Quantitative Approach series of inheritance He counted the number c laws of of progeny of each kind d-1800s to ascertain whether Worked with the common carriers of alternate pp garden pea plant, Pisum sativum traits always appeared ther of in the same proportions  Gregor Johann Mendel Austrian Monk and Botanist Approach Experiments s and groundbreaking Quantitative Approach Mendel’s Laboratory ance He counted the number of progeny of each kind to ascertain whether e common carriers of alternate pp nt, Pisum sativum traits always appeared in the same proportions Mendel’s Laboratory Terminologies First Experiment Second Experiment  Terminologies Gene It is the basic unit of inheritance for a particular characteristic or trait Brown eye colour  Terminologies Gene A threadlike double-helical macromolecule called deoxyribonucleic acid (DNA).  Terminologies Alleles The different forms of a gene that determines alternate traits One of a number of alternate forms of the same gene responsible for Allele for brown determining contrasting eye colour characteristics Allele for blue eye colour  Terminologies Locus The position of an allele within a DNA molecule Locus for eye colour gene  Terminologies Dominance The ability of one allele to express its phenotype at the expense of an alternate allele Dominant Recessive Allele B b Allele Brown eye colour  Terminologies Recessiveness: This is where the expression of an allele is masked by an alternate allele Dominant Recessive Allele B b Allele Brown eye colour  Terminologies Recessiveness: The expression of the recessive allele can only be seen when there are two copies of that allele at a locus Recessive Recessive Allele b b Allele Blue eye colour  Terminologies Homozygous Zygotes of individual organisms carrying two units of one allele Dominant Recessive Allele B b Allele  Terminologies Heterozygous Zygotes of individual organisms carrying two different alleles (Bb or Dd) Dominant Recessive Allele B b Allele Brown eye colour  Terminologies Phenotype The visible expression of a trait or it is any measurable characteristic Bb Bb or distinctive trait possessed by an organism It is the result of gene products Trait brought to expression in a given environment Phenotype Brown eye colour  Terminologies Genotype The type of genes an organism T t possesses. Or it is all the alleles possessed by an individual Genotype B b  Terminologies Monohybrids The offspring of two parents that are homozygous for alternate alleles of a gene pair e.g. BB or bb B b  Terminologies Monohybrid Cross A cross between parents that differ at a single gene pair (usually BB x bb) B x b Bb Brown eye colour Mendel’s Laboratory Terminologies First Experiment Second Experiment First Experiment Purebred Plants which always produced offspring whose traits were exactly like that of the parent plants Purebred Tall (DD) Purebred Short (dd) First Experiment Parental Generation P1 Generation DD x Principles of Segregation dd First filial F1 Generation Hybrids Dd Dd Dd Dd First Experiment Principles of Segregation Parental Generation Alleles DD dd P1 Generation x Gametes Purity of D D d d gametes First filial F1 Generation Progeny Dd Dd Dd Dd Hybrids Dd Dd Dd Dd First Experiment Principles of Segregation The separation of paired genes (allelic pairs) from one another and are distributed to different sex cells. First Experiment Testing the Principle of Segregation Parental Generation P1 Generation DD x Principles of Segregation dd First filial F1 Generation Hybrids Dd Dd Dd Dd  First Experiment Testing the Principle of Segregation It must be noted that, the separation of the alleles could be The dwarf could detected only in the heterozygous produce only one parent (Dd) that produced two kind of gamete (d) different kinds of gametes (D) and (d) P1 Generation Backcross W h e r e F 1 ( p r o F1 Generation g e n y ) i s m a t e d o r c r o s s e d b a c Dd x k t o dd o n e o f t h e i r p a r e n Principles of Segregation t s o r w i t h a n i n d i v i d u a l t h a t h a s a p a r e n t a l g e n o t y p e Dd Dd dd dd First Experiment Recessiveness F1 Generation P1 Generation Dd x Principles of Segregation dd Recessive alleles are expressed only in homozygous (dd) individuals Dd Dd dd dd  First Experiment Recessiveness F1 Generation P1 Generation Dd x dd Carriers (Dd) are Principles of Segregation not detectable phenotypically Dd Dd dd dd  First Experiment Recessiveness Recessive alleles can be identified experimentally by crossing potential F1 Generation carriers to homozygous recessive A Testcross c r o s s o f a n o r g a n i s m w individuals (i. e. Dd x dd). i t h a n u n k n o w n g e n o t Dd x y p dd e t o a k n o w n h o m o z y g Principles of Segregation o u s r e c e s s i v e o r g a n i s m Dd Dd dd dd  First Experiment Recessiveness Testcross Recessive alleles can be identified experimentally A cross of anbyorganism crossing with potential an F1 Generation carriers to homozygous unknown genotype recessive to a known individuals (i. e. Dd homozygous x dd). organism recessive ?? x Principles of Segregation dd v e r y u s e f u l i n g e n e t i c s i n d e t e r m i n i n g t h e g e n o t dd dd y p Dd Dd e s o f i n d i v i d u a l o r g a n i s m s  First Experiment Recessiveness Testcross Recessive alleles can be identified experimentally A cross of anbyorganism crossing with potential an F1 Generation carriers to homozygous unknown genotype recessive to a known individuals (i. e. Dd homozygous x dd). organism recessive ?? x Principles of Segregation dd very useful in genetics in determining the genotypes of individual organisms (i.e. either homozygous or heterozygous of a trait).  First Experiment Testing the Principle of Segregation Backcross F1 Generation The F (progeny) is mated or P1 Generation1 crossed back to one of their Dd x parents or with an individual that dd has a parental genotype Principles of Segregation Useful in genetics studies for isolating (separating out) certain characteristics in a related group of animals or plants Dd Dd dd dd First Experiment Difference between Testcross and Backcross In testcross, a recessive homozygote is always A Testcross c r o s s o f a n o r g a n i s m w i t used as one of the h Dd a x dd n u n k n o w n g e n o t y p e t Principles of Segregation o a k n o testcross parent w n h o m o z y g o u s r e c e s s i v e o r g a n i s m This is not necessarily true in a backcross v e r y u s e f u l i n g e n e t i c s i n d e t e r m i n i n g t h e g e n o t y p e s o dd dd f i n Dd Dd d i v i d u a l o r g a n i s m s ( i. e. e First Experiment Difference between Testcross and Backcross In testcross, a recessive homozygote is always A Testcross c r o s s o f a n o r g a n i s m w i t used as one of the h DD a x dd n u n k n o w n g e n o t y p e t Principles of Segregation o a k n o testcross parent w n h o m o z y g o u s r e c e s s i v e o r g a n i s m This is not necessarily true in a backcross v e r y u s e f u l i n g e n e t i c s i n d e t e r m i n i n g t h e g e n o t y p e s o Dd Dd f i n Dd Dd d i v i d u a l o r g a n i s m s ( i. e. e Mendel’s Laboratory Terminologies First Experiment Second Experiment Second Experiment What happens when two traits (dihybrid) are considered simultaneously? Principle of Independent Assortment Round, yellow Wrinkled, green seed seed Genes or Alleles for different characters are inherited independently of one another RRYY x rryy Second Experiment P1 RRYY x rryy Gametes RY GPrinciples of Independent Assortment e n e s ry f o r d i f f e r e n t c h a r a c t e r s a r e i n h e r i t e d i n d e p e n d e n t l y o f o n e a n o t h e r F1 RrYy  Second Experiment Self Fertilization F1 What was the ratio of the four possible combinations of the two Rseed rYy characteristics? Round, yellow Wrinkled,Occur yellow in equal Gametes RY Ry rY ry frequencies Round, green Wrinkled, green F2 Using the Punnett square the following genotypes and phenotypes together with their ratios are obtained at F2  Gametes RY Ry ry rY 𝟏 𝟏 𝟏 𝟏 𝟒 𝟒 𝟒 𝟒 RRYy RrYy RrYY RY 𝟏 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔 RRYy RRyy Rryy RrYy Ry 𝟏 Gametes 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏 RrYy Rryy rryy rrYy ry 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏 RrYY RrYy rrYy rrYY rY 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔  RY Ry ry rY 𝟏 𝟏 𝟏 𝟏 𝟒 𝟒 𝟒 𝟒 RRYY RRYy RrYy RrYY RY 𝟏 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔 RRYy RRyy Rryy RrYy Ry 𝟏 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔 RrYy Rryy rryy rrYy Gametes 𝟏 ry 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏 RrYY RrYy rrYy rrYY rY 𝟒 𝟏 𝟏 𝟏 𝟏 𝟏𝟔 𝟏𝟔 𝟏𝟔 𝟏𝟔 9 :3 :3 :1  Second Experiment What was the genotypic ratio for this F1 x F1 dihybrid ratio? Mathematically, the results look like two monohybrid crosses (each expected to result in a 3:1 ratio), operating556 seeds together. (3:1)2 or (3+1)2 = (9+3+3+1) 315 108 101 32 This conforms to the law of probability called the “Product Rule” 9 3 3 1  Second Experiment Understanding of this principle is one of the key components considered in the design of many experiments in plant and animal breeding aimed at improving the quantity and quality of agricultural and animal products.  Second Experiment When a 9:3:3:1 ratios result in experiments from which parental genotypes are not known, geneticists or medical geneticists may postulate that two independent pairs of alleles are involved and that, one member of each pair behaves like dominant over its allele.  Second Experiment Dihybrid Backcross with the recessive P1 F1 P1 RrYy rryy Gametes RY Ry rY ry ry  Second Experiment Dihybrid Backcross Ratios F1 P1 RrYy rryy Gametes RY Ry rY ry ry RrYy Rryy rrYy rryy 1 : 1 : 1 : 1  Second Experiment Dihybrid Backcross Ratios Genotypic Phenotypic Phenotypes Genotypes Frequency Frequency Round, Yellow RrYy 1 1 Round, Green Rryy 1 1 Wrinkled, Yellow rrYy 1 1 Wrinkled, Green rryy 1 1 Second Experiment Trihybrid Ratios A cross between homozygous parents that differ in three gene pairs is a combination of three-pair crosses operating together as: AABBCC X aabbcc (AA X aa) (BB X bb) and (CC X cc) Second Experiment Trihybrid Ratios Example: A cross in which the seed (ovum) parent is homozygous for the genes producing a tall, yellow and round vine seeds (DDGGWW) and the pollen (sperm) parent is homozygous for dwarf, green and wrinkled vine seeds (ddggww) can best answer the question.  Second Experiment Trihybrid Backcross Example: P: DDGGWW x ddggww How many gametes can Gametes be DGWformed with thedgw F1 (DdGgWw) ? F1 DdGgWw  Second Experiment Trihybrid Ratios Example: F1 P DdGgWw x ddggww A 1:1:1:1:1:1:1:1 ratio is expected Gametes from DGWa trihybrid DGw DgW backcross Dgw to the dgw recessive parent dGW dGw dgW dgw  Second Experiment Trihybrid Backcross Ratio Example: F1 P1 DdGgWw x ddggww Gametes DGW DGw DgW Dgw dGW dGw dgW dgw dgw DGW DGw DgW Dgw dGW dGw dgW dgw dgw dgw dgw dgw dgw dgw dgw dgw 1 : 1 : 1 : 1 : 1 : 1 : 1 : 1  Frequencies Phenotypes Genotypes Genotypic Phenotypic Tall, Yellow, Round DdGgWw 1 1 Tall, Yellow, Wrinkled DdGgww 1 1 Tall, Green, Round DdggWw 1 1 Tall, Green, Wrinkled Ddggww 1 1 Dwarf, Yellow, Round, ddGgWw 1 1 Dwarf, Yellow, Wrinkled ddGgww 1 1 Dwarf, Green, Round ddggWw 1 1 Dwarf, Green, Wrinkled ddggww 1 1 Second Experiment Trihybrid Ratios How do we solve a two trihybrid F1 cross using the Punnet square? A less tedious method called the Forked-Line or Branching F1 Method is used F1 DdGgWw x DdGg Ww Second Experiment Trihybrid Ratios Forked-Line Method Procedure: 1 Assume each of the three characters is acting separately F1 F1 DdGg Ww DdGg Ww Second Experiment Trihybrid Ratios Forked-Line Method Procedure: 2 Cross the genotypes of each character separately like in monohybrid cross If one member of each pair is dominant, a 3:1 phenotypic ratio would be predicted F1 F1 from each monohybrid cross DdGg Ww DdGg Ww Dd x Dd Gg x Gg Ww x Ww Second Experiment Trihybrid Ratios Forked-Line Method Procedure: 3 Since the three pairs are independent, each monohybrid segregant may occur with any combination possible from each pair of alleles F1 F1 DdGg Ww DdGg Ww Dd x Dd Gg x Gg Ww x Ww  Procedure: 4 The combinations can therefore be systematically arranged together 3 round = 27 tall, yellow, round 3 yellow 1 wrinkled = 9 tall, yellow, wrinkled 3 tall 3 round = 9 tall, green, round 1 green 1 wrinkled = 3 tall, green, wrinkled 3 round = 9 dwarf, yellow, round 3 yellow 1 wrinkled = 3 tall, yellow, wrinkled 1 dwarf 3 round = 3 dwarf, green, round 1 green 1 wrinkled = 1 dwarf, green, wrinkled Second Experiment Dihybrid Ratios Forked-Line Method The same forked-line system may be employed to represent and combine genotypes expected from monohybrid crosses For each monohybrid cross in the system, a genotypic ratio of 1:2:1 may be predicted  Second Experiment Dihybrid Ratios Forked-Line Method P1 GGWW x ggww F1 GgWw x GgWw Gg x Gg Ww x Ww Genotypes GG 2Gg gg WW 2Ww ww  Second Experiment Trihybrid Ratios Forked-Line Method WW 1GGWW Genotypes GG 2Ww 2GGWw ww 1GGww WW 1GgWW 2Gg 2Ww 4GgWw ww 2Ggww WW 1ggWW gg 2Ww 2ggWw ww 1ggww Second Experiment Trihybrid Ratios Exercise Using the forked-line method, diagram a cross of DdGgWw x DdGgWw Show the phenotypes, genotypes, genotypic frequency as well as the phenotypic frequency. Assume that one member of each pair is dominant. Second Experiment Trihybrid Ratios Exercise Hint 1 The number of gametes, genotypes, and phenotypes expected from different numbers of heterozygous pairs of genes can be calculated without going through the Punnet square or the Forked-line. 2 The number of kinds of gametes is a multiple of 2, i.e. 2n 3 The number of F2 genotypes is a multiple of 3, i.e. 3n 1 The number of gametes, genotypes, and Second Experiment phenotypes expected from different numbers of heterozygous pairs of genes can be Trihybrid Ratios Exercise Hint calculated without going through the Punnet square or the Forked-line. 2 The number of kinds of gametes is a multiple of 2, i.e. 2n 3 The number of F2 genotypes is a multiple of 3, i.e. 3n 4 The number of phenotype is 2n when dominance is present  is present Trihybrid Ratios Exercise Hint 5 Relationships among Pairs of Independent alleles, Gametes, F2 Genotypes, and F2 Phenotypes when dominance is present. Number of Number of Number of F2 Number of F2 Heterozygous kinds Genotypes Phenotypes Pairs of Gametes 1 2 3 2 2 4 9 4 3 8 27 8 4 16 81 16 n 2n 3n 2n Mendel’s Laboratory Terminologies First Experiment Second Experiment Summary Summary Mendel’s Laws of Genetics (Most Popular) 1 Mendel’s law of Segregation 2 Mendel’s law of Independent Assortment 3 Mendel’s law of Dominance Assignment  Assignments pic Module 1 Assignment g 1 Assignment g 2 Introduction to Medical Genetics Overviewbg Lessons Assignment  Assignments pic Module 1 Assignment 1 Introduction to Medical Genetics 1 How many different gametes, F2 phenotypes and F2 genotypes can potentially be produced Overviewbg from individuals of the following genotypes? g Lessons i. AaBb Assignment ii. AaBB iii. AABbccDdEE  Assignments pic Module 1 Assignment 1 Introduction to Medical Genetics 2 A pure strain of Mendel’s peas, dominant for all seven of his independently assorting genes, was testcrossed. Overviewbg g Lessons a) How many different kinds of gametes could each of the parents produce? Assignment b) How many different gametes could the F1 produce?  Assignments pic Module 1 Assignment 1 Introduction to Medical Genetics 2 c) If the F1 was testcrossed, how many phenotypes would be expected in the Overview offspring and in what proportion? bg g Lessons d) How many genotypes would be expected in Assignment the F2?  Assignments pic Module 1 Assignment g 1 Assignment g 2 Introduction to Medical Genetics Submission date: ?/02/2020 Overview Answers bg Lessons Assignment  Module Lessons pic Module 1 Introduction to g e m Medical Genetics g g g l What is Early Mendelism Overview Genetics? Theories bg Lessons Assignment a g Analysis of Genetic Data Analysis of Genetic f a Data Probability and the Chi-Square Test Probability and Genetic Events Probability Theory Number of defined outcome(s) Probability of = occurrence (P) Total number of possible outcomes Probability and Genetic Events Probability Theory Example The probability of getting a head from a toss of a coin is 1/2 Probability and Genetic Events Probability Theory Basic Terms 1 Sample Space The set of all possible outcomes of an {Head, tail} experiment or random trial {1,2,3,4,5,6} Probability and Genetic Events Probability Theory Basic Terms 2 Event Any subset of the sample space a Ordered Event b Unordered Event Head Tail Tail Tail Probability and Genetic Events Probability of Multiple Events 1 The Rule of Independent Events 2 The Product Rule 3 The Sum Rule 4 Binomial Expansion/Distribution Probability and Genetic Events Probability of Multiple Events 1 The Rule of Independent Events The occurrence of past events have no influence on that of future events 2 The Product Rule 3 The Sum Rule 4 Binomial Expansion/Distribution Probability and Genetic Events Probability of Multiple Events 1 The Rule of Independent Events 2 The Product Rule The probability of independent events occurring together is equal to the product of their individual probabilities 3 The Sum Rule 4 Binomial Expansion/Distribution Probability and Genetic Events Probability of Multiple Events 1 The Rule of Independent Events Independence 2 The Product Rule E.g. Means that one event occurring has no if the p(A) = effect on the probability of the other 0.7, then, p(AA) = 0.7 X 0.7 = 0.49event occurring 3 The Sum Rule 4 Binomial Expansion/Distribution Probability and Genetic Events Probability of Multiple Events Questions 1 The Rule of Independent Events What is the probability of a couple 1 2 The Product Rule having 5 boys in a row? E.g. 2 What is the probability of tossing a coin if the p(A) = 0.7, then, twice and getting one head and one tail? p(AA) = 0.7 X 0.7 = 0.49 3If 2 coins are tossed, what is the chance 3 that the toss will yield 2 unmatched sides? The Sum Rule 4 Binomial Expansion/Distribution Probability and Genetic Events Probability of Multiple Events 1 The Rule of Independent Events 2 The Product Rule 3 The Sum Rule The probability of either of 2 or more independent events occurring is equal to the sum of their individual probabilities 4 Binomial Expansion/Distribution Probability 2 and Rule The Product Genetic Events Probability 3 of Multiple Events Independence 3 The Sum Rule E.g. What is the probability of a couple having either a boy or a girl? 4 Binomial Expansion/Distribution Probability 2 and Rule The Product Genetic Events Probability 3 of Multiple Events Independence 3 The Sum Rule 4 Binomial Expansion/Distribution The probability of occurrence of some arrangement of two mutually exclusive trials, where the final order is not specified, is defined by the binomial theorem: P = (n!/s!t!)(psqt) Probability 2 and Rule The Product Genetic Events Probability 3 of Multiple Events Independence 3 The Sum Rule 4 Binomial Expansion/Distribution In probability theory, events E1, E2,..., En are said to P = be (n!/s!t!)(p mutuallysqt) exclusive if the occurrence of any one of them automatically implies the non-occurrence n = number of theof trials remaining n − 1 events. Therefore, two p = probability mutuallyofexclusive an eventevents occurring on any cannot bothgiven occurtrial q = probability of the event not occurring s = number of times an event occurs t = number of times an opposite event occurs Probability 3 and Genetic Events Independence Probability 4 The Sumof Multiple Events Rule 4 Binomial Expansion/Distribution Example: A would be couple plan to have five children when they marry. Determine the probability of the couple having 3 girls and 2 boys. Probability 3 and Genetic Events Independence Probability 4 The Sumof Multiple Events Rule 4 Binomial Expansion/Distribution Solution P = (n!/s!t!)(psqt) n=5 s=3 t=2 p = 1/2 q = 1/2 Probability 3 and Genetic Events Independence Probability 4 The Sumof Multiple Events Rule 4 Binomial Expansion/Distribution Solution P = (5!/3!2!)(1/2)3(1/2)2 P = 10(1/2)3(1/2)2 P = 10/32 Probability 3 and Genetic Events Independence Probability of Multiple Events 4 Binomial Expansion/Distribution Example: If four babies are born at a given hospital on the same day: y a) What is chance that two will be boys and two girls? b) What is the chance that all four will be girls? Probability 3 and Genetic Events Independence Probability of Multiple Events 4 Binomial Expansion/Distribution x Example: A man and his wife who are both heterozygous for albinism plan to have four children. Use the information to answer the following questions. a) What is the probability that any given child will be normal? Probability 3 and hisGenetic Independence A man and Events wife who are both heterozygous for albinism plan to Probability of Multiple Events have four children. Use the 5 information tox answer the Binomial Expansion/Distribution following questions. Example: a) What is the probability that any given child will be normal? b) What is the probability that all of them would be normal? c) What is the probability that all of them are normal except the 2nd child?  information to answer the Probability 3 followingand Independence Genetic Events questions. Probability a) Whatof Multiple is the Events probability that any given child will be normal? 5 Binomial Expansion/Distribution x Example: b) What is the probability that all of them would be normal? c) What is the probability that all of them are normal except the 2nd child? d) What is the probability of having an albino child among the four children? Evaluating Genetic Data: Chi-Square Analysis The Chi-Square (χ2) Test Mendel’s 3:1 monohybrid and 9:3:3:1 dihybrid ratios are hypothetical predictions based on the following assumptions: 1 Dominance/Recessiveness 2 Segregation 3 Independent assortment 4 Random fertilization Evaluating Genetic Data: Chi-Square Analysis The Chi-Square (χ2) Test Mendel’s 3:1 monohybrid and 9:3:3:1 dihybrid ratios are hypothetical predictions based on the following assumptions: 1 Dominance/Recessiveness 2 Segregation can be affected by chance 3 Independent assortment and thus influenced by normal deviation 4 Random fertilization (Chance Deviation) Evaluating Genetic Data: Chi-Square Analysis The Chi-Square (χ2) Test 1 Dominance/Recessiveness 2 Segregation Chance Deviation 1 Can alter observed 3 Independent assortment Mendelian ratios 4 Random fertilization 2 Affected by sample size The greater the sample size the lesser the possibility of chance deviation occurring. The reverse is also true. Evaluating Genetic Data: Chi-Square Analysis Chi-Square (χ2) Distribution 1 It allows one to determine whether or not a deviation from expected Mendelian ratio can be attributed solely to chance 2 It also compares observed distribution to expected distribution (based on genetic hypotheses) and mathematically assesses whether or not the calculated χ2 value is due to chance or a real difference between the two distributions 3 It is dependent upon the sample size Evaluating Genetic Data: Chi-Square Analysis Chi-Square (χ2) Distribution 1 It allows one to determine whether or not a deviation from expected Mendelian ratio can be attributed solely to chance 2 It also compares observed distribution to expected distribution (based on genetic hypotheses) and mathematically assesses whether or not the calculated χ2 value is due to chance or a real difference between the two distributions 3 It is dependent upon the sample size Evaluating Genetic Data: Chi-Square Analysis Chi-Square (χ2) Distribution 1 It allows one to determine whether or not a deviation from expected Mendelian ratio can be attributed solely to chance 2 It also compares observed distribution to expected distribution (based on genetic hypotheses) and mathematically assesses whether or not the calculated χ2 value is due to chance or a real difference between the two distributions 3 It is dependent upon the sample size Evaluating Genetic Data: Chi-Square Analysis Calculation of Chi-Square Statistic The observed value for a given category 2 O −E χ2 = ∑ E The expected value for that category Evaluating Genetic Data: Chi-Square Analysis Calculation of Chi-Square Statistic Since (o-e) in each case is the deviation, 2 then, 𝐎 −𝐄 χ2 = ∑ E Evaluating Genetic Data: Chi-Square Analysis Calculation of Chi-Square Statistic The equation can be reduced to: χ2 = ∑d2/e Evaluating Genetic Data: Chi-Square Analysis Problem Solving Mary, a medical genetics student and a would-be graduate food technologist decided to test the 3:1 Mendelian ratio. She obtained χ2 = ∑d1000 2/eseeds in the following y proportions: Tall: 740 Dwarf: 260 Calculate the p-value and also infer if her results closely fit the 3:1 ratio. Evaluating Genetic Data: Chi-Square Analysis Step 1: Chi-Square Analysis a Hypothetical Monohybrid Cross Expected Observed Expected Deviation Deviation2 Deviation2 (d2) Ratio (o) (e) (o-e) (d2) 𝐄𝐱𝐩𝐞𝐜𝐭𝐞𝐝 (𝐞) 3 χ2 = ∑d2/e 100 = 0.13 3 740 (1000) = 750 740 – 750 =-10 (+10) 2 = 100 4 4 750 1 (-10) 2 = 100 100 = 0.410 1 260 (1000) = 250 260 -250 = 10 4 4 250 Total = 1000