Transcript Chapter 25
Chapter 11 Introduction to Genetics (no two are the same) Section Outline Section 11-1 11–1 The Work of Gregor Mendel A. Gregor Mendel’s Peas B. Genes and Dominance C. Segregation 1. The F1 Cross 2. Explaining the F1 Cross Introduction • The branch of science that is concerned with the ways in which inheritable information is transmitted to offspring is known as Genetics Introduction and Reminders – Heredity: traits (characteristics) are passed down from the parent to the offspring. – Sexual Reproduction: the fusion of sex cells • Sex cells (gametes) sperm and ova cells – Chromosomes of each gamete contain the traits of th parent (A) Gregor Mendel Do now Video: Understanding Genetics 20:24 (A) Gregor Mendel An Austrian monk who performed a series of experiments with sweet peas (1856-1868) Experimented on pea plants because he Knew: Peas Self- Pollinated They have Single parent Example of Selective (True/pure) Breeding Fertilization occurred: fusion of sperm and eggs cells Reproduced in high numbers in a short time (A) Gregor Mendel He wanted to see how these traits were inherited by the offspring plants Mendel proposed that certain traits were inherited as a result of the transmission of hereditary factor Mendel’s hereditary factors, called genes , (A) Gregor Mendel Two genes (one from each parent) called alleles determine the trait of the offspring Genes are the Chemical factors Example~~ Gene for: Flower Color ~ ~ (B) Genes and Dominance He studied Seven traits -Trait: a specific characteristics, ex Height, color, shape -Each trait had two contrasting Characteristics: Trait 1. 2. 3. 4. 5. 6. 7. . Contrasting Characteristics: flower color flower position seed color seed shape stem length pod shape pod color purple or white axial or terminal yellow or green round or wrinkled long or short inflated or constricted yellow or green “Same Gene Different Alleles” B. Genes and Dominance Mendel’s Seven F1 Crosses on Pea Plants What???? Seed Shape Seed Color Seed Coat Color Round Yellow Gray Wrinkled Green Round Yellow White Gray Pod Shape Smooth Pod Color Green Constricted Yellow Smooth Green Flower Position Axial Terminal Axial Plant Height Tall Short Tall B. Genes and Dominance His Hypothesis was something was transmitting information to the offspring Principles of Dominance Section 11-1 B. Genes and Dominance P Generation Tall Short F1 Generation Tall Tall F2 Generation Tall Tall Tall Short Principles of Dominance Section 11-1 B. Genes and Dominance P Generation F1 Generation F2 Generation 100% Tall Short Tall Tall Tall Tall Tall Short Principles of Dominance Section 11-1 B. Genes and Dominance P Generation F1 Generation F2 Generation 75% Tall Short Tall Tall Tall Tall 25% Tall Short P F1 (100% pure) F2 (75%, 25%) (B) Genes and Dominance P F1 (100% pure) F2 He studied Seven traits his F2 numbers were staggering 787 705 277 244 6000 2000 Mendel's Three Major Concepts Law of Dominance Segregation Independent Assortment Principle of Dominance 1. Principle of Dominance 1. Principle of Dominance Also referred to as Law of Dominance • States that the dominant allele will mask (cover) the recessive allele if the pair is hybrid • Tt = tall, since T is dominant for tallness • The only time that the recessive allele is shown is when its homozygous recessive • tt = short Law of Segregation 2. Principle of Segregation • States that the alleles of an allelic pair will separate and then recombine to form a new trait • Ex: Punnet square Tt T t 2. Principle of Segregation Parent 1 Separation Recombination Video: Segregation chapter 11d Parent 2 Do Now: 1. Copy the table below. 2. In the table Define the words genotype + phenotype (using your homework) 3. Match the examples below in the appropriate box: Blue eyes, tall, homozygous, hybrid, short, heterozygous Phenotype Definition Examples Genotype Do Now: Phenotype Definition the PHYSICAL appearance of the offspring due to the genotype Examples Blue eyes, tall short, Genotype genetic makeup of an organism (is it homozygous or heterozygous) homozygous, hybrid, heterozygous 2. (RVW). Principle of Segregation Parent 1 Separation Recombination Video: Segregation chapter 11d Parent 2 Section Outline 11–2 Probability and Punnett Squares Section 11-2 A.Genetics and Probability B. Punnett Squares C. Probability and Segregation D.Probabilities Predict Averages Tt X Tt Cross Section 11-2 Tt X Tt Cross Basic Terms: • Genotype- genetic makeup (is it homozygous or heterozygous) – Homozygous: a.k.a. Pure, Having the same alleles, (BB, bb) – Heterozygous: a.k.a. Hybrid, Having different alleles for a certain trait (Bb) • Phenotype- the PHYSICAL appearance of the offspring due to the genotype Homozygous • Pure • Both alleles are the same • TT = homozygous tall • tt = homozygous short Heterozygous • Also known as Hybrid • Both alleles are different • Tt = heterozygous or hybrid Homozygous Dominant x Homozygous Dominant Round Round 4 round peas Homozygous Dominant x Homozygous Recessive Round Wrinkled Heterozygous Dominant x Heterozygous Dominant Round Round Wrinkled How can we identify this pea’s genotype???? (RR or Rr) Law of Independent Assortment (III) Generations P1 (parents) TT x tt F1 (offspring) Tt F2 (grandchildren) TT, Tt, tt (III) Generations In the early 1900’s, T.H. Morgan carried out breeding experiments (crosses) with the fruit fly, Drosophila melanogaster that supported Mendel’s findings • Is tongue rolling a dominant or recessive trait??? • Is tongue rolling a dominant or recessive trait??? • 1` • TT, Tt tt Punnet Square Used to predict possible offspring Background Information 1. Genes: have alleles (found on chromosomes) 2. Capital letter = dominance Lower-case letter = recessive Ex: T = tallness which is dominant t = shortness which is recessive T = Tall t = short T T t Tt Tt t Tt Tt How many offspring are Tall? How many offspring are short? T = Tall t = short T T t Tt Tt t Tt Tt How many offspring are Tall? 4 = Tall How many offspring are short? 0 = short T = Tall t = short T t T TT Tt t Tt tt How many offspring are Tall? How many offspring are short? T = Tall t = short T t T TT Tt t Tt tt How many offspring are Tall? 3 = Tall How many offspring are short? 1 = short G = green g = yellow G G GG GG g Gg Gg G G = green g = yellow G G GG GG g Gg Gg Phenotype = green G Genotype = symbols G = green g = yellow G G GG Gg g Gg gg g Phenotypes = green and yellow Law of Independent Assortment Law of Independent Assortment Independent Assortment Dihybrid = 2 allelic pairs T= tall t = short Y= yellow seeds y= green seeds TtYy x TtYy Dihybrid Cross (Possible Gametes) TtYy x TtYy TtYy TY Ty Yt ty Dihybrid Cross (Possible gametes) TtYy x TtYy TtYy TY Ty Yt ty Dihybrid Cross (Possible Gametes) TtYy x TtYy TtYy TY Ty Yt ty Dihybrid Cross (Possible Gametes) TtYy x TtYy TtYy TY Ty Yt ty Dihybrid Cross TY TtYy x TtYy Ty Yt ty TY TTYY TTYy TtYY TtYy Ty TTYy TTyy TtYy Ttyy Yt TtYY TtYy ttYY ttYy ty ttYy ttyy TtYy Ttyy Dihybrid Cross F2 is always 9:3:3:1 TY Ty Yt TTYy TtYY TTYY TY TallYellow TallYellow TallYellow ty TtYy TallYellow TTyy TTYy Ty TallYellow Tall green TtYy Ttyy TallYellow Tall green Yt TtYY TtYy ttYY ttYy TallYellow TallYellow shortYellow shortYellow ty TtYy TallYellow Ttyy ttYy ttyy Tall green shortYellow short green 9 are Tall & yellow TY 1 Ty 2 ty Yt 3 4 TY TTYY TTYy TtYY TtYy 5 6 Ty TTYy 7 TtYy 8 Yt TtYY TtYy ty 9 TtYy 3 are tall & green TY Ty ty Yt TY 1 Ty TTyy Yt ty 3 Ttyy 2 Ttyy 3 are short & yellow TY Ty ty Yt TY Ty Yt ty 1 ttYY 3 ttYy 2 ttYy 1 is short and green TY Ty ty Yt TY Ty Yt ty 1 ttyy Black hair in guinea pigs is Dominant over brown hair. ***Prove the genotype of a unknown black haired guinea pig. B = Brown b = blue B b b b How many offspring are Brown eyed? How many offspring are blue eyed? B = Brown b = blue B b b Bb bb b Bb bb How many offspring are Brown eyed? How many offspring are blue eyed? How are the laws of Segregation and Independent Assortment Similar but very different? How are the laws of Segregation and Independent Assortment Similar but very different? Both lead to major Genetic variations from parents to offspring Chapter 27 Heredity Intermediate Inheritance Mendelian Incomplete dominance Codom inance Dominance (IV) Intermediate Inheritance Multiple Alleles (IV) Intermediate Inheritance • The hybrid offspring are phenotypically different (look different) than their homozygous parents • types: 1. 2. 3. 4. 5. 6. Incomplete Dominance Co dominance Multiple Alleles Polygenic traits Epistatic Genes, (Mask over other genes) Sex linked genes Incomplete dominance • Think pink roses • Both alleles are dominant • Blending of traits • F1 generation = pink roses. The roses will be pink due to a blending of traits Incomplete dominance Incomplete dominance Genetics: Incomplete Dominant Description: A Ball Python with heavily speckled side pastern and a nearly complete dorsal stripe that breaks up at the neck and then fades into the base of the head. This appearance is similar in color to the Cinnamon Pastel, but does not have the fading or "blushing." I have a small group of granites that I expect to produce an ebony when bred to a yellow belly. I am also excited to find out if there is a super form of the granite. Incomplete Dominance R = Red W = White W W R R How many offspring are Red? How many offspring are white? Incomplete Dominance R = Red W = White W W R RW RW R R W RW How many offspring are Red? How many offspring are white? Incomplete Dominance Co dominance • Both alleles are dominant • Mixture of the 2 traits • F1 generation = roan cattle. Cattle that is roan will have both white hairs and red hairs on it (mixture) • Red cow (RR) • White cow (WW) • Roan cow (RW) Co dominance • Both alleles are dominant • Mixture of the 2 traits • F1 generation = roan cattle. Cattle that is roan will have both white hairs and red hairs on it (mixture) • Red cow RR White cow WW Roan cow RW Co dominance • Cross a Red cow with a Roan cow Co dominance Codominance For some traits, two alleles can be codominant. That is to say, both are expressed in heterozygous individuals. An example of this is people who have an AB blood type for the ABO blood system. Type AB blood testing as both A and B Blood types are an example of Co dominance and Multiple Alleles When they are tested, these individuals actually have the characteristics of both type A and type B blood. Their phenotype is not intermediate between the two. Type AB blood testing as both A and B Co dominance • In co dominance and incomplete dominance, the F2 generation is always 1:2:1 (V) Multiple Alleles • No more than two alleles for a given trait may be present within each cell • Ex: blood types • A,B,AB, & O Blood Types I = dominant i = recessive Ex: A man with heterozygous blood type A marries a woman with blood type O. What are the possibilities of blood types for the children Blood Types A I i i i How many offspring have type O? How many offspring have type A? Blood Types A I i i A I i ii i IA i ii How many offspring have type O? How many offspring have type A? Epistatic Genes Epistatic Genes BBEE BbEE BBEe BbEe bbEE bbEe BBee Bbee bbee • Black is dominant to chocolate B or b Yellow is recessive epistatic (when present, • it blocks the expression of the black and chocolate alleles) E or e • Cross a pink rose with a white rose. • What are you geno and phenotypes? • Red: RR • White: R’R’ • Pink: R’R The Chromosome Theory of Inheritance: • By Sutton Color blindness- • If you see the number 74, then you do not have red-green color blindness. • If you see the number 21, you are color blind to some extent. A totally color-blind person will not be able to see any of the numbers. This is how a true color blind individual sees it What do you see in the four circles? • 1. Normal Color Vision: A: 29, B: 45, C: --, D: 26 • 2. Red-Green Color-Blind: A: 70, B: --, C: 5, D: -- • 3. Red Color-blind: A: 70, B: --, C: 5, D: 6 • 4. Green Color-Blind: A: 70, B: --, C: 5, D: 2 What do you see? What do you see? A person with red-green color blindness may be unable to identify the"5 or 6 What do you see? What do you see? • PROTANOPIA & DEUTERANOPIA Those with normal vision see the number thirty-five in the circle. • A person with protanopia sees only he number five. • A person with deuteranopia sees the number three. People who are partially color blind will see both numbers but one more distinctly than the other. • Color blindness– If you see the number This is how a true color blind individual sees it Sex Determination Sex determination in humans • Males are XY • Female XX • Who determines the sex of the offspring? X X X Y Sex determination in humans • Males are XY • Female XX • Who determines the sex of the offspring? DAD!!! X Y X XX XY X XX XY Gene Linkage • One human cell contains about 100,00 genes •Each cell has 46 chromosome, SO • Each chromosome has thousands of genes *****Linked genes are located on the same gene Sex linked disorders • Color blindness and Hemophilia are both recessive disorders on the “X” chromosome. • So what does this mean? Sex linked disorders X X X Y Sex determination in humans X X X Y Polygenic Traits Some traits are determined by the combined effect of more than one pair of genes. These are referred to as polygenic, or continuous, traits. An example of this is human stature. The combined size of all of the body parts from head to foot determines the height of an individual. There is an additive effect. Polygenic Traits There is an additive effect. The sizes of all of these body parts are, in turn, determined by numerous genes. Human skin, hair, and eye color are also polygenic traits because they are influenced by more than one allele at different loci. Gene Arrangement on Chromosomes: Linkage Analysis How are Genes arranged on Chromosomes? •Study by linkage analysis using genetic crosses •An allele of a gene is at a specific locus on a chromosome •Most pairs of genes obey Mendel's Law of Segregation in a dihy cross •Some allele pairs do not segregate independently Linkage: Genes that are inherited together. Three inheritance patterns are possible: 1.Non-linkage: Independent assortment of alleles. Genes on differ chromosomes, i.e. Dihybrid Cross 2.Complete linkage: Genes on a chromosome inherited as a uni (Problem Set #2-10). 3.Partial linkage: Intermediate behavior between non-linkage an linkage. From partial linkage analysis we can learn about the ord and spacing of genes on chromosomes. Homologous Chromosomes Recombine During Meiosis •Formation of recombinant genotypes or phenotypes. •Combinations of alleles not present on either parental chromoso can be created. Outline using cyberEd: Heredity Cross a Hybrid brown eyed father with a blue eyed mother!!! B = Brown b = blue How many offspring are Brown eyed? How many offspring are blue eyed? Organize the following terms Alleles, Nucleus, genes, homologous chromosome, Cell (I) Foundations of Genetics Cell nucleus homologous chromosome genes alleles