2Who was Gregor Mendel? “FATHER OF GENETICS” He was known as the He discovered how traits were inheritedGENETICS – study of heredityHEREDITY – the passing of traits from parents to offspringClick on picture for a 15 min video at Youtube on Mendel and intro. to genetics GOOD
3Mendel’s Peas Mendel did his study on pea plants Pea plants have many traits(tall/short, purple flowers/white flowers)Pea plants can be self-fertilized or cross-fertilized
6Types of PlantsTrue-Breeding - these plants always create plants that look like themselves when crossed. AKA: PurebredTall=Tall x Tall or Short =Short x ShortHybrids – offspring from crosses of two true-breeding plants (with different traits)Hybrid=Tall x Short
7Mendel’s ExperimentsPHe experimentally crosses different varieties to develop hybrids.He then crossed the hybrids and analyzed the results.F1F2
8Genes and AllelesMendel discovered that each trait is controlled by two factors (alleles)Genes* – factors that determines traitsSo…. Alleles are two forms of the same gene ex. B vs b*FYI--Danish botanist Wilhelm Johannsen coined the word "gene“ in 1909.
9Explaining the CrossWhen a parent makes sperm or eggs, their genes (2 factors) separate (LAW OF SEGREGATION)The GAMETES (egg or sperm) contain one allele for each trait. (let T be tall and t be short)TtTtT
10PRINCIPLE OF DOMINANCE Some traits were dominant over others.PRINCIPLE OF DOMINANCETall x Short = all tall offspring (hybrids)Tall is the dominant traitShort is recessive trait (hidden)or Tall allele is dominant to the Short allele
11The Principle of Dominance Mendel's -First LawThe Principle of DominanceIn a cross of parents that are pure for contrasting traits, only one form of the trait will appear in the next generation. Offspring that are hybrid for a trait will have only the dominant trait in the phenotype.“One trait will “hide” the other trait.”
12Mendel's Second Law The 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.
14Mendel studied the appearance of his peas but did not know about genes.PHENOTYPE - what it looks like, the organisms physical description. (tall or short)GENOTYPE - the genes an organism has, represented by letters, (TT, Tt, tt)
15 Are these offspring the F1 or F2 generation? Check for understanding1. A one-eyed purple people eater is crossed with a two eyed purple people eater. All of their offspring have two eyes. Which trait is dominant?2. If you use the letter E for this gene. What is the genotype of the offspring? Are these offspring the F1 or F2 generation?4. If you crossed the offspring with each other? How many ofthe new offspring would you expect to have two eyes?
17The Law of Independent Assortment Mendel's Third LawThe Law of Independent AssortmentMa-Ma-Ma-Ma-Mendel's Third LawThe Law of Independent Assortment Alleles for different traits are distributed to sex cells (& offspring) independently of one another.
18Vocabulary for this section Mendel, dominant, recessive, trait, gene, genetics, heredity, allele, heterozygous, homozygous, hybrid, true breeding/pure breeding, test cross, P1, G1, F1, (remember the 1’s are subscripts), Punnett square, phenotype, genotype (know ratios for phenotype/genotype), classic Mendelian ratio, gamete, zygote, law of independent assortment, law of segregationThis material is covered in ch. 6 – specifically 6.3, 6.4 and 6.5