Presentation on theme: "Genetics: From Genetic Screening to Plant Breeding Joseph Geissler Newark Science Park High School Mrs. Paulose."— Presentation transcript:
Genetics: From Genetic Screening to Plant Breeding Joseph Geissler Newark Science Park High School Mrs. Paulose
Lesson Objectives What is genetics? – The study of heredity in an organism or population – The study of variation in an organism or population How can we investigate genetics? – Punnett Squares Mendelian Patterns of Inheritance – Complete Dominance How will you used these principles to grow tall hairy plants???
Genotype vs Phenotype Genotype- the genetic makeup of an organism – Hereditary information, the sequence of alleles i.e. RR, Rr, rr Phenotype- the expression of a genotype in the appearance or function of an organism – An physical, observable trait i.e. size, shape, color, growth
Genetic Nomenclature Allele- represents one copy of a gene; gene expression is dependent on the strength of the two alleles Monohybrid cross- investigation of one trait Dihybrid cross- investigation of two traits Dominate trait: the presence of only one allele is needed for gene expression Recessive trait: both alleles must be present for gene expression Capital letters represent a dominate trait Lower case letters represent a recessive trait
Types of Genotypes Homozygous genotype :: RR or rr – Both alleles are the same (dominate or recessive) – True-breeding organisms are homozygous for a particular trait Heterozygous genotype :: Rr – Contains mixed alleles – Observed in F1 plants of true-breeding cross
Punnett Squares of Probability R R rrrr Rr RrRr rr Rr RR Monohybrid cross of two true-breeding organisms Monohybrid cross of two heterozygous organisms 3 Dominate : 1 Recessive4 Dominate: 0 Recessive
Autosomal Dominant Disorders For inheritance, only one parents needs to be affected One dominant allele confirms phenotype Huntington’s Disease Hypercholesterolemia
Autosomal Recessive Disorders Autosomal recessive disorders can be lost and reappear several generations later For inheritance, both parents must be either affected or a carrier Two recessive alleles confirms phenotype Sickle-cell Anaemia Cystic Fibrosis
X-Linked Recessive Disorders Hemophilia Color blindness Disorder is passed to a boy from its mother, who is a carrier of the disease
Gregor Mendel’s Investigation of Pea Plant (1860s) Determined dominant and recessive traits of pea plants by performing monohybrid crosses Self-pollinating and cross pollinating techniques used to investigate individual traits
Parental Generation R R rrrr Rr Cross pollination of two true breeding plants So, what is the phenotype of F1? GenotypePhenotype RR Round-seeded plants rr Wrinkled-seeded plants F1 generation
F2 Generation R r RrRr rr Rr RR Self-fertilization cross of F1 generation plants GenotypePhenotype RRRound-seeded plant RrRound-seeded plants rrWrinkled-seeded plant Genotypic Ratio 1 RR : 2 Rr : 1 rr Phenotypic Ratio 3 Round : 1 Wrinkled
Incomplete Dominance Genotypic Ratio 1 RR : 2 Rr : 1 rr Phenotypic Ratio 1 red : 2 pink : 1 white Phenotype is an intermediate between the parents GenotypePhenotype RRRed Flower RrPink Flower rrWhite Flower
Blood Type Multiple alleles A,B, and i Phenotype (Blood type) GenotypeCarbohydrate on surface of red blood cells Antibody Response Type AI A I A or I A iA Anti-B Type BI A I A or I B iB Anti-A Type ABI AI BI AI B A and B Neither Anti-A nor Anti-B Type O i iNeither A nor B Anti-A and Anti-B
Punnett Square Activity Dominant Trait Recessive Trait Cross two true breeding plants particular for one trait (P). What are the genotypes of the F1 population? Cross two F1 plants. What are the genotypes of the F2 population? What does this tell us about genetics? Next, cross one of the parental traits with an F1 (RR vs Rr). How can these crosses give rise to true breeds?
Tall and Hairy Two advantageous traits a plant can possess it to be tall and hairy. For this experiment, you will apply your knowledge of botany and genetics to generate true-breeding plants for these traits. Thanks to Mendel, we can accurately predict the outcomes of our crosses and do not need years of experiments to do so.