Genetics The study of heredity. Gregor Mendel Mendel was an Austrian monk. Mendel formulated two fundamental laws of heredity in the early 1860's. He.
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Gregor Mendel Mendel was an Austrian monk. Mendel formulated two fundamental laws of heredity in the early 1860's. He had studied science and mathematics (including statistics) at the University of Vienna. Mendel’s knowledge of statistics later proved valuable in his research on Heredity – the transmission of characteristics from Parent to Offspring. Mendel's work was unrecognized until 1900.
Genetics Vocabulary Monohybrid cross - cross involving a single pair of genes, one trait P – “parents” F1 – “kids” F2 – “grandkids”
Law of Segregation: Each organism contains two factors for each trait; factors segregate in the formation of gametes. When two gametes combine during fertilization, the offspring have two factors controlling a specific trait. Law of Independent Assortment: states that factors for different characteristics are distributed to gametes independently.
Genetics Vocabulary Gene - the unit of heredity; a section of DNA sequence encoding a single protein Alleles - two genes that occupy the same position on homologous chromosomes and cover the same trait Locus - a fixed location on a strand of DNA where a gene or one of its alleles is located Trait: observed expression of the gene (Physical manifestation of information)
Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short YellowGraySmoothGreenAxialTall F 1 Crosses In the first generation of each experiment, how do the characteristics of the offspring compare to the parents’ characteristics?
Genetics Vocabulary Dominant - the trait that appears in the heterozygous condition. Dominant allele capital letter Height ex: T = tall Recessive - the trait that is masked in the heterozygous condition. Recessive allele lowercase letter Height ex: t = short
Mendel’s 3rd Law Principle of Dominance 2.Some alleles are… DOMINANT recessive
Genetics Vocabulary Homozygous - having identical genes (one from each parent) for a particular characteristic. Heterozygous - having two different genes for a particular characteristic.
Genotype & Phenotype GenotypePhenotype Genetic makeup Can’t see Height ex: TT, Tt, or tt (letter code) Physical characteristic/appearance Can see Depends on genotype Height ex: tall or short Question: Can two organisms have the same phenotype but have different genotypes? Explain.
Traits exist because of 2 alleles Every trait has 2 _______ that determines its phenotype. –AA or Aa or aa AA = Homozygous Dominant Aa = Heterozygous aa = ___________ __________ It is because of this, that the recessive trait can disappear in the F1 generation.
Genetics Vocabulary Punnett squares - used to aid in predicting the probability that certain traits will be inherited by offspring Probability - is the likelihood that a specific event will occur or is the likely outcome a given event will occur from random chance
1. Determine the dominant and recessive trait Will be stated in the problem ie. Black is dominant to white in bunnies Monohybrid Crosses
2. Assign letters for the trait Dominant trait gets the capital letter Recessive traits gets the lower case letter B = black b = white
3. Determine genotype for parents White male = bb Heterozygous black female = Bb
5. Determine genotype of offspring Punnett square holds offspring genotypes B b b Genotype = letter code Bbbb Bbbb
6. Determine genotype ratio Count offspring in the Punnett square genotype ratio = 2Bb:2bb
7. Determine phenotype ratio Phenotype = what they look like Count offspring in the Punnett square phenotype ratio = 2 black:2 white *If ratio doesn’t add up to total number of boxes in the punnett square you’ve made a mistake
Practice Problems A pure-breed white flower crosses with a pure-breed purple flower. Purple is dominant to white. Show the punnett square What is the genotype of the F1 generation What is the phenotype of the F1 generation