Bio 391 CHAPTER 13 MENDELIAN GENETICS

DNA vocabulary there are 4 chromatids in a tetrad

Meiosis Process of creating 4 DIFFERENT haploid gametes

Sexual Reproduction is an Evolutionary Advantage: Mixing of Genes = More Possibilities

Beginnings Of A New Organism  Fertilization- union of the gametes Sperm – carry one set of chromosomes / genetic material from the father Egg – carry one set of chromosomes / genetic material from the mother When united, the two sets of chromosomes unite to create a genetically unique organism

ALLELES Traits are passed through generations –Traits are controlled by “Genes” Mendel called them “factors” –Genes can have multiple forms: “Alleles” = different forms of the same gene –EX: eye color alleles –Blue, green, brown… –One person is only capable of having 2 alleles DOMINANTCapital letters representing an allele = a DOMINANT allele recessive lowercase letters representing an allele = a recessive allele

Gregor Mendel: The father of genetics Manually cross pollinated the pea plants in his garden He used “true-breeding” parents –This meant that those plants always produced offspring that looked identical to the parents –Crossed a true-breeding plant with a specific trait with a true-breeding plant with a different trait Called the offspring hybrids As a result of his work, developed three genetic principles –Dominance, Segregation, Independent Assortment

Principle of Dominance When 2 True-breeding plants were crossed, only 1 trait showed in the next generation (F1) Some alleles are dominant & others are recessive Was that trait gone forever?

Law of Segregation When the F1 generations were self-pollinated, the recessive trait reappeared. For each trait an individual has two alleles (one from each parent). In turn, each individual can only pass one or the other of its alleles to its offspring.

Mendel + Meiosis

Mendelian inheritance reflects the rules of probability Rule of Multiplication “and” –Chance that two or more independent events occur simultaneously Flip a coin twice – probability of getting two heads Rule of Addition “or” –Chance of an event that can occur in two or more different ways Flip a coin – probability of getting a heads or a tails The Rules of Probability Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Probability & Punnett Squares Dominant & Recessive Homozygous & Heterozygous Genotype & Phenotype

Law of INDEPENDENT ASSORTMENT The inheritance of one gene does not influence the inheritance of another. In meiosis, the chromosomes line up randomly on the equator to be separated. If your parents are heterozygous for any traits, this leads to lots of possibilities!

Mendel discovered this through experimentation: rryy x RRYY DIHYBRID CROSS

Patterns A Het x Het dihybrid cross yields the typical genotypic ratio of: 9: 3: 3: 1