Biology Unit 5ish Notes: Mendelian Genetics

(1) Gregor Mendel Monk Studied genetics of pea plants. He noticed that: There were some traits which showed up all of the time (dominant). There were some traits which showed up some times (recessive). These traits are passed down from parents. You can’t tell just by looking at an organism, which genes it has.

(2) Dominant + Recessive Traits Dominant Trait: These will ALWAYS SHOW UP if they are present. Representation  Capital Letters Recessive Trait: These will ONLY SHOW UP if the organism inherited 2 together. Representation  Lower Case Letters

(3) Inheriting Traits You inherit 2 alleles for every gene. Gene = Chunk of DNA. Allele = Variation that chunk can come in. “Heterozygous” = You inherited 1-Dominant and 1-Recessive allele. “Homozygous” = You inherited 2 of the same alleles. “Homozygous Dominant” = You inherited 2-Dominant alleles. “Homozygous Recessive” = You inherited 2-Recessive alleles

(4) Ways to Describe Inheritance Phenotype: Physical Description. Examples: “Homozygous Recessive, White” “Heterozygous” “Homozygous Dominant, Brown” Genotype: Genetic Description. AA Aa aa

(5) What’s With These Letters? The letters represent the alleles an organism can inherit. You should choose letters with a different Capital + Lower Case appearance: A and a B and b Bad Life Choices: S and s, X and x, C and c Actual Letters DO NOT MATTER: Heterozygous needs to be: Capital + Lower Homozygous Dominant needs to be: 2 Capital Homozygous Recessive needs to be: 2 Lower

(6) Punnett Squares Punnett Square = Tool used to make genetic predictions. They do NOT tell you with certainty how many offspring will have which traits!!! Tells you probability. “There is a ¼ or 25% chance that the offspring will….” SET-UP: 1 Parent’s genotype on the top Other Parent’s genotype on the side

(7) Example #1: You cross a Homozygous Dominant Black bunny with a Homozygous Recessive White bunny….

(8) Example #2: You cross a Homozygous Dominant Black bunny with a Heterozygous bunny…

(9) Example #3: You cross a Homozygous Recessive White bunny with a Heterozygous Black bunny…