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What is the difference between heredity & genetics? The passing on of characteristics from parents to offspring is called heredity. The study of heredity is genetics.

GREGOR MENDEL Austrian monk who worked in the monastery gardens. One of the first to study heredity using pea plants from the gardens “Father of genetics”

He studied 7 traits- one at a time. seed seed seed pod pod flower plant shape color coat shape color arrangmnt height

MENDEL’S EXPERIMENTS P-Generation- parent generation Pollen from pure yellow seed plant crossed with egg of pure green seed plant F1 Generation- first filial generation First set of offspring from parent generation All offspring were yellow. Where did the green trait go? Developed Rule of Dominance- one trait will overpower another even if both are present. F2 Generation- second filial generation Two offspring from first generation are mated ¾ of offspring were yellow, ¼ were green How did the green trait reappear? Developed two laws: Law of Segregation Law of Independent Assortment

MENDEL’S CONCLUSIONS Rule of Unit Factors Inheritance is determined by genes passed from parent to offspring The different forms a gene can take are called alleles. You get one allele from mom & one allele from dad. EX: GENE- seed color ALLELES- for seed color are yellow & green

MENDEL’S CONCLUSIONS 2. Rule of Dominance: Some alleles are dominant and others are recessive. A. DOMINANT ALLELE Gene that is shown Represented by capital letter EX: Yellow is dominant- Y B. RECESSIVE ALLELE Gene that is hidden when a dominant allele is present Represented by a lowercase letter EX: green is recessive- y

MENDEL’S CONCLUSIONS Law of Segregation: Each pair of genes separates when gametes are formed during meiosis. Explains the disappearance of a trait in the F1 generation and its reappearance in the F2 generation.

MENDEL’S CONCLUSIONS 4. Law of Independent Assortment- The genes for different traits are inherited independently of each other b/c there is no specific way the chromosomes must line up during metaphase of meiosis

PUNNETT SQUARES Diagram that shows possible offspring that would result from two parents. Shows probability that a allele will be passed to offspring TT Tall Tt Tall Tt Tall tt short

HOMOZYGOUS When two alleles in a pair are the same. Also called purebred. Can be either: Homozygous dominant Two dominant traits YY- yellow Homozygous recessive Two recessive traits yy- green

HETEROZYGOUS Have one dominant and one recessive allele. Dominant allele is always expressed. Person is a carrier for the recessive trait. Also called hybrids EX: Yy- looks yellow but carries a green trait

Compare phenotype and genotype Genotype: gene combination of organism ex: tt, TT, Tt, GG, gg Phenotype: physical appearance of the organism ex: short, tall, green, yellow

How do you set up a Punnett Square READ the word problem. Underline the parent’s phenotype. Determine the parent’s genotype Put one parent’s genotype on the top of the Punnett and other parent’s genotype down the left side. Pull letters down into the boxes to show possible genotype combinations of offspring. Determine the offspring phenotypes and write those in the boxes. Determine genotype & phenotype percents/ratios for the offspring Each box is worth 25% or ¼ Cross a homozygous dominant tall plant with a homozygous recessive short plant Parent 1- TT Parent 2- tt Genotype Phenotype TT- 0% Tall- 100% Tt- 100% Short- 0% Tt- 0%

Types of Punnett Squares Monohybrid Crosses determining offspring’s chances of inheriting a single trait Dihybrid Crosses- determining offsprings chances of inheriting two traits together.