11-1 The Work of Gregor Mendel A. Genes and Dominance During sexual reproduction, sperm and egg cells join in a process called fertilization. Fertilization produces a new cell. Gregor Mendel (the father of genetics) had true- breeding pea plants that, if allowed to self- pollinate, would produce offspring identical to themselves. Cross the following traits; Pink Pp x White pp- make a Punnett square… Pea flowers are self-pollinating. Sperm cells in pollen fertilize the egg cells in the same flower

Genetic’s Vocabulary Define/Use common words or pictures Homozygous dominant Homozygous recessive Heterozygous Punnett square Phenotype Genotype Trait Hybrid Diploid Haploid Crossing over Chromosome Gene Incomplete dominance Codominance

11-1 The Work of Gregor Mendel A. Genes and Dominance How to perform a genetic cross Each original pair of plants is the P (parental) generation. The offspring are called the F1, or “first filial,” generation. The offspring of crosses between parents with different traits are called hybrids. Mendel’s F1 Crosses on Pea Plants

11-2 Probability and Punnett Squares B. Genetics and Probability Probability can be used to predict the outcomes of genetic crosses. A capital letter represents the dominant allele for tall. A lowercase letter represents the recessive allele for short. In this example, T = tall t = short Organisms that have two identical alleles for a particular trait are said to be homozygous. (TT or tt) Organisms that have two different alleles for the same trait are heterozygous. (Tt) Cross the following traits; Pink Pp x White pp- make a Punnett square… Pea flowers are self-pollinating. Sperm cells in pollen fertilize the egg cells in the same flower

Parents Brown Eye vs Green Eye B= Brown Eye– BB Bb b= green eye– bb only

11-2 Probability and Punnett Squares B. Genetics and Probability All of the tall plants have the same phenotype, or physical characteristics. The way it looks. The tall plants do not have the same genotype, or genetic makeup. The letters One third of the tall plants are TT, while two thirds of the tall plants are Tt. The plants have different genotypes (TT and Tt), but they have the same phenotype (tall). The Gametes or (sperm and Eggs get ½ the chromosomes from each parent to make a zygote.

11-2 Probability and Punnett Squares C. Probability and Segregation One fourth (1/4) of the F2 plants have two alleles for tallness (TT). 2/4 or 1/2 have one allele for tall (T), and one for short (t). One fourth (1/4) of the F2 have two alleles for short (tt). Because the allele for tallness (T) is dominant over the allele for shortness (t), 3/4 of the F2 plants should be tall. The ratio of tall plants (TT or Tt) to short (tt) plants is 3:1.

11–3 Exploring Mendelian Genetics The Punnett square predicts a 9 : 3 : 3 :1 ratio in the F2 generation. D. The Two-Factor Cross: F1   Mendel crossed true-breeding plants that produced round yellow peas (genotype RRYY) with true-breeding plants that produced wrinkled green peas (genotype rryy). The Two-Factor Cross: F2  Mendel crossed the heterozygous F1 plants (RrYy) with each other to determine if the alleles would segregate from each other in the F2 generation. RrYy × RrYy

Cross SsYy x SsYy

Genetic trait control 11.3 E. Some trait are not completely dominant, this is called Incomplete Dominance. Crossing a red snapdragon flower w/ a white snapdragon flower produces a pink snapdragon. Neither one is completely dominant. Some traits are affected by many genes, these are polygenic, this would include skin color.

F. Some traits are codominant, they both appear at the same time a red and a white cows produce a roan offspring it has red and white hair mixed. Zebras are black, white and brown