Probability and Punnett Squares

GENETIC TERMINOLOGY OBJ define and apply the following genetic terms

New Terminology Alleles – the different forms of a gene (1 from male parent, 1 from female parent) Genes – the chemical factors that determine your traits Monohybrid Cross – crossing parent generations to test for 1 particular trait Dihybrid Cross – crossing parent generations to test for 2 particular traits

New Terminology Dominant – the form of the gene that is most often seen (indicated by a capital letter) Recessive – the form of the gene that is masked in the presence of a dominant gene, but will appear if two are present (indicated by a lower cased letter)

PUNNETT SQUARES OBJ: complete punnett squares to determine genotypic and phenotypic ratios

Genetics and Probability Probability-The likelihood that a particular event will happen is the flipping a coin – 1 chance in 2 of heads past outcomes do not affect future ones

Genetics and Probability The way that alleles segregate during meiosis is completely random Principles of probability are used to predict the outcomes of a genetic cross

Punnett Squares A diagram that shows the possible outcomes of a genetic cross

Punnett Squares Gametes of parents (top and side) The possible gene combinations for the offspring = each box of the square

Punnett Squares Each letter in the boxes - an allele used to predict and compare the genetic possibilities from a cross

What do the alleles mean? If an organism has two of the same allele for a trait (i.e. TT or tt) are called homozygous; these are the true-breed organisms for a trait

What do the alleles mean? If an organism has one of each allele for a trait (i.e. Tt) are called heterozygous; these are the hybrid organisms for a trait

What do the alleles mean? All of the tall plants have the same phenotype (physical appearance) They have different genotypes (genetic make-up, the alleles that make the physical appearance)

Monohybrid Cross

Cross Practice

Di-hybrid Cross (2 traits)

Cross Practice Cross a female that is left- handed and homozygous for tongue rolling with a male that is heterozygous right-handed and heterozygous for tongue rolling List genotypic ratio of F1 List phenotypic ratio of F1

rrTT XRrTt

New Terms Test Cross = a genetic cross used to determine the possible outcome of gametes; used to determine the genotype of an organism given the phenotype

Objectives SWBAT describe the experiments of Gregor Medel, which led to the development of modern genetics SWBAT define and apply the following genetic terms: homozygous, heterozygous, alleles, genotypes, phenotypes, probability, monohybrid/dihybrid, dominance/recessive, codominance, incomplete dominance, multiple alleles, polygenic traits, sex-linked traits, test cross, pedigree SWBAT list and explain Mendel’s laws of inheritance, noting the exceptions to the laws SWBAT complete punnett squares to determine genotypic and phenotypic ratios SWBAT discuss the characteristics and cause of some of the following genetic diseases and conditions: color blindness, hemophilia, male-pattern baldness, sickle cell anemia, albinism, cystic fibrosis, tay-sachs diease, huntingtin’s disease, dwarfism SWBAT act as a genetic counselor to determine the probability of a couple passing a genetic condition to offspring SWBAT analyze and address a bioethical issue regarding genetic engineering.