Applying Mendels Principles What are your observations about

Applying Mendel’s Principles What are your observations about the flock of sheep?

Learning Objectives § Explain how probability can be used to predict inherited traits. § Explain how alleles segregate when more than one gene is involved. § Identify Mendel’s contributions to our understanding of genetics. Vocabulary § probability-the likelihood that a particular event will occur. § homozygous (true-breeding, purebred)-two alleles are the same for a trait. Two types: homozygous dominant (AA) or homozygous recessive (aa).

Vocabulary § heterozygous (hybrid)-two alleles are different (Aa) for a trait. § Phenotype-the outward appearance of an organism. Ex. Color, size, shape, etc. § genotype-the genetic makeup of an organism. Alleles are represented by two letters. Uppercase dominant, lowercase recessive. Ex. AA, Aa, aa. § Punnett square-a diagram used to predict the outcome of a genetic cross. § independent assortment-the principle that genes for different traits can segregate independently during the formation of gametes (meiosis).

Probability and Heredity Probability: the likelihood an event will occur. • If you flip a coin, what is the probability of either heads or tails outcome: 50% or 1/2 • What is the probability of three heads in a row? 1/2 × 1/2 = 1/8 • Each flip is an independent event.

Using Segregation to Predict Outcomes Probability of a gamete receiving a G? 50%, or 1/2 Probability of gamete receiving a g? 50%, or 1/2 Probability of green offspring is. 3/4 Probability of yellow offspring is. 1/4

Genotype and Phenotype Genotype: genetic makeup Phenotype: physical traits Two organisms may share the same phenotype but have different genotypes.

Heterozygous and Homozygous: has two identical alleles for a gene Heterozygous: has two different alleles for a gene Which are: homozygous? 1, 4 1 heterozygous? 2 3 4 2, 3

Making a Punnett Square A cross of ospreys: beak size (B, b) Possible gametes Gametes for a parent along one side Combine gamete genotypes

Making a Punnett Square: Two Factors A cross of pea plants: size (T, t) and pod color (G, g) All possible gametes All gametes for a parent along one side Combine gamete genotypes

The Two-Factor Cross: F 1

The Two-Factor Cross: F 2 Independent assortment: Genes for different traits can segregate independently during gamete formation. How many phenotypes are present in the offspring? What is the phenotypic ratio? 9: 3: 3: 1 ratio of phenotypes What is the probability of getting a homozygous recessive offspring?

Summary of Mendel’s Principles, Part I Inheritance is determined by units called genes passed from parents to offspring. , which are Where more than one form of a gene for a single trait exists, some alleles may be dominant and others recessive.

Summary Mendel’s Principles, Part II • Each adult has two copies of each gene—one from each parent. These genes segregate from each other when gametes are formed. • Alleles for different genes usually segregate independently of each other.