GENETICS Section 11-1: The Work of Gregor Mendel

A. Gregor Mendel 1. Born 1822 in Czech Republic 2. Austrian monk 3. Worked in the garden at the monastery 4. Experimented with the plants in the garden:  PEAS! 5. Set foundation for Genetics

B. Flower reproduction (see Ch 24) 1. Fertilization within same plant – a.  “self-pollination” Stamen (  male) – a.  Anther: where meiosis makes pollen – b.  Filament: stalk Carpel (  female) – a.  Stigma: sticky, receptive part – b.  Style: stalk – c.  Ovary: where meiosis makes egg

C. Mendel’s Experiment 1. Mendel manually  cross pollinated the pea plants in his garden 2. He used  “true-breeding” parents – a. This meant that those plants  always produced offspring that looked  identical to the parents 3. He would cross one type of pea with another 4. He called the offspring  hybrids 5. He used seven traits in his experiments.

6. Generation Notation a.  P gen: Mendel manually fertilized one pea plant with another to produce… b.  F1 gen: the 1 st filial generation – i. He let these offspring self-pollinate to produce… c.  F2 gen: the 2 nd filial generation d. FYI… For animals: you can think of these as: – i. P  your mom & dad, F1  you, F2  your kids someday – ii. In genetic experiments, F2 does not have to be “selfed” but it often is. This should be specified

Mendel’s 7 Pea Traits Seed Shape Flower Position Seed Coat Color Seed Color Pod Color Plant Height Pod Shape Round Wrinkled Round Yellow Green Gray White Smooth Constricted Green Yellow Axial Terminal Tall Short YellowGraySmoothGreenAxialTall

D. Results of Mendel’s Experiment 1. When Mendel crossed one type by the other for each trait – a. (eg. Green x yellow) 2.  Only one of the traits showed up in the offspring. – a. Mendel called this trait  DOMINANT. 3. Was the other variety of the trait gone forever?

a. The other trait from the P generation showed up again in the  F2 generation. b. Mendel called this trait RECESSIVE. 4. Mendel called this the Principal of Dominance: some alleles are dominant & some are recessive

E. ALLELES 1. These traits were passed through generations – a. Also called  “Genes” today – b. Factors had two forms: – c. “Alleles” =  different forms of the same gene i. EX: height gene has  tall & short alleles 2. Capital letters =  DOMINANT alleles 3. lowercase letters =  recessive alleles

4. Simplest scenario… – a. For each trait an individual has two alleles:  one from each parent – b. In turn, each individual can only pass one or the other of its alleles to its offspring. 5. Mendel called this separation of alleles  SEGREGATION.

1. Phenotypes – a.  actual appearance – b. think PHoto- PHeno 2. The way the trait shows itself 3. If T is the allele for tallness and t is the allele for a dwarf plant: – a. TT-  tall plant – b. Tt-  tall plant – c. tt-  dwarf plant F. Genetic Expression

4. Genotypes a. The actual  genes (DNA) you have for a trait – a. TT-  homozygous dominant – b. Tt-  heterozygous – c. tt-  homozygous recessive b. The letters represent actual genes inherited (one from each parent)

Mendel + Meiosis

Probability & Genetics Section 11-2 Probability and Punnett Squares

A. Probability A. What is probability?  The likelihood a particular event will occur 1. Coin flipping – a. Chances of heads? – b. Chances of tails? – c. Two coins – d. Chances of two heads? Two tails? Heads & tails? 2. Rule of Multiplication – a. Past events do not affect future probabilities  INDEPENDENT!

B. Punnett Squares 1. Used to show the possible outcomes for a trait according to the traits of the parents – a. What will happen? 2. Also show the probability of the outcome – b. How often it could happen? Ee

3. Example: Ee x Ee a. Squares represent possible offspring b. Each offspring gets one gene from “dad” (from the top) c. and one gene from “Mom” (from the side) d. What % of the offspring will have free earlobes? e. What % will have attached ears? f. What % will be heterozygous for the trait? EE Ee ee E e E e Dad MomMom

C. Fast Patterns to Know Monohybrid Cross Genotype Ratio (TT : Tt : tt) Phenotype Ratio (tall : short) TT x tt Tt x TT TT x TT tt x tt Tt x Tt tT x tT Tt x tt 0:1:0 1:1:0 1:0:0 0:0:1 1:2:1 0:1:1 1:0 0:1 3:1 1:1