Mendel and the Gene Idea Chapter 11.1-3

Who was Gregor Mendel? The “Father of Genetics” Austrian monk with a scientific background - studied under Doppler at University of Vienna studied the heredity of pea plants first person to succeed in predicting how traits are passed from one generation to the next.

Mendel’s Experiment how did one character with 2 different traits get passed on? Needed two “true-breeding” parents (P generation) Cross-pollinated the two different strains This is called a monohybrid cross.

Mendel’s Experiment (cont’d) The first filial generation (F1) produced from the true-breeding P parents showed only the trait from one parent. Mendel allowed the F1’s to self-pollinate and the result was surprising! Both traits from the P generation resurfaced in the F2 generation, in a 3:1 ratio

Mendel’s Results From the monohybrid cross, Mendel established: rule of unit factors: each organism must have 2 factors that control its traits = “genes” and “alleles” rule of dominance: one factor (dominant) may mask the presence of another (recessive) LAW OF SEGREGATION

LAW OF SEGREGATION explains the results of a monohybrid cross: The two alleles for each trait must separate when gametes are formed. Parents pass on, at random, only one allele for each trait to each offspring. During fertilization, gametes randomly pair to produce 4 possible combinations

Mendel’s Dihybrid Cross Experiment Mendel studied how traits affect each other during a dihybrid cross: studying 2 traits at once. Tried to discover whether or not traits are inherited independently. Dependent assortment: parental pairs of traits are passed together Independent assortment: each factor is passed on independently.

LAW OF INDEPENDENT ASSORTMENT explains the results of a dihybrid cross: genes for different traits are inherited independently of each other when two dihybrid individuals mate they produce four different offspring in a 9:3:3:1 ratio if the alleles were inherited together, then only two offspring would be possible

Mendel’s Impact - Summary Also known as the “_____ of ____” Rule of _____ _____ = states that ______ are passed from parent to offspring. Rule of ________= _______ alleles mask the presence of ______ alleles. Law of ________= states ? Law of ________ ___________= states?

Beyond Mendel’s Ideas… Pea – each trait has only 1 gene; & each gene had only 2 alleles. Natural world (esp. humans) – NOT SO SIMPLE!!! There are 4 major exceptions to Mendel’s Rules…

Exceptions to Rule of Dominance Incomplete dominance: one allele is not completely dominant over another. Results in an intermediate (blend) phenotype in a heterozygous individual Codominance: both alleles are expressed equally in the phenotype. Results in a phenotype with both traits present in a heterozygote

Exceptions to Rule of Unit Factors Multiple alleles: more than 2 alleles control the expression of 1 gene. Results in extra phenotypes and genotypes. Polygenic traits: more than 1 gene controls a given trait. Results in a bell-shaped (normal) curve of phenotypes.

Chapter 12: Patterns of Heredity and Human Genetics

Objectives 12.1 Interpret a pedigree Determine human genetic disorders that are caused by inheritance of recessive alleles Predict how a human trait can be determined by a simple dominant allele

Objectives 12.2 Distinguish between incompletely dominant and codominant alleles Compare multiple allelic and polygenic inheritance Analyze the pattern of sex-linked inheritance Summarize how internal and external environments affect gene expression

Objectives 12.3 Compare codominance, multiple allelic, sex-linked, and polygenic patterns of inheritance in humans Distinguish among conditions in which extra autosomal or sex chromosomes exist

Chapter 13: Genetic Technology

Objectives 13.1 Predict the outcome of a test cross Evaluate the importance of plant and animal breeding to humans

Objectives 13.2 Summarize the steps used to engineer transgenic organisms Give examples of applications and benefits of genetic engineering