1. C HAPTER 11 O BJECTIVES 1. Explain why Mendel’s experiments are important in science. 2. Describe the following terms and how they related to genetics: gene, allele, dominant, recessive, homozygous, heterozygous, phenotype, and genotype. 3. Demonstrate the principle of segregation and independent assortment in terms of chromosomes and meiosis. 4. Solve genetic problems by using monohybrid Punnett squares. (Involves setting up problems, working out problems, and giving the phenotype/genotype ratios) 5. Explain the principle of independent assortment and analyze dihybrid crosses. 6. Explain the other patterns of dominance: Incomplete, Co- dominance, Polygenic, Multiple Alleles, Sex-linked. 7. Explain what a pedigree is and analyze a pedigree for genetic traits.

2. G REGOR M ENDEL (1822-1884) The Father of Genetics Worked on Pea Plants Contained a variety of traits Genetics : The study of heredity Heredity : Something that gets passed on from one generation to the next

3. 2. D ESCRIBE THE FOLLOWING TERMS AND HOW THEY RELATED TO GENETICS Trait : a specific characteristic that varies from one individual to another Crosses : Mating between parents Hybrid : Offspring of crosses between parents with different traits True-breed: Offspring of crosses between parents with identical traits Genes : Chemical factors that determine traits Alleles : Different forms of the gene

4. 3. S UMMARIZE THE PRINCIPLES OF DOMINANCE. Principle of Dominance : Some alleles (different forms of genes) are dominant while others are recessive Dominant : Always is the trait that is shown We show this as having a capital letter Recessive : Will only show the trait if the dominant is not present We show this as having a lowercase letter

5. Homozygous : Organisms that have two identical alleles for a particular trait Can be dominant or recessive Also known as true-breeds Example: TT or tt Heterozygous: Organisms that have two different alleles Know as hybrids Example: Tt

6. 5. A NALYZE P UNNETT SQUARES TO DETERMINE THE OUTCOME OF PARENTAL CROSSES. Phenotype : Physical characteristics (Uses Traits) Ex: Tall, Short, Purple, White Genotype : Genetic makeup (Uses the “letters”) Ex: TT, Tt, tt BIG IDEA : The number of phenotypes you have may not match the number of genotypes.

7. 9. E XPLAIN THE OTHER PATTERNS OF DOMINANCE : I NCOMPLETE, C O - DOMINANCE, P OLYGENIC, M ULTIPLE A LLELES, S EX - LINKED. Incomplete Dominance : Heterozygote has a phenotype intermediate to the two homozygote types. Ex: Snapdragon color RR= RedRr= Pinkrr= White Co-Dominance : Both alleles of a Heterozygote are expressed Ex: Blood Types I A – A Antigen I B - B Antigen i= no Antigen

8. M ULTIPLE A LLELES More than 2 alleles exist for some gene Means more phenotypes and genotypes to deal with. Ex: Coat color in rabbits C + - agouti C ch - chinchilla C h - Himalayan C- albino C + > C ch > C h > C

9. P OLYGENIC T RAITS Traits that are controlled by two or more genes Polygenic traits produce a lot of phenotypes One example of this is with skin color More than four different genes control this trait and that is why we have all the different ranges of color of human skin

10. S EX -L INKED Gene expressed usually in one sex Located on X choromosome Females – XX Males – XY 1. Hemophilia – failure of blood to clot 2. Color blindness- Can’t see certain colors 3. Muscular Dystrophy – wasting away muscles

11. 10. E XPLAIN WHAT A PEDIGREE IS AND WHY ONE WOULD USE IT. Pedigree: A CHART THAT SHOWS HOW A TRAIT AND THE GENES THAT CONTROL IT ARE INHERITED. 1. Sex-Linked? Usually seen only in males because they have 1 X If not, should be = distribution between sexes 2. Dominant or Recessive? Dom- every offspring that has it should have parent Rec- parent is a hetero, normal but a carrier