04/10/12 1.What does heterozygous mean? 2.What does homozygous mean? 3.What is a phenotype? 4.What is a genotype? 5.What three genotypes can an organism have for a trait?

When Heredity Follows Different Rules

Simple Mendelian Inheritance o Inheritance controlled by dominant and recessive paired alleles. Purple FF White ff Pure- breeding P generation Hybrid F1 generation Purple Ff Purple Ff Purple Ff Purple Ff x

BUT... It gets a little more complicated than that

Incomplete Dominance When one allele is not completely dominant over another.

In Mendelian Inheritance, Heterozygous and Homozygous Dominant Individuals have the same phenotype. Purple FF White ff Pure- breeding P generation Hybrid F1 generation Purple Ff Purple Ff Purple Ff Purple Ff x FF or Ff = Purple Flowers ff = White Flowers

In incomplete dominance, the heterozygous phenotype is between the two homozygous phenotypes. Homozygous Heterozygous Homozygous

How do we create a punnett square for Incomplete dominance?? RRR’R’ R R R’ RR’ x

Now you try one A Heterozygous snapdragon flower is crossed with another Heterozygous snapdragon flower. What Genotypes and Phenotypes could the offspring potentially have? x RR’

R RR’ R R’ R R’ 25% RR 50% R R’ 25% R’ R’ 25% Red 50% Pink 25% White

Codominance When two dominant alleles are expressed at the same time.

In Codominance, codominant alleles cause the phenotypes of both homozygotes to be produced in heterozygotes. BB BWWW

x BBWW BB W W BW

Now you try one A Heterozygous Chicken is crossed with a Homozygous White Chicken. What Genotypes and Phenotypes could the offspring potentially have? WWBW

WW B W WW BW 50% BW 50% WW 50% Checkered 50% White

Now For Some More Practice!!

Multiple Alleles 1. Read about Multiple Alleles on Page 317 in your text book. 2. When finished, turn to page 318 and complete Problem- Solving Lab 12-2 ** Answer all of the questions under Think Critically