Genetics Lifes Blueprint Monogenic Traits aka Simple Inheritance

Genetics – Life’s Blueprint

Monogenic Traits aka Simple Inheritance • Each organisms has two or more versions of a trait. (Each version is called an allele) • Each organism inherits two alleles, one from each parent • A single gene appears to control the appearance of the trait

Monogenic Traits Simple Inheritance • One allele “dominates” when present • The other allele “recedes” when the dominant allele is present

Predicting Inheritance: Punnett Squares Each parent passes on ONE of their alleles • Through gamete (sperm or egg) Use Genotypes – represented by 2 letters ex: AA, Aa, aa Capital letter = dominant allele Lowercase letter = recessive allele Need 2 lowercase alleles to show a recessive version trait

Monogenic Inheritance Trait Studied – Flower Color Generation Phenotype Parents PP F 1 generation Pp F 2 generation PP Pp Expected Offspring Ratio 3 Phenotype pp pp 1

Punnett Squares -Monogenetic Crosses X

Punnett Squares and Prediction

Simple Monogenic Problems 1. Given the parents’ genotypes what are the offsprings’ possible phenotypes and ratios? 2. Given the parents’ phenotypes and the offsprings phenotypic ratios, what are the parents’ genotypes?

Law of Independent Assortment Observation – When two traits are followed, they don’t stay together Law – Each pair of alleles segregates independently of the other pairs of alleles during gamete formation

Punnett Squares – Two Independent Traits Gg. Ss x Gg. Ss GS GGSS GGSs Gs g. S gs GGSs Gg. SS Gg. Ss GGss Gg. Ss Ggss g. S Gg. Ss gg. SS ggs. S gs Gg. Ss Ggss gg. Ss ggss Phenotype Ratio Prob. Green Smooth 9/16 56% Green Wrinkled 3/16 19% Yellow Smooth 3/16 19% Yellow Wrinkled 1/16 6%

Multiple Independent Trait Problems 1. Given the parents’ genotypes what are the offsprings’ possible phenotypes and ratios? 2. Given the parents’ phenotypes and the offsprings phenotypic ratios, what are the parents’ genotypes?

More Genetics Incomplete Dominance Codominance Sex Linked Polygenic Traits

Incomplete Dominance

Codominance – Blood Type

an aside - Donors and Recipients Donor Blood Type A Type B Type AB Type O Type A - IA IA IAi Y N N Y Type B - IBIB Ibi N Y Type AB - IAIB Y Y Type O - ii N N N Y Recipient

Codominance Practice Problems

Sex-linked Traits mainly X , mainly recessive • • Muscular dystrophy Hemophilia Fabry’s disease colorblindness

Sex-linked Practice Problems

Polygenic Traits Most “phenotypic traits” are multiple gene interactions. In humans these include • • • Eye color Hair color Skin pigmentation Height Weight Intelligence (? )

Phenotypes and Polygenic Traits

Eye Color in Humans • More than 6 genes control eye color • Two genes on Chromosome 15 account for most of the eye color combinations

Hair Color At least 4 genes control hair color

Skin Color

f two Aa. Bb. Cc people would get married and have children, the Punnett square would look like this: The Ultimate Punnett Square If two heterozygous individuals (Aa. Bb. Cc) have a child, what is the probably that their child will be very dark skinned?

Pedigrees and Genetic Analysis

Pedigree Symbols

Pedigree Example Albinism (aa) is a recessive trait Based on the pedigree, what are the genotypes of the parents?

Genetics Problem Practice

Pedigree Practice