Inheritance of Traits Probability Carriers Autosomal Sexlinked Pedigrees

Inheritance of Traits üProbability üCarriers üAutosomal üSex-linked üPedigrees üComplex patterns of heredity üIncomplete dominance üCodominance üMultiple Alleles üPractice

Inheritance of Traits • Probability- the likelihood that a specific event will occur – When you flip a coin, there is a 50/50 chance it will land tails side up – If there are 4 kids in a family, probability says 2 will be girls and the other 2 will be boys

Inheritance of Traits • Carrier- an individual who is heterozygous for an inherited disorder but does not show symptoms. – Ex. Linda is a carrier for albinism. • Genotype-(Aa) • Phenotype- not albino • Even though she does not display the symptoms, she can still pass on albinism to her children.

Inheritance of Traits • Autosomal- when a gene is autosomal, it will appear in both sexes • Sex-linked- when a gene is sex-linked, it is found only on the X or Y chromosomes so the effects are only seen in males. – Remember, males are (Xy) and females are (XX) – Examples- colorblindness, hemophilia, Cystic Fibrosis and Sickle Cell Anemia

Inheritance of Traits • Sex-linked Punnett Square for colorblindness: X Xb X Key: XX- female Xy- male Xby- colorblind male y XXb- female carrier Xb. Xb- colorblind female What are the offspring?

Inheritance of Traits • Sex-linked Punnett Square for colorblindness: Xb X X Key: XX- female Xy- male Xby- colorblind male y XXb- female carrier Xb. Xb- colorblind female What are the offspring?

Inheritance of Traits • Sex-linked Punnett Square for colorblindness: Xb Xb y X Key: XX- female Xy- male Xby- colorblind male XXb- female carrier Xb. Xb- colorblind female What are the offspring?

Pedigrees • Pedigree- a family history that shows how a trait is inherited over several generations – Useful to track the carriers of genetic disorders in families – Can be used for both autosomal and sexlinked disorders

Pedigrees Pedigree for albinism: Key: Female (P 1) Male (F 1) Female carrier Male carrier (F 2) Female with albinism Male with albinism *The order of children is from left to right Married with children

Pedigrees • Pedigree for albinism: A B (P 1) C D E F G H (F 1) I J K (F 2) 1. Which individuals are heterozygous for albinism? 2. Which are homozygous for albinism? 3. Which individuals have albinism? 4. Which generations have an individual with albinism?

Complex Patterns of Heredity • Polygenic inheritance- when several genes influence a characteristic – Incomplete dominance – Codominance – Multiple alleles

Complex Patterns of Heredity • Incomplete dominance- when an individual displays an intermediate/middle phenotype of the parents – Ex. A red (RR) snapdragon flower is crossed with a white (rr) one and their offspring are pink (Rr)

Complex Patterns of Heredity • Codominance- when two dominant alleles are expressed at the same time – Ex. Blood types- AB blood A A B AB AB

Complex Patterns of Heredity • Codominance – Ex. Roan horses (have both red and white hair)

Complex Patterns of Heredity • Multiple alleles- genes with 3 or more possible alleles – Ex. Blood types- A, B, O (AB- codominant)

Practice Blood Type • If a man is homozygous for type B blood, and has a child with a homozygous woman with type A blood, what are the possible blood types of the child? Phenotype Genotype Type A AA or AO Type B BB or BO Type AB AB Type O OO

Practice Blood type • A man is heterozygous for type A blood and has a child with a woman that has AB blood. What are the possible blood types of the child? Phenotype Genotype Type A AA or AO Type B BB or BO Type AB AB Type O OO

Practice Incomplete dominance • Assume: – Red= RR – White = rr or WW or R’R’ – Pink= Rr or RW or RR’ You cross a red flower with a white flower: What happens?