Inheritance of Traits

1. Inheritance of Traits Probability Carriers Autosomal Sex-linked Pedigrees Complex patterns of heredity Incomplete dominance Codominance Multiple Alleles Practice

2. 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

3. 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.

4. Inheritance of Traits • Autosomal- when a gene is autosomal, it will appear in both sexes equally

5. Inheritance of Traits • Sex-linked- when a gene is sex-linked, it is found only on the X chromosome so the effects are seen in males more often than females • Remember, males are (Xy) and females are (XX) • Examples- colorblindness, hemophilia, Cystic Fibrosis and Sickle Cell Anemia

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

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

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

9. Sex linked: • Sometimes you can write sex linked genotypes like this: (N = normal; n= abnormal) • XNXN • XNXn • XnXn XNy Xny

10. 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 sex-linked disorders

11. Pedigree Key • Circle- female Square- male • Clear circle/square- does not show trait/disorder • Shaded circle/square- has trait disorder • Carries can be displayed several different ways: • half will be shaded • it will be clear with a line through the middle • it will be clear • Horizontal line between circle and square indicates two married people • Vertical line extending from a parent line leads to offspring • The order of children is left to right

12. Key: Female Male Female carrier Male carrier Female with albinism Male with albinism (P1) (F1) (F2) Married with children Pedigrees Pedigree for albinism (autosomal): *The order of children is from left to right

13. (P1) (F1) (F2) Pedigrees B • Pedigree for albinism (autosomal): A D C E F G H I J K • Which individuals are heterozygous for albinism? • Which are homozygous for albinism? • Which individuals have albinism? • Which generations have an individual with albinism?

14. Pedigree for colorblindness (sex-linked- X-linked Recessive Trait)

15. A F • How many males are colorblind? • How many females are colorblind? • What is the genotype for square A? • What is the genotype for circle F? • Is circle F colorblind? • What is the genotype for circle X? X

16. Complex Patterns of Heredity • We have been talking about “Mendelian Genetics” where the phenotype of one allele dominants over another • Now were are going to talk about “Non Mendelian Genetics” • Intermediate inheritance • Polygenic inheritance • Incomplete dominance • Codominance • Multiple alleles

17. Intermediate Inheritance • Intermediate inheritance- when the heterozygous offspring (Bb, Rr, etc) display a trait that is not exactly like either parent • One trait DOES NOT simply dominate over the other

18. Polygenic Inheritance • Polygenic inheritance • Many genes contribute to the phenotype • Provides genetic variation • Examples: • Skin color, hair color, height

19. Incomplete domiance • Incomplete dominance- when an individual displays an intermediate/middle phenotype of the parents (neither is dominate or recessive) • Ex. A red (RR) snapdragon flower is crossed with a white (rr) one and their offspring are pink (Rr) R R r Rr Rr r Rr Rr

20. PracticeIncomplete 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?

21. Incomplete Domiance • Cross a red flower with a pink flower • What happens? R R R RR RR r Rr Rr

22. Codomiance • Codominance- when two dominant alleles are expressed at the same time • Ex. Roan horses • have both red AND white hair

23. Codominance Practice • Assume: • Red= RR • White = rr or WW or R’R’ • Red and White= Rr or RW or RR’ You cross a red horse with a white horse: What happens?

24. Codominance • Another example of codominance is blood type • If someone has AB blood that means they have both A blood AND B blood A A B AB AB B AB AB

25. Multiple Alleles • Multiple alleles- more than 2 forms of a gene are expressed • Example- rabbit coat color • It isn’t just black OR brown; brown OR white • Rabbit fur could be brown, black, white, or a combination of black and white

26. Multiple Alleles • Another common example of multiple alleles is blood type • IAIA = homozygous dominant A blood • IBIB =homozygous dominant B blood • IAIB = heterozygous but has both A and B blood (is also codominant) • iOiO = homozygous recessive

27. PracticeBlood 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 Type B Type AB Type O AA or AO (IAIA or IAiO) BB or BO (IBIB or IBiO) AB (IAIB) OO (iAiB)

28. PracticeBlood 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 Type B Type AB Type O AA or AO (IAIA or IAiO) BB or BO (IBIB or IBiO) AB (IAIB) OO (iAiB)