NON-MENDELIAN INHERITANCE PATTERNS (Modes of Inheritance) H. Biology Ms. Kim

1. NON-MENDELIAN INHERITANCE PATTERNS (Modes of Inheritance) H. Biology Ms. Kim

2. Review….. • What is Complete dominance? • Occurs when the phenotypes of the heterozygote (Hh) and dominant homozygote (HH) are identical • Demonstrates (follows) “Mendelian Genetics” • “Either” “Or” • EXAMPLE: • HH=Tall; Hh=Tall; hh=Tall • HH and Hh are both dominant and hh shows recessive

3. Sometimes… • Inheritance patterns do NOT follow the phenotype patterns (ex: 3:1) that Mendel saw in his pea plants • These patterns are called “Non-Mendelian” Genetic Inheritance Patterns

4. “Non-Mendelian Genetics” Incomplete (Intermediate) Dominance • 1 allele is not completely dominant over the other, so the heterozygote (Hh) has intermediate (or mixed) phenotype between 2 alleles

5. What is Incomplete Dominance? • Neither allele is completely dominant or recessive • Incomplete Dominance – type of inheritance when the heterozygous phenotype is a mixture of the two homozygous phenotypes • Example: • Green beta fish (CGCG) • Blue beta fish (CBCB) • Teal beta fish (CGCB) • CBCB x CGCG = teal beta fish

6. P Generation White CWCW Red CRCR  Gametes CR CW Pink CRCW F1 Generation 1⁄2 1⁄2 Gametes CR CR 1⁄2 Sperm 1⁄2 CR CR Eggs F2 Generation 1⁄2 CR CR CR CR CW 1⁄2 Cw CW CW CR CW Figure 14.10

7. Incomplete Dominance Problem #1 CRCW • Parent Genotypes  CRCR x CRCW If a red four o’clock flower is crossed with a pink four o’clock flower what will their offspring look like? CRCR = red CWCW = white = pink

8. Perform cross KEY CRCR = red CWCW= white CRCW = pink CR CW 2 CRCR : 2 CRCW 50% Red flowers & 50% Pink! CRCR Genotype ratio: Phenotype ratio:

9. Incomplete Dominance Problem #2 CRCR x CWCW 4 CRCW and 100% pink In the four-o’clock plant, homozygous shows the red flower color and homozygous shows the white flower color. Cross a red plant with a white plant and list the genotypic and phenotypic ratios.

10. Let’s do some practice problems… • Assume incomplete dominance… • A red gummy bear mates with a yellow gummy bear. Red (R) is dominant. What are the genotype/phenotype ratios of their F1 offspring? • 100% Rr 100% orange • If 2 F1 gummy bears from the question above mate. What are the genotype/phenotype ratios of their F2 offspring? • 25% RR 50% Rr 25% rr • 25% Red 50% orange 25% yellow

11. “Non-Mendelian Genetics” Codominance • “Co” means TOGETHER • 2 dominant alleles affect phenotype in separate, distinguishable ways • BOTH phenotypes are present • Ex’s of codominance • Speckled flower color • Roan animals (cattle & horses)

12. What is Codominance? CR CB • When both the dominant and recessive trait is expressed completely • Neither allele is dominant or recessive • Example: A flower that is homozygous for red flowers (CRCR) is crossed with a plant that is homozygous for blue color (CB CB). The offspring (CR CB) will have spots of blue and spots of red but NO purple • CRCRx CBCB= blue andred spotted

13. Roan Animals Show Codominance

14. Codominance Example • In cattle, fur color can either be red (CRCR), white (CWCW) or roan (CRCW). • Roan fur is both red hairs and white hairs together

15. Codominance Example #1 CRCR CRCw CwCw Cross a roan cow with a red cow Parents = CRCw x CRCR CRCw CR CR Genotype ratio: Phenotype ratio: 2 CRCR : 2 CRCW 50% Roan, 50% Red • Roan is a coat color found in some cows • = red hair • = red and white hair (Roan) • = white hair

16. Let’s do some practice problems… • Assume codominance… • A blue flower mates with a yellow flower. Blue (B) is dominant. What are the genotype/phenotype ratios of their F1 offspring? • 100% BY 100% Blue AND yellow flowers • If 2 F1 flowers from the question above mate. What are the genotype/phenotype ratios of their F2 offspring? • 25% BB 50% BY 25% YY • 25% Blue 50% blue AND yellow 25% yellow

17. Multiple Alleles/Codominance • Most genes can be found in more than 2 forms  multiple alleles • A type of inheritance pattern that involves: • 3+ alleles that influence gene’s phenotype • 4+ phenotypes can occur instead of only 3 • Ex: Human Blood type • There are 3 alleles (A,B,O) • We write the alleles: • A = IA • B = IB • O = i • When combined, they create 4 blood phenotypes: A, B, AB, O

18. Table 14.2 The ABO blood group in humansIs determined by multiple alleles (similar to codominance)

20. Blood Type Key • A Blood Type • Homozygous Type A  IAIA • Heterozygous Type A  IAi • B Blood Type • Homozygous Type B  IBIB • Heterozygous Type B  IBi • AB Blood Type (codominant)IAIB • AB is the universal receiver • O Blood Type (recessive) ii • O – is the universal donor

21. Blood Type

22. Blood Type Answers

23. Example Problem Genotype Ratio: 2 IAi: 2 IBi Phenotype Ratio: 50% A Blood Type 50% B Blood Type i i A type AB woman marries a type O man. What are the possible genotypes of their offspring? Phenotype AB x O Genotype IAIB x ii IA IB

24. Blood Type Practice • What are the possible blood types of a child who's parents are both heterozygous for "B" blood type? • IBi X IBi • 50% chance IBi, 25% chance IBIB, 25% chance ii • 75% chance of B type and 25% chance of O type • What are the chances of a woman with Type AB and a man with Type A having a child with Type O? • IA? x IAIB • 0% chance of Type O b/c mom can’t donate “i” allele • Jill is blood Type O.  She has two older brothers with blood types A & B.  What are the genotypes of her parents? • IAi and IBi

25. Polygenic Inheritance • 2 or more genes affect 1 phenotype • “Poly” also means many • “Genic” has to do with genes • Traits that can have a wide range of color • Ex: • Height, skin color, eye color

26.  AaBbCc AaBbCc aabbcc Aabbcc AABBCc AABBCC AaBbcc AaBbCc AABbCc 20⁄64 15⁄64 Fraction of progeny 6⁄64 1⁄64 SKIN COLOR: 6 genes involved Figure 14.12

27. Nature and Nurture: The Environmental Impact on Phenotype • Another departure from simple Mendelian genetics the phenotype depends on environment as well as on genotype • Called multifactorial inheritance • Ex: identical twins looking different hydrangea flowers