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ADVANCED GENE INTERACTIONS

Explore the complexities of gene interactions beyond simple dominance and recessiveness. This article teaches about incomplete dominance, where phenotypes blend to create new visual traits, and codominance, where both alleles are equally expressed in the phenotype. Learn through examples like flower color (red, pink, white) and animal fur patterns (roan). Additionally, delve into human blood types and the influence of sex-linked traits such as hemophilia and color blindness, providing comprehensive insights into inheritance patterns.

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ADVANCED GENE INTERACTIONS

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  1. ADVANCED GENE INTERACTIONS

  2. Genes interact in more complex ways than SIMPLE dominant / recessive ways Dom./Recess. Only 2 phenotypes Incomplete Dom. At least 3 pheno. / 3rd is a blend Codominance at least 3 pheno. that are all shown separately red pink white H W T I E

  3. 2. INCOMPLETE DOMINANCE: -active dominant allele does NOT fully compensate for inactive recessive allele -phenotype = a visual “blend” of dom. and recess. alleles Ex: R= red r = white Homozygous dom. mom X homo. recess. dad

  4. 3. CODOMINANCE: -both alleles are equally active and displayed in phenotype (dominant together) -written differently: both letters capital, since both dominant R = Red B = brown RB = roan Mom=Purebred red Dad = roan

  5. Practice ROAN PINK R = red r = white B = brown Rr = RB = What are phenotype % for the following crosses: 1. red mom & pink dad (incomplete dominance) 2. roan mom with a roan dad (codominance) 3. What would be the best mom genotype to cross with a ROAN dad, if you wanted to eliminate purebred red from the offspring phenotype %? 4. What would be the best mom genotype to cross with a pink dad, if you wanted the largest variety of phenotype % in offspring?

  6. 4. SICKLE CELL ANEMIA -A = normal hemoglobin -a = sickle hemoglobin -incomplete dominance -oxygen depravation causes hemoglobin to crystalize, making cells into sickle cells -being hetero. is good if malaria is common

  7. 5. Multiple Alleles: -some ALLELES exist in more than 2 forms (each organism still has ONLY 2 forms of each gene, regardless of how many are in the genome)

  8. Human Blood Types IA = A IB = B i = O GENOTYPE PHENOTYPE GENOTYPE PHENOTYPE

  9.     TYPES     DISTRIBUTION RATIOS O + 1 person in 3 38.4%      O - 1 person in 15 7.7%      A + 1 person in 3 32.3%      A - 1 person in 16 6.5%      B + 1 person in 12 9.4%      B - 1 person in 67 1.7%     AB + 1 person in 29 3.2%     AB - 1 person in 167 0.7%

  10. Practice 1. What are the GENOTYPE and PHENOTYPE % of a type AB mom crossed with a heterozygous type B dad? 2. What are phenotype % for a cross between: heterozygous type A mom and a heterozygous type B dad?

  11. 6. Sex Linked Traits = If a gene exists ONLY on the X chromosome, it is considered a SEX LINKED TRAIT

  12. Practice: A ) hemophilia H= non-hemo. h=hemo. Mom = XH Xh Dad = Xh Y Mom = Dad =

  13. B) XL = long wings Xl = short wings Mom = Heterozygous (short wing carrier) Dad = long wings 1. What are phenotype ratios for cross? 2. What percentage of females are carriers for short wings?

  14. C) colorvision XB = normal color vision Xb = color blindness Mom = carrier for color blindness Dad = color blind a. What % of offspring are colorblind? B. What % of offspring are carriers? C. In any sex linked situation, what % of MALES will be carriers for a recessive gene?

  15. two or more genes are LINKED if: a) they are on same chromosome b) they are close enough to stay together through almost all crossing over

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