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Understanding Genetics: Inheritance Patterns & Blood Types

Learn how chromosomes affect traits, including autosomal gene inheritance, sex-linked disorders, codominance, blood type determination, and gene mapping.

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Understanding Genetics: Inheritance Patterns & Blood Types

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  1. 7.1 KEY CONCEPT The chromosomes on which genes are located can affect the expression of traits.

  2. Two copies of each autosomal gene affect phenotype. • Mendel studied autosomal gene traits, like hair texture.

  3. (dominant) • Mendel’s rules of inheritance apply to autosomal genetic disorders. • Recessive disorder requires a homozygous recessive genotype to affect a person. A heterozygote for a recessive disorder is a carrier. • Disorders caused by dominant alleles are uncommon.

  4. Mendel’s rule only apply for autosomal genes(chromosome pairs 1-22). Genes on sex chromosomes are called sex-linked genes. • Y chromosome genes in mammals are responsible for male characteristics. Males have an XY genotype. • X chromosome genes in mammals affect many traits. Females have an XX genotype.

  5. Because males only have one copy of the X chromosome all of a male’s sex-linked genes are expressed. • In females, expression of sex-linked genes is similar to autosomal genes because they have two copies of the X chromosome. Y X

  6. Common examples of sex-linked disorders: • Duchenne’s muscular dystrophy • Hemophilia • Color Blindness

  7. The test to the left is simpler. The individual with normal color vision will see a 5 revealed in the dot pattern. An individual with Red/Green (the most common) color blindness will see a 2 revealed in the dots.

  8. X chromosome inactivation randomly “turns off” one X chromosome.

  9. In incomplete dominance, neither allele is completely dominant nor completely recessive.

  10. Codominant alleles will both be completely expressed.

  11. Codominant alleles are neither dominant nor recessive. • The ABO blood types result from codominant alleles. • Codominant alleles will both be completely expressed. • Many genes have more than two alleles.

  12. There are 3 alleles that determine blood type: IA, IB, and i • IA and IB are dominant to i. • IA and IB are codominant.

  13. Codominance

  14. Can receive from: A, O • Can donate to: A, AB • There are 4 blood types: • A : • Genotyple: IAIA or IAi • Antigen: A • Antibody: Anti-B   

  15. Can receive from: B, O • Can donate to: B, AB • B : • Genotyple: IBIB or IBi • Antigen: B • Antibody: Anti-A   

  16. Can receive from: A, B, AB, & O (universal recipient) • Can donate to: AB • AB : • Genotyple: IAIB • Antigen: A & B • Antibody: none  

  17. Can receive from: O • Can donate to: A, B, AB, & O (universal donor) • O : • Genotyple: ii • Antigen: none • Antibody: Anti-A and Anti-B   

  18. Rh Factor: Another surface marker which may or may not be present on the RBC. 

  19. Can receive from: Rh+ & Rh- • Can donate to: Rh+ • Rh+ : • Genotype: Rh+Rh+ or Rh+Rh- • Antigen: Rh • Antibody: none  

  20. Can receive from: Rh- • Can donate to: Rh- & Rh+ • Rh- : • Genotype: Rh-Rh- • Antigen: none • Antibody: Rh+

  21. Many genes have more than two alleles or multiple alleles used to express a trait.

  22. Order of dominance: brown > green > blue. • Polygenic traits are produced by two or more genes.

  23. An epistatic gene can interfere with other genes.

  24. Epistatic: recessive trait blocks another allele Black is dominant to chocolate B or bYellow is recessive epistatic (E or e)

  25. Phenotype can be a combination of genotype and environment. Malnourished Fed and cared for. Identical twins separated at birth and treated differently.

  26. 7.4 KEY CONCEPT A combination of methods is used to study human genetics.

  27. X Y • A karyotype is a picture of all chromosomes in a cell.

  28. Karyotypes can show changes in chromosomes. • Nondisjunction: an error in meiosis that results in an extra or a loss of a chromosome • deletion of part of a chromosome or duplication of part of a chromosome

  29. A pedigree is a chart for tracing genes in a family. • Phenotypes are used to infer genotypes on a pedigree. • Autosomal genes show different patterns on a pedigree than sex-linked genes.

  30. If the phenotype is more common in males, the gene is likely sex-linked.

  31. 7.3 KEY CONCEPT Genes can be mapped to specific locations on chromosomes.

  32. Mutant Wild type • Because of their location on a chromosome, some genes travel together and are considered to be linked.

  33. Linkage maps estimate distances between genes. • The closer together two genes are, the more likely they will be inherited together. • Linkage maps show the relative locations of genes.

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