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Pedigrees

Pedigrees. H. Biology Ms. Kim. Many human traits follow Mendelian patterns of inheritance. Humans are not convenient subjects for genetic research However, We use pedigrees !. The Study of Human Genetics Continues to Advance…. Can’t use humans We use pedigrees

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Pedigrees

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  1. Pedigrees H.Biology Ms.Kim

  2. Many human traits follow Mendelian patterns of inheritance • Humans are not convenient subjects for genetic research • However, • We use pedigrees! The Study of Human Genetics Continues to Advance… • Can’t use humans • We use pedigrees • A family tree that describes the interrelationships of parents and children across generations • Can also be used to make genetic predictions about future offspring

  3. Pedigrees • How do you create a pedigree? • Collect information about a family’s history • Organize the information in a family tree • Apply Mendel’s concepts and principles A pedigree is a family tree that traces specific traits across many generations Pedigrees help us determine whether alleles are recessiveor dominant

  4. First generation (grandparents) ww ww Ww Ww Ff Ff ff Ff Second generation (parents plus aunts and uncles) ww Ww Ww ww Ww Ff ww ff Ff FF or Ff Ff ff Third generation (two sisters) ff ww FF or Ff WW or Ww No Widow’s peak Free earlobe Widow’s peak Attached earlobe (a) Dominant trait (widow’s peak) (b) Recessive trait (attached earlobe) Inheritance patterns of particular traitscan be traced and described using pedigrees Figure 14.14 A, B

  5. Pedigree Basics Males = Square Females = Circle Horizontal Line = Mating BASIC SYMBOLS:

  6. Pedigree Basics Offspring are drawn below the parents What gender are the offspring pictured here? Note: Adopted children have a dotted line… BASIC SYMBOLS:

  7. OTHER SYMBOLS ADOPTION DIVORCE TWINS DEATH

  8. Pedigree Basics • By coloring in the shapes you are… • …indicating an expressed trait/phenotype

  9. Pedigree Basics  USUALLY IN IN SEX-LINKED Homozygous Homozygous Heterozygous • By using Mendel’s concepts and principles: • Can determine if a trait is: • Dominant or Recessive • Sex-linked or Autosomal • Can determine genotypes

  10. It will show up in every generation: What would a dominant trait look like in a pedigree?

  11. It will not be in every generation: What would a recessive trait look like in a pedigree? WHY?

  12. Practice ? ? ? ? ? What genotype MUST II-4 and II-5 have? What about III-4 and III-10 ???  BOTH must be Ff • III-4 MUST be Ff  III-10 could be FF or Ff

  13. How will I know if a trait is sex-linked? Males are more likely to have sex-linked disorders, b/c they only need one affected X chromosome (XY)! • Y- linked: • Only males will express trait • X-linked: • Females andmales will express trait • There will be a bias for males to express trait • WHY?

  14. What would an X-linked trait look like in a pedigree?

  15. Example of Pedigree Charts • Is it Autosomal or X-linked?

  16. Recessively Inherited Disorders • Many genetic disorders are inherited in a recessive manner • Need 2 recessive alleles (ex: ff) • Some people can be carriers • heterozygous individuals, who carry recessive allele but are show “normal” phenotype • Ff  carry the cf gene (“f”) but don’t have the disorder b/c you have to be ff (recessive)

  17. Mating of Close Relatives • Matings between relatives • Can increase the probability of the appearance of a genetic disease • Are called consanguineous matings • Increases changes of inheriting mutated alleles (ex: lethal mutations)

  18. What is a genetics counselor? • Creates pedigrees • Analyzes information for parents • Can tell parents the risk of passing disorders/diseases to offspring

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