Survey
* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project
Download Pedigrees notes - phsdanielewiczscience
Document related concepts
no text concepts found
Transcript
Pedigree Charts Chapter 14.1 Definition… • A pedigree illustrates a family history that shows how a trait is inherited over several generations. Basic Pedigree Symbols = female = male = marriage (or reproductive couple) = children Basic Pedigree Symbols (Continued) = female without trait = male without trait = female with trait = male with trait Patterns of Inheritance Rules 1. Is the trait located on a sex chromosome or an autosome? – The trait shows up only (or more often) in one sex • Autosomal – not on a sex chromosome • Sex Linked – located on the X chromosome – X-linked (recessive) - sons inherit the disease from normal parents 2. How is the trait expressed? – Dominant - the trait is expressed in every generation – Recessive - expression of the trait may skip generations Example 1: Albinism • Expressed in both sexes at approximately equal frequency. – Thus, autosomal • Not expressed in every generation. – Thus, recessive Albinism Example: Genotype the Affected Individuals • Assign codes for the alleles. – Code “A” for the dominant normal allele. – Code “a” for the recessive allele for albinism. • Affected individuals must be homozygous for “a.” • First generation parents must be “Aa” because they have normal phenotypes, but affected offspring. Albinism Example: Genotype the Normal Individuals • Normal individuals must have at least one “A.” Albinism Example: Parent-Offspring Relationships • #1 must transmit “a” to each offspring. • The “A” in the offspring must come from the father. • Normal father could be either heterozygous or homozygous for an “A.” ** How about genotype of individual #2? • Look at his children – homozygous OR heterozygous? – Could be either AA or Aa Example 2: Hemophilia • In this pedigree, only males are affected, and sons do not share the phenotypes of their fathers – Thus, hemophilia is linked to X chromosome – Thus, it is sex-linked • Expression of hemophilia skips generations – Thus, it is recessive Extensive bruising of the left forearm and hand in a patient with hemophilia. Hemophilia Example: Genotype of Affected Individuals • Assign codes for the alleles. – Code “h” for the recessive hemophilia allele. – Code “H” for the normal allele. • Affected individuals must have an “h” on an X chromosome. Hemophilia Example: Father-Daughter Relationship • All daughters of an affected father receive an X chromosome with the “h” allele. Hemophilia Example: Genotype of Normal Individuals • Normal individuals must have at least one X chromosome with the “H” allele Normal Phenotype: Homozygous or Carrier (heterozygous) • Pattern of Inheritance? – sex-linked, recessive • Normal Females – Carriers must have an affected father • Normal Males – must be homozygous as only have 1 X chromosome Pedigree Video https://www.youtube.com/watch?v=Wuk 0W10EveU
Related documents