PEDIGREES Chapter 14 Pedigree A pedigree is a
- Slides: 16
PEDIGREES Chapter 14
Pedigree • A pedigree is a chart for tracing genes in a family • They can be used to study the transmission of a hereditary condition • Phenotypes are used to infer genotypes on a pedigree
Symbols Used in a Pedigree ¢ ¢ ¢ Normal male Affected male Normal female Affected female A marriage with five children, two daughters and three sons. The middleaged son is affected by the condition. Vertical Lines- offspring Marriage/Mating Oldest child Youngest child
Organizing the Pedigree • Generations are identified by Roman numerals I II IV
Organizing the Pedigree • Individuals in each generation are identified by numbers. • Therefore the affected individuals are II 3, IV 2 and IV 3 I II IV
Patterns of Inheritance v Basic patterns of inheritance vautosomal, recessive vautosomal, dominant v. X-linked, recessive v. X-linked, dominant (very rare)
Autosomal Recessive Traits • Trait is rare in pedigree • Trait often skips generations • hidden in heterozygous carriers (sometimes shown half shaded) • Trait affects males and females equally
Autosomal Recessive Traits v Most common ones • Cystic fibrosis • Sickle cell anemia • Phenylketonuria (PKU) • Tay-Sachs disease v For each of these, over dominance (heterozygote superiority) has been suggested as a factor in maintaining the disease alleles at high frequency in some populations
Autosomal Recessive Trait • If you ever see this situation in the pedigree (two unaffected parents have an affected child) then the trait MUST be recessive! • The parents are heterozygous.
Autosomal Dominant Trait • Trait is common in the pedigree • Trait is found in every generation • Affected individuals transmit the trait to ~1/2 of their children (regardless of sex)
X-linked Recessive Trait • Trait is rare in pedigree • Trait skips generations • Affected fathers DO NOT pass to their sons, • Males are more often affected than females
X-linked Recessive Trait • ex. Hemophilia in European royalty
Steps to Determine Inheritance Pattern of a Trait Step 1: Determine whether it’s dominant or recessive. • Does it skip generations? YES= recessive NO= dominant. Step 2. Determine whether is is autosomal or x-linked. • Does it affect one gender more than the other? YES= X-linked NO= autosomal
What Inheritance Pattern Does this Trait Follow?
• What is the inheritance pattern? • What is the genotype of III-1, III-2, and II-3? • What are the odds that IV-5 would have an affected son?
Pedigree Analysis in Real Life • Remember: • dominant traits may be rare in population • recessive traits may be common in population • alleles may come into the pedigree from 2 sources • mutation happens • often traits are more complex • affected by environment & other genes
- Pedigrees edpuzzle
- Pedigree punnett square
- Pedigrees practice ap biology
- Whats an autosomal trait
- The karyotypel has a turner syndrome
- H h
- Pedigree chart dimples
- Pedigrees and karyotypes
- World pedigrees
- Part 10 pedigree charts
- Bdhhg
- Sex linked pedigree
- Hypertrichosis pedigree chart
- Pedigree chart
- Hearsay rule
- Phenotype pedigree chart
- How to read pedigree charts