Understanding Pedigrees: An Overview

Introduction

• Pedigrees are used to trace genetic traits throughout generations, similar to a family tree.
• Circles represent females and squares represent males.
• Roman numerals indicate generations.
• Lines connect parents to children and marriage lines connect partners.

Reading Pedigrees

• Shaded shapes indicate individuals expressing the trait being tracked.
• Example: Attached earlobes trait
  • Recessive and autosomal recessive trait.
  • Autosomal refers to non-sex chromosomes.

Genotype Identification

• Attached Earlobes: Recessive (ee)
  • Must be ee to express trait since it is recessive.
• Free Earlobes: Dominant (EE or Ee)
  • At least one dominant allele (E) for free earlobes.

Analyzing Family Pedigree

• Example family's pedigree with attached earlobes:
  • Father's genotype must be Ee as a carrier.
  • Paternal grandfather has attached earlobes (ee), paternal grandmother could be EE or Ee.
  • All offspring of the paternal grandparents must be Ee (heterozygotes).

Understanding Sex-linked Traits

• Sex-linked Pedigree: New example using a sex-linked recessive trait.
  • Females (XX) and males (XY) marked accordingly.
  • Example traits: color-blindness, male-pattern baldness.
  • Females can be carriers (XRXr) without expressing the trait.
  • Males express the trait if they inherit the recessive allele on the X chromosome (XrY).

Solving Pedigree Problems

• Check children's alleles to determine parent's genotype possibilities.
• Include all possible genotypes if the evidence allows.

Dominant Traits in Pedigrees

• Dominant traits require only one dominant allele to be expressed.
• Pedigrees may include half-shaded symbols to indicate carriers.

Conclusion

• Mapping pedigrees is crucial for understanding genetic disorders.
• Encouragement to stay curious and explore further into genetic studies.

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Stay curious and keep exploring genetic patterns with the Amoeba Sisters!