GCSE Combined Science (AQA)

622 videos | 38 hours

Family Trees

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Inheritance, Variation and Evolution Reproduction

Family Trees

4:42 Genetic Crosses and Family Trees
Spec 4.6.1.6
Previous Drawing Punnett Squares Next Phenotype
  • Family trees display relationships and inheritance across generations, with the youngest members at the bottom.
  • In biology, family trees illustrate the inheritance of traits over generations.
  • Family trees in biology typically have the newest members at the bottom, progressing to the oldest at the top.
  • Family trees use a key to indicate characteristics and gender: males with squares, females with circles, and traits like polydactyly shown by filled shapes.
  • Polydactyly is a trait caused by a dominant allele (represented as "D").
  • By analyzing a family tree, one can determine the genotype of individuals, such as identifying if a person has polydactyly (dominant allele present) or is homozygous recessive (both alleles recessive, indicated by absence of polydactyly).
  • The example explains that person one has a genotype of "Dd" (heterozygous) because they have polydactyly and their child (person four) does not, indicating the presence of a recessive allele.
  • Family trees help in predicting genetic traits and understanding the inheritance patterns within a family, useful for both academic studies and practical applications like genetic counseling.

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