Genetic Diagrams

• Genetic Diagrams
• Some Characteristics are Controlled by Single Genes
• Characteristics controlled by single genes are called alleles, which are represented by Latin letters
• You have versions (alleles) of genes in your body
• If an organism has two identical alleles for a particular gene, they are called homozygous
• If an organism has two different alleles for a particular gene, they are called heterozygous
• Dominant alleles are represented by capital letters, recessive alleles by lowercase letters
• Genetic Diagrams Show the Possible Alleles of Offspring
• Breeding example


  • Dominant allele for behaviour (B)
  • Recessive allele for behaviour (b)
• Breeding frame with hamara hameter


  1. Possible offspring genotypes: BB, Bb, bb

  2. Possible offspring phenotypes: Normal behaviour, Normal behaviour, Abnormal behaviour
• All the Offspring are Normal
• There's a 1:1 Ratio in the Offspring
• Long hair is caused by dominant allele (W), short hair by recessive allele (w)
• You Need to be Able to Interpret Family Trees
• The allele for cystic fibrosis is dominant
• There is 25% chance that the new baby will have the disorder and 50% chance that it will be a carrier