genetic diagrams

• Alleles:

  • Dominant allele (capital A) codes for normal muscle
  • Recessive allele (lowercase a) codes for muscular mass
• Genetic diagrams show all different combinations of alleles from two parents
• Phenotype and Genotype of parents:

  • One parent is homozygous for normal muscle (genotype: capital A capital A, phenotype: normal)
  • Other parent is homozygous for muscular allele (genotype: lowercase a lowercase a, phenotype: muscular)
• Gametes:

  • Split the two letters in each parent's genotype into separate circles to represent gametes
• Offspring's Genotypes:

  • Combine the gametes from both parents to get all possible combinations
  • In this case, all offspring are heterozygous (genotype: capital A lowercase a)
  • Heterozygous offspring will have the normal phenotype
• Punnett Square:

  • A two by two grid showing combinations of gametes from both parents
  • Helps determine offspring genotypes and phenotypes
  • Simplifies the process of finding genetic outcomes
• Crossing two heterozygous mice:

  • Both parents have normal phenotype but genotype big A little a
  • Each parent gives one big A gamete and one little a gamete
  • Offspring will have one homozygous dominant, two heterozygous, and one homozygous recessive
  • Phenotypes: three normal and one muscular
• Interaction of Genes and Environment:

  • Multiple genes interact to determine traits
  • Outside environment can also influence traits
  • Example: genes for being tall, but lack of food or sleep can affect height