DNA 2 - Key Terms

• What is an allele?

  A different version of the same gene
• What is the difference between dominant and recessive alleles?

  Dominant alleles are expressed over recessive ones
• What does homozygous mean?

  Having two identical alleles for a gene
• What does heterozygous mean?

  Having two different alleles for a gene
• What is a genotype?

  The entire collection of alleles an organism has
• What is a phenotype?

  The observable characteristics from a genotype
• If a mouse is heterozygous for fur color with one allele for purple and one for green, what color will it be if purple is dominant?

  It will be purple
• What must be true for a mouse to be green?

  It must be homozygous recessive for green fur
• How does the expression of alleles work in a heterozygous mouse?

  Only the dominant allele is expressed
• How can two mice have the same phenotype but different genotypes?

  They can have different alleles but show the same trait
• What is the relationship between genotype and phenotype?

  Genotype determines the phenotype of an organism
• What are the key terms related to genes discussed in the video?

  • Allele
  • Dominant
  • Recessive
  • Homozygous
  • Heterozygous
  • Genotype
  • Phenotype
• What are the characteristics determined by genes?

  • Traits can be determined by a single gene
  • Traits can also be influenced by multiple genes
  • Examples include fur color and height
• What is the significance of having two alleles for each gene?

  • One allele inherited from each parent
  • Can be the same (homozygous) or different (heterozygous)
• What happens when a dominant allele is present?

  • It is always expressed in the phenotype
  • Recessive alleles are only expressed when homozygous
• How do genotypes affect phenotypes in mice?

  • Different genotypes can lead to the same phenotype
  • Example: Heterozygous and homozygous dominant mice can both be purple