alleles

• What do homozygous and heterozygous refer to?

  Types of genotypes based on alleles
• What is the definition of alleles?

  • Versions of a gene
  • Control characteristics
  • Come in pairs
• How many pairs of chromosomes do normal human cells contain?

  23 pairs
• Where does one chromosome in a pair come from?

  From the father
• What are genes?

  Sections of DNA on a chromosome
• How many copies of every gene do humans have?

  Two copies
• What is the genotype of a person with two copies of the allele for dry earwax?

  Lowercase e lowercase e
• What does homozygous mean?

  Having two identical alleles
• What does phenotype refer to?

  Characteristics caused by alleles
• What is the genotype of a person with two alleles for wet earwax?

  Capital E capital E
• What does it mean if a person is heterozygous?

  They have two different alleles
• What is a dominant allele?

  Shows in phenotype with one copy
• What is a recessive allele?

  Shows in phenotype with two copies
• What is the difference between dominant and recessive alleles?

  • Dominant alleles show with one copy
  • Recessive alleles show only with two copies
• How are most characteristics controlled?

  • By many genes acting together
  • Example: Height