Alleles

• What are dominant and recessive alleles?

  Types of alleles affecting traits
• What does homozygous mean in genetics?

  Having two identical alleles for a trait
• What does heterozygous mean in genetics?

  Having two different alleles for a trait
• What is the definition of genotype?

  Genetic makeup of an organism
• What is the definition of phenotype?

  Physical characteristics of an organism
• 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
• What is an allele?

  Version of a gene
• What does the earwax gene control?

  Earwax characteristics
• What are the two alleles for the earwax gene?

  Capital E and lowercase e
• What is the genotype for a person with two copies of the dry earwax allele?

  Lowercase e lowercase e
• What does it mean if a person is homozygous?

  They have two identical alleles
• What is the phenotype for a person with two alleles for dry earwax?

  Dry earwax
• What is the genotype for a person with two alleles for wet earwax?

  Capital E capital E
• What is the phenotype for a person with two alleles for wet earwax?

  Wet earwax
• What is the genotype for a person with one allele for wet earwax and one for dry earwax?

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

  They have two different alleles
• What phenotype does a heterozygous person for earwax have?

  Wet earwax
• What is a dominant allele?

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

  Shows in phenotype only with two copies
• How are most characteristics controlled?

  By many genes acting together
• What are the key definitions in genetics to learn?

  • Dominant alleles
  • Recessive alleles
  • Homozygous
  • Heterozygous
  • Genotype
  • Phenotype
• What is the relationship between alleles and phenotypes?

  • Alleles determine traits
  • Dominant alleles mask recessive ones
  • Phenotype is the observable trait
• How do dominant and recessive alleles interact in determining phenotypes?

  • Dominant alleles express traits with one copy
  • Recessive alleles express traits only with two copies
  • Heterozygous individuals show dominant traits