Alleles

• How many pairs of chromosomes do normal human cells contain?

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

  One comes from the father and the other from the mother
• What are genes?

  Sections of DNA on a chromosome
• What does it mean that chromosomes come in pairs?

  It means there are two copies of every gene
• What is the gene that controls earwax?

  The earwax gene
• How many alleles does the earwax gene have?

  Two alleles
• What does the allele symbol capital E represent?

  Wet earwax
• What does the allele symbol lowercase e represent?

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

  Lowercase e lowercase e
• What does homozygous mean in genetics?

  Having two copies of the same allele
• What does phenotype refer to?

  The characteristics caused by a person's alleles
• What is the phenotype of a person with two alleles for dry earwax?

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

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

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

  Capital E lowercase e
• What does heterozygous mean in genetics?

  Having two different alleles
• What phenotype does a person with one allele for wet earwax and one for dry earwax have?

  Wet earwax
• What is a dominant allele?

  An allele that shows in the phenotype even if there's only one copy present
• What is a recessive allele?

  An allele that shows in the phenotype only if two copies are present
• What is the difference between dominant and recessive alleles?

  • Dominant alleles show in the phenotype with one copy.
  • Recessive alleles show in the phenotype only with two copies.
• What are homozygous and heterozygous genotypes?

  • Homozygous: Two copies of the same allele.
  • Heterozygous: Two different alleles.
• How are most characteristics controlled in genetics?

  • Most characteristics are controlled by many genes acting together.