Applications in Inheritance

• What does PKU stand for?

  Phenylketonuria
• What causes PKU?

  A mutation in a gene coding for an enzyme
• What is the inheritance pattern of PKU?

  It is a recessive trait
• How many recessive alleles must a person have to have PKU?

  Two recessive alleles
• Why can't babies with PKU drink breast milk?

  It contains phenylalanine, which they cannot process
• What must both parents have for a child to inherit PKU?

  At least one copy of the recessive allele
• What happens to phenylalanine in babies with PKU?

  It builds up in the blood
• What are SNPs?

  Single nucleotide polymorphisms
• What do SNPs signify?

  Different alleles at specific gene positions
• How many alleles can an individual inherit for a trait?

  Two alleles
• How many versions of the S gene exist in apples?

  32 versions
• How is the type A allele written?

  I$A$
• What does co-dominance mean?

  Both alleles are expressed in the phenotype
• What is the phenotype of a person with type A and type B alleles?

  Both A and B antigens are expressed
• What is the genotype for type O blood?

  Two recessive alleles
• What is the expected ratio of offspring from a type O mother and type AB father?

  1:1 ratio of type A and type B blood
• What does a Punnett square illustrate?

  The possible offspring genotypes from parents
• What is the difference between genotype and phenotype?

  Genotype is genetic makeup; phenotype is expression
• What is the notation for co-dominance in alleles?

  Different uppercase letters for each allele
• What is incomplete dominance?

  Heterozygous individuals have an intermediate phenotype
• What is the phenotype of a heterozygous individual in incomplete dominance?

  An intermediate phenotype, like pink flowers
• What are the sex chromosomes in humans?

  X and Y chromosomes
• What is the genotype for biological females?

  XX genotype
• What is the genotype for biological males?

  XY genotype
• What is the probability of having a male child from an XY male and XX female?

  50% chance of having a male child
• What differentiates male offspring from female offspring?

  The type of sperm carrying X or Y chromosome
• What are sex-linked genes?

  Genes present on sex chromosomes
• How are sex-linked genes written?

  As exponents on the X chromosome
• Why do sex-linked genes affect males and females differently?

  They are located on sex chromosomes