genetic inheritance

• What is a gamete?

  A reproductive cell that contains half the number of chromosomes
• What is a chromosome?

  A long strand of DNA that contains many genes
• What is a gene?

  A section of DNA that codes for a specific trait
• What is an allele?


  Different versions of the same gene
• What does it mean if an allele is dominant?


  It is expressed even if only one copy is present
• What does it mean if an allele is recessive?


  It is only expressed if two copies are present, with no dominant allele
• What does homozygous mean?


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


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


  The genetic makeup of an organism, showing the alleles present
• What is a phenotype?

  The observable characteristics or traits of an organism
• What are the key concepts of single-gene inheritance?

  • Traits controlled by a single gene
  • Dominant allele determines phenotype if present
  • Recessive trait expressed only with two recessive alleles
• What is the purpose of a Punnett square?

  • Predicts probability of offspring inheriting traits
  • Shows all possible combinations of alleles from parents
  • Describes likelihood of dominant and recessive traits
• What is the genotype ratio from the example Punnett square for eye color?

  1 BB : 2 Bb : 1 bb
• What is the phenotype ratio from the example Punnett square for eye color?

  3 Brown eyes : 1 Blue eyes
• How does multiple gene inheritance differ from single-gene inheritance?

  • Most traits controlled by multiple genes
  • Inheritance is more complex than single-gene model
• How can Punnett squares and probability be used in genetics?

  • To predict traits in offspring
  • To understand inheritance patterns
• What are inherited disorders?


  Genetic disorders passed from parents to offspring through specific alleles.
• How can inherited disorders be classified?

  They can be classified as either dominant or recessive.
• What is polydactyly?

  • A genetic disorder caused by a dominant allele.
  • Individuals may have extra fingers or toes.
  • One copy of the dominant allele (Pp or PP) is sufficient for the disorder.
• What is required for a person to have cystic fibrosis?

  A person must inherit two copies of the recessive allele (ff) from each parent.
• What is the chance of a child having cystic fibrosis if both parents are carriers?

  There is a chance the child could have cystic fibrosis (ff) or be a carrier (Ff).
• What is embryo screening?


  • A process to test embryos for genetic disorders before implantation.
  • Used during In Vitro Fertilisation (IVF).
• What are the advantages of embryo screening?


  • Prevents inheritance of serious genetic conditions.
  • Reduces suffering for the child and family.
  • Lowers long-term healthcare costs.
• What are the disadvantages of embryo screening?


  • Ethical concerns about acceptable embryos.
  • Economic impact due to high costs and access issues.
  • Social issues regarding pressure to select against certain traits.
• What is gene therapy?


  It is a technique used to treat or prevent genetic disorders by altering genes in an individual's cells.
• What ethical questions are raised by gene therapy?

  Concerns about long-term effects and fairness of access.
• What factors should students consider when discussing embryo screening and gene therapy?

  • Ethical factors
  • Social factors
  • Economic factors