Inheritance

• What is DNA?

  A molecule containing genetic information
• What is the structure of DNA?

  It has a double-helix structure
• What are genes?

  Sections of DNA coding for proteins
• Where is each gene located?

  At a specific position on a chromosome
• What are chromosomes?

  Thread-like structures made of DNA and proteins
• How many chromosomes do humans have?

  46 chromosomes (23 pairs)
• What are autosomes?

  22 pairs of chromosomes that do not determine sex
• What are sex chromosomes?

  The 23rd pair that determines sex
• What chromosomes do females have?

  Two X chromosomes (XX)
• What chromosomes do males have?

  One X and one Y chromosome (XY)
• What are alleles?

  Different versions of a gene
• What is a dominant allele?

  Only one is needed for the trait to show
• How is a dominant allele represented?

  By a capital letter
• What is a recessive allele?

  Shows in phenotype if two copies are present
• How is a recessive allele represented?

  By a lowercase letter
• What is a genotype?

  The combination of alleles for a gene
• What is a phenotype?

  The physical expression of a genotype
• What does homozygous mean?

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

  Having two different alleles for a trait
• What is monohybrid inheritance?

  • Inheritance of a single characteristic
  • Controlled by one gene with two alleles
  • Classic example: Mendel’s pea plants
• How does a Punnett square work?

  • Parents’ genotypes placed along the top and side
  • Possible offspring genotypes filled inside the square
• What is the genotype ratio for two heterozygous parents (Bb x Bb)?

  1 BB : 2 Bb : 1 bb
• What is the phenotype ratio if B is dominant?

  3 with dominant trait : 1 with recessive trait
• What are the sex chromosomes in humans?

  XX for females, XY for males
• How is a child's sex determined during fertilization?

  Mother provides X, father provides X or Y
• What are inherited diseases and disorders?

  • Genetic disorders inherited in specific patterns
  • Typically through dominant or recessive alleles
• What is cystic fibrosis?

  A recessive disorder caused by allele f
• Who will have cystic fibrosis?

  Only individuals with genotype ff
• What are carriers of cystic fibrosis?

  Heterozygous individuals (Ff) without symptoms
• What is the Punnett square outcome for two carriers (Ff x Ff)?

  25% chance of unaffected child (FF)
• What is the chance of a carrier child from two carriers (Ff x Ff)?

  50% chance of a carrier child (Ff)
• What is the chance of a child with cystic fibrosis from two carriers (Ff x Ff)?

  25% chance of child with cystic fibrosis (ff)
• What causes genetic variation?

  • Mutations: Random changes in DNA sequences
  • Sexual reproduction: Unique combinations of alleles from parents
• What is a mutation?

  A change in the DNA sequence of a gene
• What are the types of mutations?

  Harmful, neutral, and beneficial mutations
• What are harmful mutations?

  Causing genetic disorders or cancer
• What are neutral mutations?

  Having no effect on the phenotype
• What are beneficial mutations?

  Providing a survival advantage
• What can cause mutations?

  Mutagens like UV radiation and chemicals
• What is the importance of mutation in evolution?

  • Beneficial mutations lead to adaptation
  • Natural selection favors individuals with advantageous traits