B6 - Inheritance, Variation and Evolution

• DNA Structure

  • Each strand DNA is bonded to another strand of DNA - DOUBLE HELIX
  • The specific ORDER OF BASES makes up DNA (A, T, C and G)
• Gene

  • A sequence of DNA which codes for proteins
• What is formed when amino acids are joined together?

  • Proteins
• What enzyme breaks proteins down into amino acids?

  • Protease
• What happens if a single base is changed?

  • The protein produced will be wrong because the sequence of amino acids is wrong
• How many daughter cells are produced in mitosis and how is it different to the gametes produced in meiosis?

  • 2 Daughter Cells
  • Are GENETICALLY IDENTICAL to parent cell
• Why does 'Crossing Over' occur in meiosis?

  • Causes variation
• What is produced in meiosis and how is it different to the cells produced in mitosis?

  • 4 Gametes
  • They're genetically different to one another
• How many Cell Divisions does MITOSIS and MEIOSIS undergo?

  MITOSIS:

  • 1

  MEIOSIS:

  • 2
• In both MITOSIS and MEIOSIS the contents inside the body cells what?

  • DOUBLES CHROMOSOMES
• What type of reproduction is Mitosis?

  • Asexual
• What type of reproduction is Meiosis?

  • Sexual
• How many chromosomes are in each daughter cell at the end of MITOSIS?

  • 46
• How many chromosomes are in each gamete at the end of MEIOSIS?

  • 23
• Genotype

  • The sequence of genes in an organism
• Phenotype

  • Characteristic seen as a result of the genotype
• Allele

  • Different versions of the same gene
• Dominant

  • ALWAYS expressed if PRESENT
• Recessive

  • ONLY expressed if dominant allele is NOT expressed
• Homozygous

  • 2 of the same alleles
• Heterozygous

  • A combination of recessive + dominant alleles
• Females have 2 what chromosomes?

  • XX
• Males have 2 what chromosomes?

  • XY
• What is the percentage of getting either a boy or girl at birth?

  • 50%
• What is polydactyly caused by?

  • Presence of a DOMINANT allele
• What is cystic fibrosis caused by?

  • Presence of a RECESSIVE allele
• Steps to encountering a PEDIGREE DIAGRAM?

  1. Identify 2 parents WHO DO NOT have the disease
  2. Look at their children to see if any DO HAVE the disease
  3. If a child is infected = Recessive allele
  4. If no children have been infected = Dominant allele
• Genome

  • The entire genetic material of an organism