DNA and Inheritance

• DNA


  • A polymer made of many nucleotide monomers
  • Made of 2 strands in the shape of a double helix
• Bases in DNA


  • A
  • T
  • C
  • G
• DNA base pairing rules

  • A pairs with T
  • C pairs with G
• Bases in DNA (Higher)

  • Adenine (A)
  • Thymine (T)
  • Cytosine (C)
  • Guanine (G)
• Transcription (Higher)


  1. DNA unzipped

  2. Complementary mRNA nucleotides bind and are joined together

  3. mRNA detaches and leaves the nucleus
• Translation (Higher)


  1. mRNA travels to a ribosome

  2. Carrier molecules carry specific amino acids to the ribosome based on the mRNA sequence

  3. The amino acids are joined together
• The sequence of DNA affects the protein made in protein synthesis (Higher)
• Genetic profiling


  A method of comparing DNA by cutting it into fragments and comparing the fragments with each other
• Uses of genetic profiling

  • Paternity testing (working out who is the biological parent of a child)
  • Forensic identification (matching a criminal to DNA left at a crime scene)
  • Matching an organism's DNA to classify it
• Benefits of genetic profiling

  • It can help to catch criminals
  • It can be used to identify the presence of disease-causing genes
• Ethical issues surrounding genetic profiling

  It could be used against people by insurance companies based on a person's predisposition to certain diseases
• Gene


  A section of DNA that codes for a protein
• Alleles


  Different versions of the same gene
• Chromosome


  Tightly packaged DNA around histone proteins
• Gametes


  Sex cells (sperm or eggs)
• Dominant allele


  A version of a gene where only one copy is needed for it to be expressed
• Recessive allele


  A version of a gene where two copies are needed for it to be expressed
• Homozygous


  When an organism has two copies of the same allele (two recessive or two dominant)
• Heterozygous


  When an organism has two different versions of the same gene (one dominant and one recessive)
• Genotype


  The genes present for a trait
• Phenotype


  The visible characteristic
• F1 generation


  The offspring produced when 2 organisms are bred together
• F2 generation


  The offspring produced when two offspring (F1 generation organisms) are bred together
• Selfing


  When gametes from the same parent fuse (e.g. when pollen from a plant lands on the stigma of that same plant)
• Dominant alleles in a Punnett square


  They are represented using uppercase letters
• Recessive alleles in a Punnett square


  They use the lowercase version of the same letter as the dominant allele
• Genetic engineering


  Altering the genome of an organism
• Transgenic organism


  An organism that contains foreign DNA
• Advantages of genetically modified crops

  • Better crop yields
  • Food will last longer and taste better
• Disadvantages of genetically modified crops

  • The new genes can easily spread to other plants in the environment
  • We don't know what long term effects GM crops cause on health