genetic modification and inheritance

• count chromosomes through centermore
• when DNA is replicated the chromosomes move away to the end of the cell
• there are 2 divisions that take place. first is the division of the chromosomes then the division of the chromatids'
• allele: different forms of a gene that arise by mutation and are found at the same place on a chromosome. there are 2 alleles for every single gene in your body
• homozygous: having two identical alleles of a particular gene or genes
• heterozygous: having two different alleles of a particular gene or genes
• dominant allele: the allele that is expressed in the phenotype when the individual has two copies of that allele. dominant allele overrides the recessive allele. always written with a capital letter
• recessive allele: the allele that is only expressed in the phenotype if an organism has two copies of it. never written with a capital letter
• genotype: your entire dna. the combination of alleles present in an individuals dna sequence
• DNA: has helix shape, giant polymer, double stranded, contains genetic information
• dna contains one nucleotide that consists of phosphate, sugar, and a base
• the base letters are: A T C G. a and t are always written together. c and g are always written together
• transcription: the process of copying the DNA into a single strand of MRNA. the mrna travels to find ribosome, where it is used to make a protein. mRNA uses U instead of the letter T
• translation: once the mRNA nucliotide binds to a ribosome, there is tRNA. the condons on the mRNA are read by the tRNA which brings amino acids to join together to form a polypeptide chain. (protein)
• genetic modification: is changing the genetic material of an organism by removing, changing or inserting individual genes
• examples: modifying crop plants to be resistant to herbicides or pests, or to contain additional vitamins that help communities with limited diets and malnutrition
• the first step of the process is to idenitfy the gene that needs to be inserted. before GMO takes place, the section of DNA to be transferred needs to be indentifed. e.g. the gene that codes for the insulin protein in humans
• once identified it can be cut using restrictive enzymes
• restrictive enzymes break the bonds in the DNA backbone, exposing the DNA bases at the site of the cut creating areas called sticky ends
• the next step is to prepare the bacterial plasmid. the plasmid is cut with the same type of restriction enzyme. this is important to ensure that they have the same exposed bases on their sticky ends for base pairing
• once the plasmid has been cut, we can take the human insulin gene and insert it into the gap. the bases of the sections of DNA join by complementary base pairing
• the name that is used to stick the 2 pieces of DNA together is called the ligase
• Restriction enzymes cut DNA strands at specific sequences to form ‘sticky ends’

  • The plasmid and the isolated gene are joined together by DNA ligase enzyme
  • If two pieces of DNA have complementary sticky ends, DNA ligase will link them to form a single, unbroken molecule of DNA
• Vectors & Recombinant DNA

  • Plasmids and viruses can act as vectors for genetic engineering
  • They take up pieces of DNA and then insert this recombinant DNA into other cells
  • Viruses transfer DNA into human cells or bacteria
  • Plasmids - transfer DNA into bacteria or yeast
• DNA ligase is used to join two separate pieces of DNA together

  • The genetically engineered plasmid is inserted into a bacterial cell
  • When the bacteria reproduce the plasmids are copied as well and so a recombinant plasmid can quickly be spread as the bacteria multiply and they will then all express the gene and make the human protein
  • The genetically engineered bacteria can be placed in a fermenter to reproduce quickly in controlled conditions and make large quantities of the human protein
• Genetic modification of bacteria

  To produce human insulin
• Gene to be inserted


  Located in the original organism (human chromosome)
• Isolating the human insulin gene

  1. Restriction enzymes used

  2. Gene left with 'sticky ends'
• Cutting the bacterial plasmid

  1. Same restriction enzyme used

  2. Plasmid left with corresponding sticky ends
• Joining the plasmid and isolated gene

  DNA ligase enzyme used
• DNA ligase


  Links DNA pieces with matching sticky ends into a single, unbroken molecule
• Inserting the recombinant plasmid

  Into a bacterial cell
• Bacterial reproduction


  1. Plasmids copied

  2. Recombinant plasmid spread as bacteria multiply

  3. Bacteria express the human insulin gene and make the human insulin protein
• Producing large quantities of human protein

  1. Genetically engineered bacteria placed in a fermenter

  2. Reproduce quickly in controlled conditions
• Bacteria


  • Contain the same genetic code as the organisms we are taking the genes from
  • No ethical concerns over their manipulation and growth
  • Presence of plasmids makes them easy to remove and manipulate to insert genes
• • Alleles can be dominant or recessive
  • A dominant allele only needs to be inherited from one parent in order for the characteristic to show up in the phenotype
  • A recessive allele needs to be inherited from both parents in order for the characteristic to show up in the phenotype.
  • If there is only one recessive allele, it will remain hidden and the dominant characteristic will show