Cloning and Gene Tech

• Micropropagation


  - Taking small pieces of plant (called explants) and growing into a whole new plant

  - asexual reproduction/one parent
• Clone


  -offspring that are genetically identical to the parent

  - asexual reproduction, one parent
• Transgenic


  - Organism that contains DNA from a different species

  - e.g. bacteria containing human insulin gene
• Restriction enzyme


  - opens the plasmid so new genes can be inserted

  - also cuts out the required gene

  - "genetic scissors"
• vector


  - organism that carries the gene from the different species

  - e.g. bacteria is used as a vector to carry human insulin
• Ligase


  - closes the plasmid after the extra gene has been inserted

  - "genetic glue"
• Genetic modification


  - changing the DNA of an organism to include a useful gene

  - e.g. drought resistance in plants
• enucleated


  - removal of haploid nucleus from egg cell during cloning
• Haploid


  - cell with half the normal DNA content

  - e.g. sperm, egg, pollen, ovum
• Diploid


  - cell with full amount of DNA content

  - e.g. any body cell other than gamete
• Differentiation


  - where cells become specialised in their structure/function
• Specialised cell


  - cells have special structure to carry out their function

  - e.g. red blood cells (no nucleus so more space for haemoglobin)
• Stem cell


  - undifferentiated cell that has the potential to become other cells

  - e.g. embryonic cells/umbilical cord
• Clones


  - two individuals that are genetically identical to each other

  - formed in mitosis

  - causes two daughter diploid cells
• 2 methods for cloning plants (artificial propagation)


  - asexual reproduction (taking cuttings)

  - tissue culture
• Asexual reproduction of plants method


  - produces genetically identical offspring

  - taking cutting enables new plants to be obtained quickly and cheaply

  - grow successfully if they are grown in a humid atmosphere until the roots have developed

  - use a rooting hormone

  - cover with a clear polythene bag until the roots have developed (maintains moist environment)

  - remove lower leaves to reduce transpiration
• Tissue culture (micropropagation) method


  - small pieces (explants) are cut from plants

  - explant is sterilised

  - explant transferred to agar plate containing nutrients and plant growth substances (hormones)

  - agar plate incubated and explant grown into a callut (lump of cells)

  - small plants grown in glasshouse before being planted outside
• Why are the explants sterilised?


  - to prevent pathogens (harmful bacteria) multiplying and compete for nutrients

  - can bleach explants
• What nutrients might be in agar?

  - magnesium for chlorophyll

  - nitrates for proteins (DNA) and growth

  - glucose for respiration
• Name of a plant growth substance

  Auxin (grows roots and shoots)
• Why are the explants covered during growth?


  - no roots so water cannot be taken up by the plant from the soil
• Cloning animals by nuclear transfer


  - involves replacing the nucleus of an unfertilised egg (haploid) with the nucleus from a different cell (diploid)

  - as the nucleus contains genetic information the egg will grown into a clone of the donor of the nucleus
• How was dolly produced through nuclear transfer?

  - an egg cell was removed from the ovary of a female sheep B, and its nucleus removed (this is called an enucleated cell)

  - the nucleus from an udder cell of a donor sheep A was inserted into the empty egg cell

  - to stimulate the egg cell to divide it is given a small electric shock

  - the fused cell then began to develop (mitosis) using genetic information from the donated DNA

  - before the dividing cells became specialised, the embryo was implanted into the uterus of a surrogate mother sheep C

  
• Genetic engineering


  - genetic engineering is the alter of genes in the ways that we want

  - involves taking a gene or a length of DNA and inserting it into the DNA of another organism like a bacterium so that it produces the protein coded for by the introduced gene
• How are specific species of DNA cut?


  - Specific pieces of DNA or genes are cut by using enzymes isolated from bacteria—> restriction enzymes

  - at the same time a piece of circular DNA called plasmid is removed from a bacterium and cut open by a restriction enzyme

  - the new gene is then inserted into the plasmid by another enzyme called ligase

  - the plasmid is known as a vector

  - the final molecule is known as recombinant DNA (2 species bacterial +human)

  
• How is the recombinant DNA injected into bacterium?

  - sometimes a virus is used as a vector to inject the recombinant DNA into a bacterium

  - the bacteria are grown in fermenters and act like "factories" producing desirable gene products

  - when DNA is transferred from one species to another the resulting individual is transgenic
• Applications of genetic engineering

  - Insulin (hormone required by diabetics) was first produced by recombinant DNA technology

  - drugs like antibiotics or vaccines are made on a large scale

  - also possible to transplant genes from one animal to another and between plants

  - e.g. genes responsible for making proteins in human milk could be transplanted into the DNA of a cow which would produce human milk

  - new strains of plants can be made with resistance to diseases or pesticides, increased nutritional value, increased yield etc

  - the gene for nitrogen-fixation can be isolated from a bacterium and inserted into a wheat plant, and then there would be no need to use fertiliser in soil
• Stem cell

  - Cell that can become any other type of cell

  - undifferentiated cell
• Specialised cell

  - specific structures to carry out its functions
• Differentiation

  - process of forming specialised cells
• Why are embryonic stem cells better than adult cells?

  - embryonic are stem cells which means they are undifferentiated and can become any other type of cell

  - adult cells only turn into a few certain cells
• What is the main source of embryonic stem cells?

  - Unused embryos from IVF

  - umbilical cord
• What is happening when a patient rejects a donated organ?

  - antigens (proteins) on the cells of the donated organ are not recognised by the immune system
• Why will a patient not reject an organ made from their own stem cells?

  - they recognise the antigens