Study resource
Natural selection and genetic modification revision notes
Review revision notes for Natural selection and genetic modification in Edexcel Biology.
At a glance
revision notes
Resource type
Topic
Natural selection and genetic modification
Revision notes
Stages of Genetic Engineering Revision Notes
Restriction Enzymes and Sticky Ends
Restriction enzymes act like molecular scissors, cutting DNA at defined sites. Many create 'sticky ends,' which are single-stranded overhangs. These sticky ends allow DNA fragments from different sources, cut by the same enzyme, to join together due to their complementary bases.
Vectors and the Role of Ligase
Vectors (like plasmids or certain viruses) are DNA molecules used to transport genes into new cells. After restriction enzymes cut both the vector and the desired gene to make matching sticky ends, DNA ligase is added to form covalent bonds and permanently join the gene into the vector, producing recombinant DNA.
Understanding Tissue Culture Revision Notes
The Process of Tissue Culture
Tissue culture involves taking a small piece of tissue (explant) from a parent organism. This explant is sterilised to prevent contamination and then placed in a sterile, nutrient-rich growth medium. The medium contains essential nutrients, sugars, and growth hormones. Under suitable environmental conditions (temperature, light), the cells in the explant divide and grow, eventually forming an undifferentiated mass of cells called a callus. This callus can then be manipulated by altering the hormone balance in the medium to stimulate the development of roots and shoots, eventually leading to a complete plantlet or specific cell lines.
Advantages of Tissue Culture
Tissue culture offers numerous benefits. In plant breeding, it enables the rapid production of many clones from a single parent plant, ensuring genetic uniformity and desired traits. It's crucial for propagating rare or endangered species and producing disease-free plants, as meristem tissue (often used as explant) is typically free of viruses. For medical research, tissue culture allows for drug screening without animal testing, culturing cells for vaccine production, and studying disease mechanisms in controlled environments. It also supports the production of therapeutic proteins and gene therapy research. The ability to grow large numbers of identical cells or organisms under controlled conditions makes it invaluable.
Related topics