Biology 4.4

• Concerns about Genetic engineering:
• Variation


  The differences of organisms of the same species. Variation can be genetic, environmental or a combination of both.
• Genetic variation


  • Caused by the inheritance of DNA from parents to form a child. Since a parent only gives 23 Chromosomes, the child may look like their mother or father but will not be genetically identical.
• Genetic variation


  • Blood type, skin and eye colour, shape of ears, nose and hair colour.
• Genetic variation cannot be altered by environmental factors.
• Environmental variation


  • Some variation can be affected by environmental and genetic factors. Height and weight are affected by the living conditions an organism develops in. This cannot be passed onto the next generation and may change due to its environment even if it has genetic origins.
• Environmental variation


  • Scars, accent, piercings, muscularity.
• Phenotypic variation


  • Some variation can be affected by environmental and genetic factors. Height and weight are affected by both. For example, someone may have a gene to be tall yet need proper nutrition to reach that height during childhood.
• Types of variation


  • Continuous - a continuous range with no categories
  • Discontinuous - fixed categories with no ranges
• A continuous graph will have a bell shaped curve with the highest result in the middle and the others fanning around it.
• A discontinuous graph will have no pattern, with categories a person will sit into, no middle ground. Normal bar chart.
• Asexual reproduction


  Only one parent is needed, meaning the offspring will be genetically identical to the parent. There is no fusion of gametes, so there is no mix of genetic material.
• Asexual reproduction


  • Bacteria, fungi, some plants like strawberry plants and bananas.
• Sexual reproduction


  Two parents are needed, one male and one female, meaning the offspring will be genetically different, having some similarities with each parent. There is a fusion of gametes that forms a zygote and causes a mix of genetic material.
• Mutations rarely happen during asexual reproduction, they happen by mistake meaning they all thrive in the same environment as the parent, but if a change happens all are affected.
• Mutations commonly happen during sexual reproduction, they happen during the reproduction of a child these allow the offspring to be born with new or enhanced features that allow them to thrive in their environment, even if there are changes.
• Evolution


  The process by which species have gradually changed and developed from earlier forms over a long period of time. This has a mechanism called Natural selection which is a theory proposed by Charles Darwin and Alfred Russel Wallace in 1858.
• Principles of evolution by Natural Selection


  • All species of living evolved from simple life forms over a period of time.
  • The Earth is about 4.5 million years old and there is scientific evidence that suggests life began on Earth more than 13 billion years ago.
  • All individuals of a species vary due to variation and mutation.
  • In every population more offspring are produced then can survive, known as over production. This leads to competition between young organisms for survival.
  • Individuals born with characteristics that benefit their survival are more likely to live longer, known as survival of the fittest.
  • Individuals born with poor characteristics are less likely to adapt to their environment and more likely to die, meaning their genes will be lost.
  • Individuals with characteristics that allow them to adapt will pass their genes down to the next generation. There will be variation but the characteristics from the parents that benefit the young's survival will be present.
  • This will result in the whole species gaining the improved characteristic and losing the bad ones.
• Evolution evidence


  • Antibiotic resistance in bacteria
  • Warfarin resistance in rats
• Mutation


  A change in a gene or chromosome. It's rare and random in the genetic material, some can be inherited.
• Mutations have a greater chance of happening when exposed to carcinogens, radiation; this includes gamma rays, x-rays, and ultraviolet rays. Chemical exposure can increase the rate too.
• Most mutations cause little changes or have no affect on the phenotype.
• Mutations sometimes can be beneficial, however they can sometimes be harmful too.
• Mutations in the sex cells (gametes) will be passed on, mutations in the body cells will not.
• Cystic Fibrosis


  An inherited disease, a negative mutation, that creates a thick, sticky mucus which clogs the lungs and digestive system (pancreas), causing problems with breathing and digesting food.
• Cystic Fibrosis genotype


  Caused by a pair (homozygous) of recessive alleles, (ff) if they have a dominant allele they will not develop cystic fibrosis. If someone has the gene for cystic fibrosis but doesn't suffer, they are known as carriers with one recessive allele.
• Gene therapy


  Replacing the diseased allele (cystic fibrosis) with a normal allele of the same gene. Special enzymes are used to cut out the normal allele, make many copies of it, and put the copies of the normal allele into the cells of a person who has the inherited disease/Known as "switching off" the 'harmful allele.
• Gene therapy does not always work successfully and research is ongoing.
• Problems around Gene therapy


  • The alleles may not go into every target cell.
  • The alleles may join with the chromosomes in random places, so they don't work properly.
  • Treated cells may be replaced naturally by the patient's own untreated cells.
• Some religious groups believe that humans should not attempt to alter the genes of living organisms. The process is very expensive, and may take funds from other areas of research that could save more people. It offers hope for a person to live a normal life, but it is not a guarantee.