Causes of variation

• State 3 examples of genetic variation in humans. 

  blood group, skin colour and natural eye colour.
• Is Biological sex an inherited variation?

  Yes
• State the factors that can affect the characteristics of animal and plant species

  • Climate
  • Diet
  • Accidents
  • Culture
  • Lifestyle
• State examples of 3 features that show environmental variation

  • Scars
  • Language and accent
  • Flower colour in hydrangeas (Produce blue flowers in acidic soil and pink flowers in alkaline soil)
• Define 'Natural Selection'

  A process where organisms that are better adapted to an environment will survive and have more offspring, passing on their genes to future generations
• State the 4 stages of Selective Breeding

  1. Choose the characteristics of a specific organism
  2. Choose parents that show these characteristics from a mixed population and are then bred together.
  3. Choose the offspring with the best desired characteristics to produce the next generation
  4. Repeat the process over many generations until all offspring show the desired characteristics
• State the 3 desired characteristics in plants.

  • Disease resistance in food crops
  • Wheat plants that produce lots of grain
  • Large or unusual flowers
• State the 3 desired characteristics in Animals

  • Animals that produce lots of milk or meat
  • Chickens that lay large eggs
  • Domestic dogs that have a gentle nature
• State 2 advantages of selective breeding:

  • New varieties may be economically important, by producing more/better quality food
  • Animals can be selected that cannot cause harm (e.g Cattles without Horns)
• State 2 disadvantages of selective breeding

  • Reduces genetic variation which can lead to attack by specific insects or disease
  • Can create physical problems in specific organisms
• Define 'Genetic Engineering'

  Modifying the genome of an organism by introducing a gene from another organism to result in a desired characteristic
• State 4 the 4 steps of genetic engineering

  1. Select the desired characteristic
  2. The gene responsible for the characteristic is cut out of the chromosome
  3. The gene is transferred and inserted into another organism
  4. Replication of the modified organism
• State one ethical reason of being against genetic engineering

  People may find it wrong to create new life forms or to move genes between different species
• State a risk of genetically modified crops (food)

  GM food might contain a substance that causes an allergic reaction or harm
• State the 3 steps of genetic engineering

  1. Enzymes are used to isolate the gene which is inserted into a vector (e.g. Bacterial plasmid or virus)
  2. The vector inserts the gene into required cells
  3. The genes are transferred to animal, plant or microorganism cells during early development. This allows them to develop with the desired characteristics
• State 2 uses of genetic engineering

  • Used in agriculture such as improving the yields of important economic crops
  • Used in the medical field to produce insulin which can be used for treating diabetes
• State 2 advantages of genetic engineering

  • Improves crop yields/crop quality which can be important in developing countries, reducing hunger around the world.
  • Introduces herbicide resistance, resulting in less herbicides being used as weeds are quickly and selectively killed
• State 2 disadvantages of genetic engineering

  • Pollen produced by the plants could be toxic and harm insects hat transfer it between plants
  • Can be harmful to human health
• State the stages of IVF

  • Mother is given LH and FSH to stimulate the maturation of eggs
  • The eggs are collected from the mother and fertilized by sperm from a father in a dish in the laboratory
  • The fertilized eggs develop into embryos
  • One or two embryos are inserted into the mother's uterus