Genetics

• What is variation within a population?

  Differences in the characteristics of individuals in a population.
• Genes determine the phenotype of an organism - true or false?


  False - the environment also plays a role.
• State three causes of variation in a population.

  Variation may be due to differences in the genes inherited (genetic causes), the conditions in which organisms develop (environmental causes), or a combination of both genes and environment.
• Within a population, there is normally very little genetic variationb- true or false?

  False.
• What causes variation within a population?

  Mutations.
• Define mutation.


  A mutation is a random and spontaneous change in the DNA that makes up a gene.
• What effect will most genetic mutations have?

  No effect.
• List some variation due to genetic causes.

  Blood group.

  Skin colour.

  Natural eye colour.

  Nose shape.

  Biological sex.

  Dimples.

  Lobed or lobeless ear.
• List some variation due to environment causes.

  Scars.

  Language and accent.

  Flower colour in hydrangeas as these plants produce blue flowers in acidic soil and pink flowers in alkaline soil.
• List some variation due to both environmental and genetic causes.


  Height.
• What is selective breeding?

  Selective breeding (artificial selection) is the process by which humans breed plants and animals for particular genetic characteristics.
• Describe the process of selective breeding.

  Selective breeding takes place over many generations. These are the main steps for both plants and animals:

  Select/decide which desired characteristics are important enough to select.

  Choose parents that show characteristics from a mixed population. They are bred together.

  Choose the best offspring with the desired characteristics to produce the next generation.

  Repeat the process continuously over many generations, until all the offspring show the desired characteristics.
• What characteristics are animals selectively bred for?

  Animals which produce more meat or milk.

  Chickens that lay large eggs.

  Domestic dogs with a gentle nature.
• What characteristics are plants and crops selectively bred for?

  Disease resistance in food crops.

  Wheat plants that produce lots of grain.

  Large or unusual flowers.
• What are the risks associated with selective breeding?

  Selective breeding can lead to 'inbreeding' where some breeds are particularly prone to disease or inherited defects.
• What are the benefits of selective breeding?

  Benefits of selective breeding include:

  New varieties may be economically important, by producing more or better-quality food.

  Animals can be selected that cannot cause harm, for example cattle without horns.
• State a drawback of selective breeding?

  Inbreeding - some breeds are prone to disease or inherited defects (e.g. some pugs have breathing problems).
• What does the theory of evolution state?

  The theory of evolution states that all species of living things have evolved from simple life forms that first developed more than three billion years ago.
• What is evolution?


  A change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species.
• How does evolution occur?

  Through the process of natural selection.
• Define 'natural selection'.


  Organisms that have characteristics best suited to their environment, survive and reproduce, passing on their genes.
• Define 'species'.


  Organisms that can interbreed to produce fertile offspring.
• Name the person who first discovered inherited characteristics are determined by 'units' passed on unchanged.

  Gregor Mendel.
• Why were Mendel's ideas of inheritance not accepted during his time?

  As chromosomes were not discovered/seen yet.
• Name the person who proposed the theory of evolution.

  Charles Darwin.
• Name the person who suggested changes that occur in an organism during its lifetime can be inherited.

  (Jean-Baptiste) Lamarck.
• State three reasons why Darwin's ideas were only slowly accepted.

  Conflict with the wild belief that god made all living things.

  Insufficient evidence.

  No mechanism to explain variation and inheritance.
• Who worked with Darwin to develop the theory of evolution?

  Alfred Russel Wallace.
• Apart from evolution, what are two other studies Wallace worked on?

  Warning colouration in animals + Theory of speciation.
• What is speciation?


  The process by which two species evolve from a single original species by natural selection.
• What is antibiotic resistance?

  Bacteria becoming resistant means it cannot be killed by a certain antibiotic.
• What causes antibiotic resistance?

  Random mutations in bacteria/Bacteria sharing resistant genes.
• Describe the steps in which a bacteria strain develops resistance to an antibiotic.

  Mutation occurs in an individual bacterium within a population.

  It survives and reproduces rapidly, making more bacteria with its resistant gene.

  Overtime, all bacteria within the population have that gene.
• Why can bacteria evolve quicker than other organisms.

  Because bacteria can reproduce at a quick rate.
• Suggest 3 methods to prevent and slow down the development of antibiotic-resistant strains.

  Do not overuse antibiotics.

  Patients finish antibiotics course every time.

  Restrict agricultural use of antibiotics.
• Why must patients finish their course of antibiotics every time?

  To ensure all bacteria are killed by the antibiotic, so none can survive to mutate and develop resistance.
• Suggest 3 ways in which a hospital can reduce the spread of antibiotic-resistant strains.

  Only use antibiotics if really needed.

  Use strain-specific antibiotics.

  Maintain high hygiene standards (e.g. wash hands between patient visits).

  Isolate patients infected with resistant strain.

  Visitors wash hands as they enter and leave.
• Why is it difficult to develop new antibiotics to combat the appearance of new antibiotic-resistant strains of bacteria?

  The development of new antibiotics is expensive and slow (won't be able to keep up).
• Define the process of genetic engineering.


  Genetic engineering is the process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic.
• Define genetically modified (GM) crops.


  Crops that have their genes modified are called genetically modified (GM) crops. GM crops include ones that are resistant to insects or to herbicides. GM crops generally show increased yield.