Genetic Enhancement

Genetic enhancement is a controversial application of molecular genetics that aims to create larger and healthier plants and animals, mainly for human consumption. To take one example of many, through genetic enhancement, it is possible to produce larger poultry birds such as chicken that possess a greater amount of meat. One method by which genetically enhanced chickens can be produced is demonstrated here. The extent to which domestic chickens grow is partially determined by the number of growth hormone receptors found on the surface of their cells during the stages of early development. As shown, these receptors bind to growth hormone molecules, depicted here as yellow pieces filling the gaps in the membrane of this fertilized chicken egg cell. By artificially increasing the number of growth hormone receptors found on embryonic chicken cells, researchers can produce larger adult chickens. To accomplish this, an ordinary chicken egg is first opened, exposing the embryo within. Germ cells, which develop into sperm and egg cells later in life, are then removed from the embryo and cultured under special laboratory conditions. Many copies of growth hormone receptor genes are inserted into the DNA of each germ cell by homologous recombination. The embryo is then exposed to radioactivity to kill any naturally occurring germ cells that remain, and the recombinant germ cells that contain multiple copies of the growth hormone receptor gene are implanted. The chick that hatches from this egg will grow to the same adult size as an ordinary chicken, but because its egg or sperm cells will have developed from enhanced germ cells, they will contain more copies of the growth hormone receptor gene than usual. Therefore, when the chicken reproduces, it will pass on these extra copies of the gene on to its offspring, which as a result will produce more growth hormone receptors on their cells than ordinary chickens. The increased number of receptors allow more growth hormone molecules to bind to the cells than usual, as shown, which promotes a higher rate of growth among the young chickens than would occur normally. The adult birds that develop from such enhancement techniques are therefore larger than usual, and contain a greater amount of meat for market sale. Although debate continues to arise regarding different aspects of genetic enhancement, this technology may prove very useful, especially for increasing the food supply in third world nations.

Question 1: What is genetic enhancement?
  1. A way in which genes can be made bigger.
  2. A molecular technique used to create larger and healthier plants and animals.
  3. A way in which genes can be made stronger.
  4. A way in which genes can be magnified so they can be visualized.


Answer 1 Answer – (b) A molecular technique used to create larger and healthier plants and animals.

Question 2: ______________ receptors on the surface of animal cells determine the growth of domestic animals.
  1. DNA
  2. Growth hormone
  3. RNA
  4. Mechanical


Answer 2 Answer – (b) Growth hormone

Question 3: Research can lead to production of larger domestic animals by _______________.
  1. breeding them in cages in laboratories and giving them more food
  2. selecting large wild animals and domesticating them
  3. artificially decreasing the number of growth hormone receptors found on embryonic chicken cells
  4. artificially increasing the number of growth hormone receptors found on embryonic chicken cells


Answer 3 Answer – (d) artificially increasing the number of growth hormone receptors found on embryonic chicken cells

Question 4: Copies of growth hormone receptor genes are inserted into the DNA of each germ cell by _______________________.
  1. transferal
  2. homologous recombination
  3. transcription
  4. recombinational insertion


Answer 4 Answer: (c) homologous recombination.