The Production of Cloned Mammals (Edexcel IGCSE Biology)

Cloning Mammals

Spec point — 5.19B · describe the stages in the production of cloned mammals involving the introduction of a diploid nucleus from a mature cell into an enucleated egg cell, illustrated by Dolly the sheep

Adult cell cloning

• Adult cell cloning is achieved in the following way:

  • The nucleus is removed from an unfertilised egg cell, producing an enucleated egg cell
  • The diploid nucleus from a mature adult body cell, such as a skin cell, is inserted into the enucleated egg cell
  • A very small electric shock stimulates the cell to divide (by mitosis) to form an embryo
  • These embryo cells contain the same genetic information as the adult skin cell
  • When the embryo has developed into a ball of cells, it is inserted into the uterus of an adult female (known as the surrogate mother) to continue its development until birth

• This process was used to create the first clone (exact genetic copy) of a mammal in 1996

  • Scientists in Scotland successfully cloned an adult female sheep
  • The clone was called Dolly

Adult cell cloning: the cloning technique used to produce the first cloned mammal, Dolly the sheep

Benefits & risks of cloning table

Cloning to Produce Human Proteins

Spec point — 5.20B · understand how cloned transgenic animals can be used to produce human proteins

• Dolly the sheep was the first cloned mammal produced from an adult cell
• Scientists can produce transgenic animals by inserting a foreign gene into their genome
• The foreign gene can code for a useful protein, which the animal can then produce in its milk, eggs, or blood
• Once a transgenic animal has been created, it can be cloned to produce more animals with the same trait
• Uses of transgenic animals include producing useful proteins for medical purposes, such as proteins to treat diseases in humans