5.19 Mammal Cloning

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.

Dolly the sheep: 
1.  An egg cell was removed from the ovary of an adult female sheep and its nucleus removed. (enucleated)

2. The nucleus from an udder cell of a donor sheep was inserted into the empty egg cell. 

3. The fused cell then began to develop normally, using genetic information from the donated DNA 

4. The cell develops into an embryo by mitosis, and is implanted into the uterus of a foster mother sheep. 

5. Result = lamb born (Dolly) genetically identical to 'parent' sheep. 

OBJ 5.18 Commercial plant growing

Understand how micropropagation can be used to produce commercial quantities of

identical plants (clones) with desirable characteristics


1. Plant has characteristics that are commercial --> desirable --> lots of copies are wanted 

a) sexual reproduction --> variation = loss of quantities. 
2. Cloning technique --> micropropagation --> this gives us many plants of the same quality (same product) 

5.17 Micropropagation - CLONING

Describe the process of micropropagation (tissue culture) in which small pieces of plants (explants) are grown in vitro using nutrient media

Cloning = any procedure that produces genetically identical offspring. 
Micropropagation = a cloning technique(explants) = tips of stems and side shoots 

1. The tips of a stem and side root are teared off the plant under aseptic conditions. 

2. They are then placed in a petri dish agar that contains nutrients and plant hormones to encourage growth. 

3. The explants with shoots are then transferred to another culture medium containing a different balance of plant hormones to encourage root formation. 

4. When the explants have grown roots, they are transferred to greenhouses and transplanted into compost --> they then grow under normal conditions. 

5. These seedlings are genetically identical --> clones. 


Advantages: 

• large numbers can be produced rapidly
• species that are difficult to grow from seeds or cuttings can be propagated 
• can be produced at any time of the year
• large numbers of plants can be stored easily

5.15a Genetically Modified Plants

Evaluate the potential for using genetically modified plants to improve food production(illustrated by plants with improved resistance to pests)

1. Eg: maize 

a) Maize damaged by cork borer larvae --> reducing crop yield by 20%

2.  

a) The existence of a Bacteria called  "BT." It contains a chromosome with a gene, that when switched on it produces "Bt" toxin. 

b) BT toxin kills the cork borer larvae

3. 

a) The DNA from the BT gene is cut with restriction enzymes to isolate the desired gene (BT gene for the toxin)
b) It then is transferred to the cells of the maize plant by a 'gene gun.' 
c) The gene gun fires a tiny golden pellets coated with DNA that contains the BT gene (desired gene)
d) These are then 'fired' directly into young plant tissue
e) The genetically modified tissue can then be grown into new plants 
f) This gives maize the resistance against damage caused by the cork borer  larvae

5.14 Humulin

Understand that large amounts of human insulin can be manufactured from genetically modified bacteria that are grown in a fermenter

1. Bacterial cell transformed by recombinant DNA (with the plasmid DNA combined with the human DNA of the insulin gene.) 

2. A culture of this bacteria (large population) is injected into a fermenter 

Necessities : 

- provide nutrients
- control the temperature  + pH
- control the gases in the fermenting chamber 

Creating  the optimum  temperature for bacterial growth ---> pop will increase + bacteria will manufacture the protein Insulin. 

3. The bacteria will manufacture the insulin protein from the nutrient protein (amino acid) 

4. Then it will be necessary to remove the product --> carry out purification by downstream processing. 

5. The genetically engineered human insulin is called 'Humulin.'

5.13b Hosting recombinant DNA

Describe how plasmids and viruses can act as vectors, which take up pieces of DNA, then

insert this recombinant DNA into other cells.

Vector = transfers the gene eg:into the plasmid 

1. 

• Remove the nucleic acid from the virus to get just the Caspid protein shell 
• the plasmids are taken up by the virus 
• the virus acts as a vector of the recombinant DNA - helping us to transfer the DNA into the host cell
  
  
  
  2. 
• This type of virus = a PHAGE 
• it infects bacterial cells
• the virus is able to attach to cell membrane of the bacteria and insert the recombinant DNA into the host cell. 
• the bacterial cell now contains the recombinant DNA and the human gene for insulin. 
• this combination is known as 'Transgenic' 
  
  

OBJ 5.13a Recombinant DNA5.13b Hosting recombinant DNA

Describe how plasmids and viruses can act as vectors, which take up pieces of DNA, then insert this recombinant DNA into other cells.
Recombinant DNA = a section of DNA is snipped out of the DNA of one species and inserted into the DNA of another the new DNA is called the "Recombinant DNA." 

1. Plasmid = 

• found in bacterial cells 
• small circular ring of DNA 
• don't carry very many genes 

2. Virus = 

• has a protein shell called a Caspid
• contains a nucleic acid (DNA/RNA) 
• (no cytoplasm, no nucleus etc)
  
  
  3.  Human Chromosome 
• (length of DNA) 
• identify a gene --> this gene codes for the protein Insulin (hormone controlling blood sugar levels) 
• the restriction enzyme is selected to cut the DNA (to cut the gene for insulin) 
• the gene is cut --> now isolate the plasmids and cut it with the same srestriction enzyme
• the plasmids are now open in a structure much like a "C"
• the opened up plasmids and the human gene insulin are mixed with a DNA ligase enzyme to create recombinant plasmids (combination of human gene + plasmid)
  
•