Biotechnology

Question 1

Outline the use of polymerase chain reaction to copy and amplify minute quantities of DNA.

Answer 1

• used to copy and amplify minute quantities of DNA
• useful when small amount of DNA available but large amount required
• DNA from blood, semen, tissues
• PCR requires high temperature and DNA polymerase enzyme

Question 2

State that, in gel electrophoresis, fragments of DNA move in an electric field and are separated according to their size.

Answer 2

In gel electrophoresis, fragments of DNA move in an electrical field and are separated according to their size.

Question 3

State that gel electrophoresis of DNA is used in DNA profiling.

Answer 3

Gel electrophoresis of DNA is used in DNA profiling.

Question 4

Describe the application of DNA profiling to determine paternity and also in forensic investigations.

Answer 4

• organisms have short sequences of bases (repeated many times)
  o satellite DNA
  o vary in length from person to person
• DNA copied using PCR, then cut up into small fragments using restriction enzymes
• Gel electrophoresis separates fragmented pieces of DNA according to size + charge
• gives pattern of bands on gel which is unlikely to be the same for individuals
•  DNA profiling
• used to determine paternity and in forensic investigations to gain evidence

Question 5

Analyse DNA profiles to draw conclusions about paternity or forensic investigations.

Answer 5

1. easier to study how genes influence human development
2. helps identify genetic diseases
3. allows production of new drugs based on DNA sequences of genes or structure of proteins coded
4. give information on origins, evolution and migration of humans

Question 6

State that, when genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.

Answer 6

When genes are transferred between species, the amino acid sequence of polypeptides translated from them is unchanged because the genetic code is universal.

Question 7

Outline a basic technique used for gene transfer involving plasmids, a host cell, restriction enzymes and DNA ligase.

Answer 7

• human gene coding for insulin can be inserted into plasmid
• this plasmid then inserted into host cell such as a bacterium
• bacterium synthesises insulin which can be collected and used
• mRNA coding for insulin extracted from human pancreatic cell
• DNA copies made using enzyme reverse transcriptase
• these DNA copies given extra guanine nucleotides to create sticky ends
• selected plasmid cut using restriction enzymes -> cut DNA into specific base sequence
• extra cytosine nucleotides added to create sticky ends
• then we have plasmid and gene ready
  o get mixed together
• both will link by complementary base paring (CG)
• DNA ligase used to make sugar phosphate bonds
• plasmids with human insulin gene mixed with host cells (bacterium)
• bacterium takes in plasmid and starts producing insulin
  o collected & purified

Question 8

State two examples of the current uses of genetically modified crops or animals.

Answer 8

1. transfer of a gene for factor IX which is blood clotting factor from humans to sheep
   a. factor IX produced in sheep’s milk
2. transfer of gene giving resistance to herbicide glyphosate from bacterium to crops
   a. crop plants can be sprayed with herbicide but not be affected

Question 9

Define clone.

Answer 9

A group of genetically identical organisms or a group of genetically identical cells derived from a single parent cell.

Question 10

Outline a technique for cloning using differentiated animal cells.

Answer 10

• Dolly the sheep
• taking udder cells from donor sheep
• donor cells cultured in a low nutrient medium
  o genes switch off, becoming dormant
• unfertilized egg taken from another sheep
  o nucleus of egg removed (micropipette)
  o egg cells fused with udder cells (pulse of electricity)
• fused cells developed like normal zygotes and became embryos
• embryos implanted into another sheep (surrogate mother)