Genetic engineering and biotechnology

Topic 4.4

Assessment statements

4.4.1 Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA.

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

4.4.3 State that gel electrophoresis of DNA is used in DNA profiling.4.4.4 Describe the application of DNA profiling to determine paternity and also in

forensic investigations.4.4.5 Analyse DNA profiles to draw conclusions about paternity or forensic

investigations.4.4.6 Outline three outcomes of the sequencing of the complete human genome.4.4.7 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.

4.4.8 Outline a basic technique used for gene transfer involving plasmids, a host cell (bacterium, yeast or other cell), restriction enzymes (endonucleases) and DNA ligase.

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

4.4.10 Discuss the potential benefits and possible harmful effects of one example of genetic modification.

4.4.11 Define clone.4.4.12 Outline a technique for cloning using differentiated animal cells.4.4.13 Discuss the ethical issues of therapeutic cloning in humans.

Polymerase chain reaction (PCR)

• Laboratory technique which takes a very small quantity of DNA and copies all the nucleic acids in it to make millions of copies of the DNA

• Way to ensure that enough DNA for analysis can be generated

Gel electrophoresis

• Laboratory technique used to separate fragments of DNA in an effort to identify its origin

• Enzymes used to chop up DNA strands into fragments

• Fragments are placed into small wells in the gel• Gel is exposed to an electric current• Heaviest, largest and least charged particles do

not move easily through the gel• Smallest, least massive and most charged

particles pass through the gel to the other side easily

• Intermediate particles are distributed in between• In the end, the fragments leave a banded pattern

of DNA

DNA profiling

• Process of matching an unknown sample of DNA with a known sample to see if they correspond

• Referred to as DNA fingerprinting• If, after separation by gel electrophoresis,

the pattern of bands formed by two samples of DNA fragments are identical, it means that both came from the same individual

• If the patterns are similar, it means that the two individuals are most probably related

Applications of DNA profiling

• Paternity

• Match suspects

• Studies of ecosystems– Social relationships– Migrating patterns– Nesting habits

• Credibility to evolution

TOK

• How would you feel if you were to find out from DNA profiling that your father was not your biological father?

• What effect would such a result have on the relationships between siblings or between spouses?

• What kind of emotions might someone feel after spending 18 years in prison, and then being freed thanks to a DNA test?

The Human Genome Project

• 1990 – 2003

• Determined order of all the bases

• Working now to decipher which sequences represent which genes and which genes do what

• Can be useful in synthesizing beneficial molecules as medical treatment

TOK

• What does the sentence, “We are all the same; we are all different,” mean?

• Can one genetic group be considered genetically superior to another?

• What has our history taught us?• http://www.blackgenocide.org/abortion.html• Why is abortion rates higher among

African-Americans?• http://www.blackgenocide.org/black.html

Gene transfer

• Technique of taking a gene out of one organism (donor) and placing it in another organism (host)

• Ex. host tomatoes more resistant to cold and frost due to donor DNA from a fish

• Proteins used by fish to resist icy temp. of arctic waters are now produced by the modified tomato

• Would strict vegetarians be able to eat a tomato which has a fish gene in it?

• What happens to local ecosystems which rely on insects that may be killed by Bt crops?

Cutting and pasting DNA

• ‘scissors’ made from enzymes• Restriction enzymes called endonucleases

find and recognize a specific sequence of base pairs along the DNA molecule

• Sets of four or six pairs• Gene is cut out and released• Can then be removed from the donor

organism• DNA ligase pastes the genes to the sticky

ends in a particular portion of the DNA sequence

Copying DNA (DNA cloning)

• Most of the genetic info for E. coli is in the single chromosome

• Some DNA is found in plasmids

• Plasmids are small circles of extra copies of DNA floating around inside the cells cytoplasm

• To copy a gene, it must be glued into a plasmid

Steps of copying DNA

1. Plasmid is removed from host cell and cut using a restriction endonuclease

2. Gene to be copied is placed inside the open plasmid using DNA ligase (a.k.a. gene splicing)

3. Recombinant plasmid is used as a vector4. Vector is placed inside host bacterium5. Bacterium allowed to grow and proliferate6. Bacterium expresses the gene and

synthesizes whatever protein the gene codes for

• Used to make human insulin

Genetically modified organisms (GMOs)

• Organisms that has had an artificial genetic change

• Organisms produced to be more competitive in food production

Transgenic plants

• Undesirable gene removed• Desirable gene is put in its place• New gene is just added• Applications:

– Delay ripening– Tolerate high salinity– Produce beta carotene

• Could GM plants help solve world hunger?

Transgenic animals

• Used to produce a substance which can be used in medical treatment

• Examples:– Production of factor IX (protein needed

for blood clotting) – Resistance to parasites– Pre-dyed wool– Show dogs– Faster racehorses

Benefits, promises, and hopes for the future

• GM crops will help farmers by improving food production

• Fewer chemical pesticides will be needed

• Production of rare proteins for medications could be less costly

• Greater control over crop or livestock production

• Lower need for water

Harmful effects, dangers, and fears

• Effect on ecosystems• Genes could cross species• Toxins to kill insects harmful to

humans• Allergies• Food supply property of small number

of corporations• May be simpler solutions• Decrease in biodiversity

Clones and cloning

• Clone – group of genetically identical organisms or a group of cells artificially derived from a single parent

• Fertilized eggs do not differentiate until after dividing many times

• It was once thought that once differentiated, the cell could not be used to produce a clone

• In 1996, a sheep named Dolly was born• First clone whose genetic material did not

originate from an egg cell

How Dolly was produced

1. Somatic cell from donor sheep udder was collected and cultured; nucleus removed

2. Unfertilized egg collected from another sheep; nucleus removed

3. Using a zap of electrical current, the egg cell and the nucleus from the cultured somatic cell were fused together

4. New cell developed in vitro and started to form an embryo

5. Embryo placed in the womb of a surrogate mother sheep

6. Embryo developed normally

7. Dolly was born and presented as a clone of the original donor sheep

• Known as reproductive cloning

Cloning using undifferentiated cells

• Therapeutic cloning involves the copying of cells, not an entire individual

• Aim is to develop cells which have not yet gone through differentiation

• Involves embryonic stem cells

Ethical issues surrounding therapeutic cloning

• Is it ethically acceptable to generate a new human embryo for the sole purpose of medical research?

• Thanks to stem cell research may be able to:– Grow skin to repair a serious burn– Grow new heart muscle– Grow new kidney tissue to rebuild a

failing kidney