IB Biology - 3.5 Biogenetics

Polymerase Chain Reaction

Technique that allows molecular biologists to make many copies of a particular gene

State the role of PCR in labs and investigations

Used to amplify small segments of DNA to use for DNA profiling, recombination, species identification and other research

Identify the cellular process which PCR mimics

DNA replication, profiling, recombination, species identification & other research

State the role of high temperature in PCR

Thermal cycler denatures hydrogen bonds, exposing bases

State the role of complementary base pairing in PCR

Complementary base pairing cycle repeated many times - thousands of copies (DNA polymerase replicates DNA)

Describe why it is called a "chain reaction"

The strands help reseparating - whole process continues to make multiple copies

Two main uses of DNA profiling by electrophoresis

-Determine paternity/relationships as evidence in criminal cases
-Species identification

Two other names for DNA profiling

-DNA fingerprinting
-DNA typing

Gel Electrophoresis

Procedure used to separate and analyze DNA fragments by placing a mixture of DNA fragments at one end of a porous gel and applying an electrical voltage to the gel

How does Gel Electrophoresis work?

1) DNA samples taken
2) PCR amplifies DNA to get a useful amount
3) Restriction enzymes cut DNA fragments of various lengths
4) A fluorescent marker binds to a triplet in the DNA fragments, so that results can be seen
5) Samples are added to a gel electrophoresis chamber at the origin end of the electrophoresis gel
6) Electric current is passed through, pushing the fragments along
* Heavier fragments stay closer to the origin and smaller fragments go further
7) A banding pattern shows up for each DNA sample and can be compared

Role: Restriction Enzymes

Cut DNA fragments at specific base sequences

Role: Gel

Fragments of DNA moved through an electric field

Role: Electric Current

Passed through gel, pushes fragments along

Role: Fluorescent DNA Markers

Bind to triplets of DNA fragments so results can be seen

Human Genome Project

An international collaborative effort to map and sequence the DNA of the entire human genome.

Outline the goals of the Human Genome Project

-Identify all genes in human DNA
-Determine sequences of A,T,C & G that make up human DNA
-Store information in a public database
-Improve tools for data analysis
-Transfer related technologies to private sector
-Address ethical, legal & social issues that may arise from the project

Transgenic Organism

Genetically modified/engineered organism

Give 3 Examples of naturally occurring clones:

-Identical Twins
-Vegetative Propagation in Plants (Asexual Reproduction)
-yeast germes and protozoa (single celled organisms)

Define differentiated nucleus:

A nucleus that is specialized to perform a specific function

Suggest why the differentiated nucleus was taken from an udder cell.

Udder cells are able to be reprogrammed and differentiated to suit a different function

Suggest one reason why Dolly died younger than normal, but of age-related illnesses.

Dolly was cloned from an adult sheep with half of their telomeres; therefore, Dolly was born with half the life span of a normal sheep

Outline the method used to clone Dolly the Sheep

1. Udder cells removed from sheep
2. Cells grown in a culture to turn off their genes
3. Embryos removed from sheep
4. Nuclei removed from embryos
5. Embryos and udder cells fused by electricity to form zygotes
6. Zygotes developed to form embryos
7. Embryos implanted into Sheep 3 (the surrogate mother)
8. Dolly develops and becomes first born clone (identical to sheep 1)

Distinguish between reproductive cloning and therapeutic cloning

-Reproductive: creates an exact whole copy of an already existing mature life form.
-Therapeutic: creates a whole copy of an already existing mature life form but does not allow the cloned embryo to come to full term resulting in birth; produces cells for use in growing replacement organs or for tissue engineering designed to heal or cure disease in human beings.

State some of the medical applications and benefits of therapeutic cloning.

-Stem cells have the capacity to divide and differentiate into any type of human cell
-They can be used to replicate tissues or organs that have been damaged 21.) Discuss the ethical considerations of therapeutic cloning in humans.
-Advantages:
cells can be removed from embryos that have been stopped developing, would have died anyways
cells are removed at a stage when embryos have no nerve cells, can feel no pain
stem cells can be used for therapeutics that save lives and reduce suffering
-Disadvantages:
More embryos may be produces when needed, so some may have to be killed
Stem cells develop into tumor cells
Every embryo is a potential human being, should be given the chance to develop

Suggest why stem-cell programming might mitigate the negative opinions of human therapeutic cloning.

a.) IPS Cells (Induced Pluripotent Stem Cells): adult cells that have been genetically reprogrammed to an embryonic stem cell-like state by being forced to express genes and factors important for maintaining the defining properties of embryonic stem cells.
b.) IPS cells are are genetically modified by the integration of up to four DNA-transcription factors into the adult cell genome.
c.) Benefits:
Are not derived from human embryos Questions 19 + 20 May allow scientists to sidestep other controversial methods, notably cloning (which is both ethically questionable and difficult to do routinely)

Define clone and uses:

Clone: a group of genetically identical organisms or a group of genetically identical cells derived from a single parent cell Why Use Cloning? Cloning is very useful if an organism has a desirable combination of characteristics and more organisms with the same characteristic are wanted (known as reproductive cloning).

Advantages and disadvantages of cloning:

Advantages: Every human embryo is a potential human being, which should be given the chance to develop
More embryos may be produced than are needed, so some may have to be killed
There is a danger of embryonic stem cells developing into tumor cells Techniques are being developed to create human embryos, from which embryonic stem cells can be obtained for medical use. These stem cells have the capacity to divide and differentiate into any types of human cell. They could be used to replace tissues or even organs that have become damaged or lost in a patient. There are many ethical issues involved, which has resulted in therapeutic cloning being banned in various countries.

What is the process used to amplify small amounts of DNA

polymarse chain reaction

What is the role of E. Coli in the HGP?

act as copiers

Outline gene transfer:

-mrna is extracted
-dna copies are made
-selected plasmid is cute using restiction enzymes
-ligase makes sugar phosphate backbone
-insterted into host cell

Role of restriction enzymes in gene transfer:

cut selected plasmid

Role of Ligase in gene transfer:

makes sugar phosphate backbone

Role of vector in gene transfer:

carries foreign genetic material to another cell