DNA profiling 2

DNA profiling 2

Describe the limitations of DNA profiling in relation to the two uses of DNA profiling.

Paternity Test:

The more people tested the lower the statistical probability.

Criminal Investigation:

New profiling technologies can give incorrect results due to cross-contamination of samples.

DNA evidence is easily planted at a crime scene

Other limitations

End of Genetics paper 2

a)     Calculate the difference in consumption of the 6% alcohol solution between the

I)               NPY -/- and NPY +/+ : 3 grams per kilogram weight are consumed per day

II)              NPY – EX and NPY +/+ 2 grams per kilogram weight are consumed per day

b)     NPY -/- consumes more alcohol than NPY +/+ but NPY-EX consumes less than NPY +/+. NPY -/- also consumes more alcohol than NPY-EX. The consumption levels off at a higher concentration for NPY -/- than it does for NPY-EX.

c)     The relationship between NPY levels and alcohol consumption is inversely related.

d)     NPY -/- can regain the reflex fastest, whereas NPY-EX takes the longest. This is because NPY-EX is affected more by alcohol than NPY-/- is.

e)     The hypothesis is not fully supported. There is a small difference in blood levels at 1 hour and 3 hours.

f)      NPY-EX is more affected to alcohol and thus doesn’t prefer it. Unlike NPY -/- which prefers alcohol because it is less sensitive to alcohol and therefore has more of it.

g)      

a.     Homozygous means that there are two identical alleles of the same gene

b.     It has normal levels of NPY

c.      

	NPY+	NPY +
NPY -	NPY +/-	NPY +/-
NPY -	NPY +/-	NPY +/-

100%

1.

a) There is a higher percentage of lectin in all GNA varieties in comparison to Con A varieties by about ten fold.

b) Con A 4 because it has the highest percentage of Aphid and Nematode control.

c) It seems that the higher the lectin content the better aphid control however there does not seem to be a relationship with Nematode control.

d) (5500-3800/5000) x 100 = 34%

e) There is a greater effect of the GM potatoes on protozoa because the percentage difference of the mean mass of protozoa is greater than the nematodes. This is the case for both GNA 2#28 and Con A 31. For example, the percentage difference in mass was 63% and 51% for the flagellates and amoebae but for the nematodes it was only 34%. 

DNA profiling

DNA profiling

      DNA profiling involves the partial sequencing of genomes

• ·       Profiles tend to focus on areas of satellite of junk DNA which vary significantly between individuals (e.g. the repeated sequence of 16 base pairs on the short arm of chromosome 1)
• ·       By sequencing a number of sections a unique genetic fingerprint can be created for an individual.
• ·       Used for: paternity tests and criminal investigations
• ·       By obtaining DNA profiles from the child, mother and potential fathers, paternity can be established.

Gel electrophoresis

• ·       The laboratory technique separates fragments of DNA to identify its origin.
• ·       Restriction enzymes are used to cut the long filaments of DNA into different sized fragments.
• ·       The DNA fragments are placed into small wells in the gel which are aligned along one end.
• ·       The gel is exposed to an electric current that is positive on one side and negative on the other.
• ·       The effect is that the biggest, heaviest and least charged particles do not move easily through the gel so they get stuck very close to the wells they were in at the origin.
• ·       The smallest and most charged particles pass through the gel to the other side with least difficulty.
• ·       Medium sized particles are distributed in between.
• ·       In the end the fragments leave behind a banded pattern of DNA.

Outline the process of DNA profiling (genetic fingerprinting), including ways in which it can be used (6)

• DNA profiling is often used for criminal investigations or for paternity tests. Firstly, a sample of DNA (often satellite DNA) is required through either hair or from a sample of saliva. The Polymerase chain reaction (PCR) amplifies the DNA and it is an automated process that can produce sufficient DNA in 20 cycles. The DNA is cut using restriction enzymes and these fragments are separated in a process known as electrophoresis. By sequencing a number of sections a unique ‘genetic fingerprint’ can be created for an individual.

2a.

i)  Both the males and females are affected so it’s not sex linked.

ii) It’s likely to be dominant because most of the parents seem to have these symptoms of LDL cholesterol concentration in the blood.

b. III-I= fhfh and III-2 FHfh

ii) 50%

c) a high chance

Cloning

What are clones?
A clone is a group of genetically identical organisms or a group of cells derived from a single parent cell.

Ethical Issues
They must be separated into reproductive cloning and therapeutic cloning.
Reproductive cloning = Dolly the sheep. Humans = twins...
Therapeutic cloning involves the isolation of stem cells
Foetal stem cells are often harvested from unused IVF embryos
These have the potential to be of great medical benefit. e.g. healing burns, heart tissue post cardiac arrest, kidney damage

Discuss the ethical arguments for and against the cloning of humans (4)
There are many arguments against the cloning of humans. For example, it's not our role as people to do this and some might say that we are tempting higher powers. It is also a very costly process and the consequences of cloning humans aren't known. Some clones may also show premature aging of have other health problems as a side effect. Some reasons for cloning may also be bad, for example, to replace a deceased family member.

However, there are some benefits to cloning. Cloned embryos can be used for further health research. Twins are also a form of cloning.

Outline a basic technique for gene transfer involving plasmids (5)
Gene transfer involves using restriction endonuclease to remove the plasmid, a circular ring of DNA from the bacteria. This leaves the stick ends at the end of the plasmid which are unattached hydrogen bonds. The donor is cut using the same restriction enzyme so that DNA ligase enzyme can join the sticky ends together. This is known as the recombinant plasmid. The cells are then replicated.

Outline a technique for transferring genes between species (5)
The gene that is required is cut out using restriction endonuclease. The plasmid is cut open with the same restriction enzyme. This gene is inserted into the plasmid using DNA ligase that splices the sticky ends together. This is called a recombinant plasmid. The plasmids are inserted into new host cells suc as bacteria or viruses.

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

• PCR is the cloning of DNA 
• Copies are made and the amount of DNA can be rapidly increased. This is useful if the source of DNA is small.
• Temperature is used instead of enzymes like helicases (95˚C)
• DNA polymerase is thermostable to protect it against the reaction temperatures.
• This is an automated process and can produce sufficient DNA in 20 cycles.
• It is a laboratory technique that is used to solve a simple problem: how to get enough DNA to be able to analyze it. 
• By using PCR forensics experts or research technicians can obtain million of copies of the DNA in just a few hours. 
• Such quantities are large enough to get results from, notably using gel electrophoresis.

Gene Transfer

Gene transfer is the technique of taking a gene out of one organism and placing it in another organism.


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

Cutting and pasting DNA
Restriction enzymes called endonucleases are used to cut out the gene that needs to be transferred. If both the beginning and end of a gene are cut, the gene is released and can be removed from the donor organism.

DNA ligase is used for pasting genes as it recognizes the parts of the sticky ends and attaches them together.

DNA Cloning
A host cell is needed in addition to those two enzymes. Although yeast cells can be used as host cels, E. coli is most popular.  Plasmids are small circular DNA molecules found in bacteria, and can be cut with the same restriction enzyme. This leaves the sticky ends in the plasmid, which are, effectively, unattached hydrogen bonds. The plasmid can be cut at particular sites called the restriction sites. To copy a gene, it has to be glued into a plasmid.

The gene is pasted into the plasmid using DNA ligase. The plasmid is now called a recombinant DBA and it can be used as a vector.

The vector is placed inside the host bacterium and the bacterium is given ideal conditions to grow. This is done by putting it into a bioreactor. This process has been used to make human insulin.

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

Benefits of GMO:

1. Increase yields in regions of food shortage
2. Yields crop with specific dietary requirement such as vitamins and minerals
3. Crops that don't spoil easily
4. Farmers can be in control of what crops or livestock they produce.
5. Multinational companies who make GM plants claim they will enable farmers in developing nations to reduce hunger by using pest-resistant crops or GM plants which require less water.

Harmful effects

1. No one knows the long term effects of GMOs in the wild. Genes from GM plants could be integrated into wild species giving them an unnatural advantage over other species and an ability to take over the habitat.
2. Bt-crops which produce toxins to kill insects could be harmful to humans.
3. Risks for allergies: could be allergic to GM tomatoes.
4. Critics are worried that large portions of the human food supply will be the property of a small number of corporations.
5. High-tech solutios are not necessarily better than simpler solutions. Crop production could be increased by teaching farmers how to use water and natural pest-control systems more efficiently.
6. A proliferation of genetically modified organisms may lead to a decrease in biodiversity.

Rod and Cone Cells

Rod and Cone Cells

E.2 Structure of the Eye

E.4 Neurotransmitters and synapses

 a) Explain how pre-synaptic neurons can affect post-synaptic transmission of impulses (7)

Typically a presynaptic neurone excites a post synaptic neurone – the impulse is transmitted across the synapse. This is called an excitatory synapse. When the action potential reaches the are of the terminal buttons of the pre-synaptic neuron, it causes calcium ions to diffuse into the terminal buttons. Vesicles containing neurotransmitters fuse with the plasma membrane and release them into the synaptic cleft. The neurotransmitters bind with a receptor protein on the postsynaptic neurone membrane, this binding results in an ion channel opening and sodium ions diffusing through this channel. This initiates the action potential to begin moving down the post-synaptic neurone because it has been depolarized (made more positive).

However, some synapses are inhibitory synapses; the release of neurotransmitters into the cleft inhibits an action potential being generated in the post-synaptic neurone. At an inhibitory synapse the release of neurotransmitters into the synaptic cleft triggers the opening of ion channels, which allows Cl- ions to enter the neurone and K+ to leave. This makes the interior of the post-synpatic neurone more negative (hyperpolarised) and therefore less likely to initiate an action potential.

b) Explain the process of synaptic transmission (7)

At the far end of axons are swollen membranous areas called terminal buttons. Within these terminal buttons are many vesicles filled with neurotransmitters.

When an action potential reaches the area of the terminal buttons, it causes calcium ions to diffuse into the terminal buttons. Vesicles containing neurotransmitters fuse with the plasma membrane and releases the neurotransmitters into the synaptic cleft. Neurotransmitters diffuse across the synaptic cleft from the presynaptic neurone to the postsynaptic neurone.

Neurotransmitters bind with a receptor protein on the postsynaptic neurone membrane. This binding results in an ion channel opening and sodium ions diffusing in through this channel. This initiates the action potential to begin moving down the postsynaptic neurone because it’s been depolarized.

The neurotransmitter is degraded and broken into two or more fragments by specific enzymes. They’re then released from the receptor protein. The ion channel closes to sodium ions. The neurotransmitter fragments diffuse back across the synaptic gap to be reassembled into the terminal buttons of the presynaptic neurone.

 

Excitatory drugs

Nicotine
• Nicotine in tobacco products is a stimulant which mimics acetylcholine (Ach). Thus, it acts on the cholinergic synapses of the body and the brain to cause a calming effect. After Ach is received by the receptors, it is broken down by acetylcholinesterase but the enzyme cannot break down the nicotine molecules which bind to the same receptos. This excites the postsynaptic neurone and it begins to fire, releasing a molecule called dopamine. Dopamine gives the feeling of pleasure, a molecule of the ‘reward pathway’ of our breains.

Cocaine

• Dopamine transporters are responsible for removing dopamine molecules from the synaptic cleft after they have done their job
• Cocaine blocks these transporters, leaving dopamine trapped in the synaptic cleft. As a result, dopamine binds again and again to the receptors overstimulating the cell
• Cocaine concentrates in the reward pathway. It's also active in the part of the brain controlling voluntary movements. This is why cocaine abusers are unable to stay still.

Amphetamine
• Stimulates transmission at adrenergic synapses and gives increased energy and alertness. Amphetamine acts by passing directly into the nerve cells which carry dopamine and noraderenaline
• It moves directly into the cesicles of the presynaptic neurone and causes their release into the synaptic cleft. Normally, these neurotransmitters would be broken down by enzymes in the synapse, but amphetamines interefere with the breakdown.
• Thus in the synapse high concentrations of dopamine cause euphoria, and high concentrations of noradrenaline may be responsible for alterness and high energy effect of amphetamines.

Inhibitory Drugs

Benzodiazepine
• Reduces anxiety can also be used against epileptic seizueres.
• Its effect is to modulate the activity of GABA which is the main inhibitory neurotransmitter. When GABA binds to the postsynaptic membrame, it causes Chloride ions to enter the neurone.
• This hyperpolarizes the neurone, and resists firing.
• Benzodiazepine increases the binding of GABA to the receptor and causes the post synaptic neurone to become more hyperpolarized.

Alcohol

• Inhibitory neurotransmitters, called GABA, are active throughout the brain. These neurotransmitters act to control neural activity along many brain pathways. When GABA binds to its receptors, the cell is less likely to fire.
• However, in another area of the brain, another neurotransmitter called glutamate acts as the brain’s general-purpose excitatory neurotransmitter.
• When alcohol enters the brain it delivers a double sedative punch. First, it interacts with GABA receptors to make them even more inhibitory.
• Second, it binds to glutamate receptors, preventing the glutamate from exciting the cell.
• Alcohol particularly affects areas of the brain involved in memory formation, decision-making and impulse control.

Tetrahydrocannabinol (THC)
• Main psychoactive chemical in marijuana.
• Before marijuana enters the system, inhibitory neurotransmitters are active in the synapse. These neurotransmitters inhibit dopamine from being released
• When activated by the body’s own native cannabinoid (called anandamide), cannabinoid receptors turn off the release of inhibitory transmitters. Without inhibition, dopamine can be released.
• THC, the active chemical in marijuana, mimics anandamide and binds to cannabinoid receptors. Inhibition is turned off and dopamine is allowed to squirt into the synapse.
• Anandamide is known to be involved in removing unnecessary short term memories. It is also involved for slowing down movement, making us feel relaxed and calm.
• Unlike THC, anandamide breaks down very quickly in the body. That explains why anandamide doesn’t produce a perpetual natural ‘high’.

THC (Tetrahydrocannabinol) / Marijuana

Marijuana is usually smoked as a cigarette or in a pipe. When someone smokes marijuana, THC rapidly passes from the lungs into the bloodstream, which carries the chemical to the brain and other organs in the body.

THC acts on specific sites in the brain called cannabinoid receptor. They start off a series of cellular reactions that lead to the “high” that users experience when they use the drug. Some brain areas have many cannabinoid receptors while others have few or none. The highest density of cannabinoid receptors are found in parts of the brain that influence pleasure, memory, thinking, concentrating, sensory and time perception and coordinated movement. Marijuana intoxication can caused distorted perceptions impaired coordination, difficulty with thinking and problem solving and problems with learning and memory.

Cocaine

Cocaine is a powerfully addictive central nervous system stimulant. This drug usually makes the user feel euphoric and energetic, but also increases body temperature, blood pressure and heart rate. Users risk heart attacks, respiratory failure, strokes, seizures, abdominal pain and nausea.

Cocaine also causes dopamine release. Cocaine blocks removal of dopamine from the synapse so that it builds up. This leads to over stimulation of the postsynaptic neurone. The synaptic effect of cocaine results from its ability to sustain the level of dopamine in the synapse. Since dopamine is the neurotransmitter in the ‘reward pathway’, the longer it stays in the synapse the better you feel.