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Il portfolio è ricco di materiale, la lingua è perfettamente controllata e il lessico è corretto. Lodevole l'impegno, c'è solo un errore, (garanzia di autenticità).

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LAB EXPERIENCE WITH THE "GOLINELLI FOUNDATION"

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This is my Word Cloud image.

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An example:

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The human genome is full of repeated DNA sequences. These repeated sequences come in various sizes and are classified according to the length of the core repeat units, the number of contiguous repeat units, and/or the overall length of the repeat region. DNA regions with short repeat units (usually 2-6 bp in length) are called Short Tandem Repeats (STR). STRs are found surrounding the chromosomal centromere (the structural center of the chromosomes).
STR analysis measures the exact number of repeating units. This method differs from restriction fragment length polymorphism analysis (RFLP) since STR analysis does not cut the DNA with restriction enzymes. Instead, probes are attached to desired regions on the DNA, and a polymerase chain reaction (PCR) is employed to discover the lengths of the short tandem repeats.

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A palindromic sequence is a sequence made up of nucleic acids within double helix of DNA and/or RNA that is the same when read from 5’ to 3’ on one strand and 3’ to 5’ on the other, complementary, strand. It is also known as a palindrome or an inverted-reverse sequence.

The pairing of nucleotides within the DNA double-helix is complementary which consist of Adenine (A) pairing with either Thymine (T) in DNA or Uracil (U) in RNA, while Cytosine (C) pairs with Guanine (G). So if a sequence is palindromic, the nucleotide sequence of one strand would be the same as its reverse complementary strand. An example of a palindromic sequence is 5’-GGATCC-3’, which has a complementary strand, 3’-CCTAGG-5’.

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1. Transfer 3 microliters of DNA from the stock microtubes called C-1-2-3 to your own corresponding ones.
2. Add 17 microliters of restriction enzyme to each microtube.
3. Mix each microtube well.
4. Put the tubes into the centrifuge for 30 seconds at 8000 rpm.
5. Move the tubes into the rack.
6. Put the rack into the incubator for 30 minutes.
7. Add 4 microliters of loading dye (like xylene cyanol or bromophenol blue)  to each tube.
8. Load 20 microliters of each sample (C-1-2-3) into 4 wells of the gel. Remember to respect the loading sequence C-1-2-3.
9. Close the lid of the chamber.
10. Insert the plug in the power supply.
11. Set the Power Supply to 90 Volt for 35 minutes.
12. Start electrophoresis.
13. Stop the electrophoresis and unplug the power supply.
14. Transfer your gel onto a transilluminator.
15. Turn the transilluminator on. You should be able to discover the culprit.

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Purpose:
Make a DNA profiling.

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Theme:
What do effect more gel electrophoresis results?
Answer:
1. voltage applied to the electrophoretic cell. The higher the voltage, the faster the DNA moves. But voltage is limited by the fact that it heats and ultimately causes the gel to melt.
High voltages also decrease the resolution (above about 5 to 8 V/cm)
2. buffer solution pH. The buffer is needed to maintain the pH of the DNA solution at close to neutral level because if it can become acidic through electrolysis. The electrical currents caused by the electrodes can cause water molecules to dissociate and release H+ ions. These H+ ions can compromise the experiment if they are allowed to combine with the negatively charged DNA. Negatively charged DNA can become neutral if the H+ ions are interfering. If this happens, there is no more pull from the electrodes and the electrophoresis ceases to work.
3. agarose gel concentration. Agarose gel electrophoresis can be used for the separation of DNA fragments ranging from 50 base pair to several megabases (millions of bases) using specialized apparatus. Increasing the agarose concentration of a gel reduces
the migration speed and enables separation of smaller DNA molecules. The distance between DNA bands of a given length is determined by the percent agarose in the gel.
4. DNA fragments lenghts. The length of the DNA molecule is the most important factor, because smaller molecules travel farther.
(5. presence of bubbiesvin bubbles in the gel. )

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UV LAMP

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THERMAL BATH

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POWER SUPPLY

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CONIC FLASK

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GRADUATED CYLINDER

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COMB

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MICROTUBE (with a CAP)

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SPONGE (with four different microtubes C-1-2-3)

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CENTRIFUGE (with a LID and a ROTATOR)

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GEL TRAY (with WELLS, a GEL SHEET and a TBE SOLUTION)

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MICROPIPETTE

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https://www.thinglink.com/scene/869527675075559424

Touching on the link, it will open my interactive image (the one below) made with the program Thinglink.com

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DNA FINGERPRINTING EXPERIMENT'S EQUIPMENT: THE MICROPIPETTE

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View the interactive image by Anna Paltrinieri

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WHAT ROLE DOES DNA EVIDENCE PLAY IN SOLVING CRIMES?

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WHAT ROLE DOES DNA EVIDENCE PLAY IN SOLVING CRIMES?

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Why has DNA received a  lot of media attention?
DNA has received a lot of media attention because it has a fantastic power of discrimination: when you’ve run a genotype and you compare it back to someone, the random match probability of that particular profile is usually in the billions or trillions to one.
How long has DNA  been used to identify people?
DNA has been used to identify people since basically the mid-eighties, but now labs are using a different type of technology.
The techniques used nowadays are more sensitive. How much DNA is needed to do a test?
Before these more sensitive techniques, you may have needed fifty nanograms or a microgram of DNA and now you're down to less than a nanogram of DNA. So you need less and less DNA to do this.
How many cells are needed to get a full profile?
It takes a vanishingly small amount of DNA to get a full profile.
For example, from a handle object where the perpetrator left three or four cells behind, you can still get a full profile off of that.
In what conditions must the exhibit be kept?
It's important that the exhibits are bone dry and if you can't dry them, if they are pieces of tissue, you freeze them.
How long does DNA last if taken in good conditions?
If taken in good conditions, DNA will last essentially forever.

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What is the basic principle of gel electrophoresis?
Gel electrophoresis separates DNA fragments by size in a solid support medium (an agarose gel).  Electrophoresis uses an electrical field to move the negatively charged DNA through an agarose gel matrix toward a positive electrode. Shorter DNA fragments migrate through the gel blackberries quickly than longer ones.
Why does DNA migrate toward positive electrode?
Molecules migrate towards the opposite charge. A molecule with a negative charge, like DNA, will therefore be pulled towards the positive end.
What is the TBE composition?
TBE or Tris/Borate/EDTA, is a buffer solution containing a mixture of Tris base, boric acid and EDTA.
Why is important to add Mg ions? Are they co-enzymes or cofactors?
Mg ions are cofactors for restriction enzymes. Other ions are needed to transfer charge through the buffer solution.
Metal ion chelating in agarose gel system are important because they can foster the movement of DNA (as it is negatively charged due to why it migrate toward the positive electrode) by associating with it (as metal has positive charge). So they are cofactors.
How can DNA be detected in agarose gel?
The most convenient and commonly used method to visualize DNA in agarose gel is staining with the fluorescent dye ethidium bromide (a DNA dye).  Ethidium bromide is a DNA interchelator intercalator, inserting itself into the spaces between the base pairs of the double helix.
Why are DNA dyes dangerous for human health?
DNA dyes are dangerous for human health, as they have a cancerogenic effect, because they cause DNA modifications.
What should be done to prepare an agarose gel?
The gel is prepared by dissolving the agarose powder in an appropriate buffer, such as TAE or TBE, to be used in electrophoresis. The agarose is dispersed in the buffer before heating it to near-boiling point, but avoid boiling. The melted agarose is allowed to cool sufficiently before pouring the solution into a cast as the cast may warp or crack if the agarose solution is too hot. A comb is placed in the cast to create wells for loading sample, and the gel should be completely set before use.
What should not be done preparing an agarose gel?
1. Make sure that the agarose is fully dissolved in the buffer. If it is not dissolved well, again melt it some more time to dissolve completely.

2. Before casting the gel, the tray and comb should wipe with ethanol.

3. Make sure that the gel in the Chamber is immersed in the TAE Buffer.

4. Labelings should be  proper.

5. Ensure that the connections should be proper.

6. Before the  incubation step, ensure that the water bath is set at the correct temperature that we required or not.
Which piece of information can be find out from a DNA pattern bands?

If you get, through electrophoresis, the same DNA sample found at the crime scene, the person from whom that DNA fragment pattern was taken is probably the culprit of the murder.

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Was it possible to identify people in the past? How?

Yes, from 1901 it is possible to identify people from fingerprint recognition, from their ear print, from their teeth or bite impression, from their skin residues (sometimes under the jewelry, especially rings), from their retinal vessels and also from their blood typing (A, 0, AB, B), which were discovered by Karl Landsteiner in 1901. There are only four different types and lots of people can share the same type. This kind of marker could be used only to exclude somebody from a crime

When was used first DNA fingerprinting?

Fingerprints have been used since 1901, while DNA fingerprinting was used for the first time for a maternity test, liked to an immigrate dispute. This immagration case opened door for using DNA fingerprinting in forensic cases and for identity determination. Moreover, by that time, it began to be used to aid a criminal investigations.

Where can DNA be obtained from?

There are many potential source of DNA for forensic analysis and the most common are: BLOOD, that is an excellent source of human DNA in white blood cells; SEMEN, which contains sperm cells; SALIVA, which contains cellular material; the HAIR FOLLICLE at the base of human hairs contains cellular material rich in DNA; SKIN and DANDRUFF; SWEAT STAINS, which contain skin cells sloughed off; VAGINAL FLUIDS, NASAL SECRETIONS and URINE, which contain mucosal surfaces, which do contain DNA; FECES, which contain digestive system cells rich of DNA.

Who invented RFLP technique? When?

Restriction fragment length polymorphism (RFLP) is a technique invented in 1984 by the english scientist Alec Jeffreys during research into hereditary diseases. It is used for the analysis of unique patterns in DNA fragments in order to genetically differentiate between organism.
The RFLP technique exploits these differences in DNA sequences to recognize and study intraspecies variation.

What is a restriction enzyme?

A restriction enzyme is an enzyme that cuts DNA at or near specific recognition base sequences known as restriction side. These enzymes are found in bacteria.

What is restriction enzyme role in nature?

Restriction enzyme are used for biotechnology research, especially for DNA cloning and DNA fingerprinting. Different restriction enzymes recognise and cut different DNA sequences. Restriction enzyme are used to digest genomic DNA for gene analysis. This function allows to detemine how many copies of a gene are present in the genoma of  person, or how many mutations have occurred in a population.