II. Reconstruct the following text using the words from the box to fill in the blanks. What do you think about extraterrestrial life?

cycles strands primers copies diseases nucleotides deoxyribonucleic acid test complementary

enzyme blood piece fragment segment technique round tube

duplicated amplify replicated multiplied research identify heating sufficient

Polymerase Chain Reaction (PCR) is a (1)_________ in molecular biology by which a small fragment of (2)_________ can be rapidly cloned, or (3)_________, to produce multiple DNA (4)_________. PCR can be used to (5)_________ individuals from minute amounts of tissue or (6)_________, to diagnose genetic (7)_________, and to (8)_________ evolution.

PCR proceeds in a series of (9)_________, or rounds. Each successive (10)_________ doubles the amount of DNA and thus more than 1 billion copies of a single DNA (11)_________ can be made in just a few hours. Performed in a test (12)_________, PCR mirrors the way in which DNA is (13)_________ within a cell. To perform PCR, scientists isolate the piece of DNA to be amplified ((14)_________) in a test tube and heat it to separate the two (15)_________ of the molecule. As cooling occurs, short pieces of DNA called (16)_________ are added to the test tube. The primers attach to each strand, marking the (17)_________ that will be cloned. Free-floating nucleotides and an (18)_________ called DNA polymerase are then added to the mixture. DNA polymerase uses the free-floating (19)_________ to build a (20)_________ copy of each amplified DNA segment, resulting in two new double-stranded DNA molecules. Each cycle of (21)_________ and cooling doubles the amount of the desired DNA fragment in the (22)_________ tube. In a matter of hours, scientists can obtain millions of copies of a desired (23)_________ of DNA. PCR enables scientists to (24)_________ traces of DNA found at a crime scene or in a fossil animal to produce (25)_________ quantities to study.

III. Reconstruct the text below putting the extracted fragments (a-j) into their correct places (1-10). Make a written translation of the passage into Ukrainian

PCR and recombinant DNA techniques create large amounts of DNA segments. To study the structure of these segments, (1)____. This technique can be used to identify genes in humans, (2)____ such as fruit flies. It can also be used to compare the DNA found from blood or hair samples at a crime scene (3)____. In gel electrophoresis, restriction enzymes break up the DNA under study (4)____. Solutions containing these fragments are placed within a thick gel. An electric current is applied to the gel, (5)____. All of the restriction fragments begin to move from the negative end of the gel toward the positive end. The smaller fragments move faster than the larger fragments. When the current shuts off, typically after several hours, (6)____, with the smaller ones closer to the positive end. The dispersed fragments display a pattern resembling a bar code. Each bar in this pattern contains DNA fragments of a certain size. Scientists can identify specific restriction fragments (7)____. A complementary sequence of DNA can be used as a probe to (8)____. Scientists may use DNA found in blood at a crime scene as the probe to see (9)____. If pairing occurs, the DNA from the crime scene is from the same person (10)____.

1. by their location on the gel;

2. causing one end of the gel to have a positive charge and the other to have a negative charge;

3. find a restriction fragment on the gel that has a particular nucleotide sequence;

4. if it pairs up with any of the DNA fragments in the gel electrophoresis;

5. into restriction fragments of varying lengths;

6. researchers use a process known as gel electrophoresis;

7. that have previously been identified in other organisms;

8. the DNA fragments have spread out across the gel;

9. who provided the DNA sample for the gel electrophoresis;

10. with the DNA of a suspect in the crime.