Unit 6

Question 1

recombinant DNA

Answer 1

fragment of DNA composed of sequences originating from at least two different sources

Question 2

restriction endonucleases

Answer 2

enzymes that are able to cleave double-stranded DNA into fragments at specific sequences; also known as restriction enzymes

Question 3

recognition site

Answer 3

a specific sequence within double-stranded
DNA, usually palindromic and consisting of four to eight nucleotides, that a restriction endonuclease recognizes and cleaves

Question 4

sticky ends

Answer 4

fragment end of a
DNA molecule with short single-stranded overhangs, resulting from cleavage by a restriction enzyme

Question 5

blunt ends

Answer 5

fragment ends of a
DNA molecule that are fully base paired, resulting from cleavage by a restriction enzyme

Question 6

methylases

Answer 6

enzymes that add a methyl group to one of the nucleotides found in a restriction endonuclease recognition site, altering its chemical composition

Question 7

methyl group

Answer 7

CH3

Question 8

T4 DNA ligase

Answer 8

an enzyme used to join together DNA blunt or sticky ends

Question 9

gel electrophoresis

Answer 9

separation of charged molecules on the basis of size by sorting through a gel meshwork

Question 10

agarose

Answer 10

gel-forming polysaccharide found in some types of seaweed that is used to form a gel meshwork for electrophoresis

Question 11

polyacrylamide

Answer 11

artificial polymer used to form a gel meshwork for electrophoresis

Question 12

ethidium bromide

Answer 12

a carcinogenic, flat molecule that inserts itself among the rungs of the ladder of DNA and fluoresces under UV light

Question 13

fluoresces

Answer 13

glows under UV light because of the excitation of a molecule’s electrons

Question 14

plasmids

Answer 14

small circular pieces of DNA that can exit and enter bacterial cells

Question 15

copy number

Answer 15

number of copies of a particular plasmid found in a bacterial cell

Question 16

multiple-cloning site

Answer 16

region in plasmid that has been engineered to contain recognition sites of a number of restriction endonucleases

Question 17

cloned

Answer 17

a fragment of DNA that has been introduced into a foreign cell, resulting in exact copies of the original DNA fragment being made when the foreign cell replicates and divides

Question 18

transformation

Answer 18

introduction of foreign DNA, usually by a plasmid or virus, into a bacterial cell

Question 19

vectors

Answer 19

vehicles by which DNA may be introduced into host cells

Question 20

host cell

Answer 20

a cell that has taken up a foreign plasmid or virus and whose cellular machinery is being used to express the foreign DNA

Question 21

competent cell

Answer 21

a cell that readily takes up foreign DNA

Question 22

restriction endonuclease

Answer 22

Use: bacterial enzyme that cleaves
DNA sequences at a specific recognition site

Question 23

methylase

Answer 23

bacterial enzymes that add a methyl group to recognition sites to protect DNA from cleavage by restriction enzyme

Question 24

DNA ligase

Answer 24

enzyme that joins complementary fragments by reconstituting phosphodiester bond of DNA backbone

Question 25

gel electrophoresis

Answer 25

process by which DNA fragments of different lengths are separated by electrical current, negative charge of DNA, and constant charge-to-mass ratio

Question 26

plasmid

Answer 26

small circular DNA that has the ability to enter and replicate in bacterial cells and, therefore, can be used as a vector to introduce new genes into a bacterial cell

Question 27

polymerase chain reaction (PCR)

Answer 27

amplification of DNA sequence by repeated cycles of strand separation and replication

Question 28

DNA primers

Answer 28

short sequences of DNA nucleotides that are complementary to the opposing 3'-to-5' ends of the DNA target sequence that is to be replicated

Question 29

Taq polymerase

Answer 29

DNA polymerase, extracted from Thermus aquaticus, that is able to withstand high temperatures

Question 30

Thermus aquaticus

Answer 30

species of bacteria found in hot springs

Question 31

variable-length strands

Answer 31

mixture of strands of DNA that have been replicated and are of unequal length

Question 32

constant-length strands

Answer 32

mixture of strands of DNA that have been replicated and are of equal length

Question 33

polymorphism

Answer 33

any difference in DNA sequence, coding or non-coding, that can be detected between individuals

Question 34

restriction fragment length polymorphism (RFLP) analysis

Answer 34

a technique in which DNA regions are digested using restriction endonu-clease(s) and subiected to radioactive complementary DNA probes to compare the differences in DNA fragment lengths between individuals

Question 35

Southern blotting

Answer 35

a procedure that allows the DNA in an electrophoresis gel to be transferred to a nylon membrane while maintaining the position of the DNA band fragments

Question 36

hybridization

Answer 36

complementary base pairing between strands of nucleic acids via hydrogen bonding

Question 37

autoradiogram

Answer 37

gel pattern imprinted on X-ray film by radioactive probes

Question 38

Sanger dideoxy method

Answer 38

DNA sequencing technique based on DNA replication that uses dideoxy nucleoside triphosphates

Question 39

dideoxy analogue

Answer 39

nucleoside triphosphate whose ribose sugar does not possess a hydroxyl group on the 2' and the 3' carbon

Question 40

genetic screening

Answer 40

process by which an individual's DNA is scanned for genetic mutations

Question 41

gene therapy

Answer 41

the alteration of a genetic sequence in an organism to prevent or treat a genetic disorder

Question 42

pronociceptive transmitters

Answer 42

signal molecules that amplify pain sensation via a neurological pathway

Question 43

antinociceptive transmitters

Answer 43

signal molecules that dampen pain sensation via a neurological pathway

Question 44

antisense oligonucleotides

Answer 44

complementary DNA or RNA that anneals to mRNA and inhibits

Question 45

transgenic

Answer 45

organism in which foreign DNA has been artificially incorporated into its genome

Question 46

Ti plasmid

Answer 46

plasmid, found in Agrobacterium tumefaciens bacteria, that is able to enter plant cells

Question 47

Agrobacterium tumefaciens

Answer 47

type of bacteria that infects wounded plant cells and creates a crown gall

Question 48

Bt toxin

Answer 48

poisonous substance produced by Bacillus thuringiensis, which acts as a natural herbicide

Question 49

DNA fingerprinting

Answer 49

pattern of bands on a gel, originating from RFLP analysis or PCR, that is unique to each individual