Chapter 7

Question 1

forward mutation

Answer 1

a mutation that changes a wild-type allele of a gene to a different allele

Question 2

reverse mutation/ reversion

Answer 2

cause a novel allele to revert back to wild type

Question 3

substitution

Answer 3

occurs when a base at a certain position in one strand of the DNA molecule is replaced by one of the three other bases

Question 4

transitions

Answer 4

one purine replaces the other purine; pyrimidine replaces the other

Question 5

transversions

Answer 5

purine changes to pyrimidine and vice cersa

Question 6

deletion

Answer 6

occurs when a block of one or more nucleotide pairs is lost from a DNA molecule

Question 7

insertion

Answer 7

the addition of one or more nucleotide pairs

Question 8

point mutations

Answer 8

affect one or just a few base pairs in the DNA and this alter only one gene at a time

Question 9

What did Salvador Luria and Max Delbruck devise an experiment for?

Answer 9

Designed a fluctuation test to show that bacterial resistance arises from mutations that exist before exposure to bacteriophages.

Question 10

replica plating

Answer 10

demonstrate more directly that mutations conferring bacterial resistance occur before the cells encounter the bactericide that selects for their resistance

Question 11

How are mutations created?

Answer 11

By two different events:

• Damaged by chemical reactions of radiation
• Mistakes can occur when DNA is copied during replication

Question 12

depurination

Answer 12

DNA alteration in which the hydrolysis of a purine base, either A or G, from the deoxyribose-phosphate backbone occurs.

Question 13

thymine-thymine dimers

Answer 13

causes adjacent thymine residues to become chemically linked

Question 14

mutagen

Answer 14

any physical or chemical agent that raises the frequency of mutations above the spontaneous rate

Question 15

base analogs

Answer 15

similar in chemical structure to the normal nitrogenous bases that the replication machinery can incorporate them into DNA

Question 16

intercalators

Answer 16

: flat, planar molecules that can sandwich themselves between successive base pairs and disrupt the machinery for replication, generating deletions, or insertions of a single base pair

Question 17

base excision repair

Answer 17

particularly important in the removal of uracil from DNA

Question 18

homologous recombination

Answer 18

can be used to repair most double-strand breaks accurately through complementary base pairing.

Question 19

non-homologous end-joining (NHEJ)

Answer 19

bind the DNA ends at the site of the breakage and protect the ends from nucleases.

Question 20

methyl-directed mismatch repair

Answer 20

backup repair system that easily recognize the incorrectly matched base pair because the improper base pairing distorts the double helix, resulting in abnormal bulges and hollows.

Question 21

auxotroph

Answer 21

a nutritional mutant microorganism that requires supplementation with substances not needed by wild-type strains

Question 22

prototroph

Answer 22

an organism that does NOT require the addition of a substance

Question 23

proteins

Answer 23

polymers composed of amino acids

Question 24

dipeptide

Answer 24

A pair of amino acids connected together

Question 25

oligopeptide

Answer 25

several amino acids linked together

Question 26

polypeptide

Answer 26

amino acid chains that make up proteins that contain hundreds to thousands of amino acids joined by peptide bonds

Question 27

N terminus

Answer 27

Start of a protein or polypeptide where one end that contains a free amino group that is NOT connected to any other amino acid

Question 28

C terminus

Answer 28

contains a free carboxylic acid group

Question 29

missense mutations

Answer 29

a genetic alteration that causes the substitution of one amino acid for another

Question 30

primary structure

Answer 30

linear sequence of amino acids within a polypeptide

Question 31

secondary structure

Answer 31

localized regions with a characteristic geometry

Question 32

tertiary structure

Answer 32

three-dimensional structure of the entire population

Question 33

denatured

Answer 33

when proteins unfold when exposed to urea and mercaptoethanol or to increasing heat of pH

Question 34

quarternary structure

Answer 34

The three-dimensional configuration of subunits in a multime