homework#8 (tut 17-18)

Question 1

Short segments of newly synthesized DNA are joined into a continuous strand by

Answer 1

ligase

Question 2

After DNA replication is completed,

Answer 2

each new DNA double helix consists of one old DNA strand and one new DNA strand

Question 3

The action of helicase creates

Answer 3

replication forks and replication bubbles

- A replication fork is the transition region between paired and unpaired DNA strands.

Question 4

Why is the new DNA strand complementary to the 3’ to 5’ strands assembled in short segments?

Answer 4

DNA polymerase can assemble DNA only in the 5’ to 3’ direction

Question 5

An old DNA strand is used as a _____ for the assembly of a new DNA strand.

Answer 5

template

Question 6

What is meant by the description “antiparallel” regarding the strands that make up DNA?

Answer 6

The 5’ to 3’ direction of one strand runs counter to the 5’ to 3’ direction of the other strand.

Question 7

Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?

Answer 7

DNA in both daughter cells would be radioactive.

Question 8

An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?

Answer 8

5’ A C G U U A G G 3’

Question 9

The leading and the lagging strands differ in that

Answer 9

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

Question 10

A new DNA strand elongates only in the 5’ to 3’ direction because

Answer 10

DNA polymerase can only add nucleotides to the free 3’ end.

Question 11

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

Answer 11

It joins Okazaki fragments together.

Question 12

A particular triplet of bases in the template strand of DNA is 5’ AGT 3’. The corresponding codon for the mRNA transcribed is

Answer 12

3’ UCA 5’.

Question 13

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following?

Answer 13

A gene from an organism can theoretically be expressed by any other organism.

Question 14

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is

Answer 14

UUU.

Question 15

What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?

Answer 15

transcription

Question 16

What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?

Answer 16

translation

Question 17

Which of these correctly illustrates the pairing of DNA and RNA nucleotides?

Answer 17

GTTACG

CAAUGC

Question 18

The direction of synthesis of an RNA transcript is

Answer 18

5’ —> 3’

Question 19

What enzyme catalyzes the attachment of an amino acid to tRNA?

Answer 19

aminoacyl-tRNA synthetase

Question 20

The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence

Answer 20

CUG

Question 21

The initiator tRNA attaches at the ribosome’s _____ site.

Answer 21

P

Question 22

True or false? A codon is a group of three bases that can specify more than one amino acid.

Answer 22

false

A codon is a group of three bases that can specify only one amino acid.

Question 23

Which of the following statements about mutations is false?

Answer 23

A knock-out mutation results in a total absence of the mutated protein.

Question 24

If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?

Answer 24

Deletion.

Question 25

Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?

Answer 25

One addition and one deletion mutation.

Question 26

If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein?

Answer 26

2

Question 27

If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred?

Answer 27

An addition mutation and a deletion mutation.