Unit 4 Exam

Question 1

Which characteristic of DNA allows each strand of the molecule to act as a template that specifies the exact sequence of nucleotides in the other strand?

Answer 1

Complementarity of the bases

Question 2

You decide to repeat the Meselson-Stahl experiment, except this time you plan to grow the E. coli cells on light 14N medium for many generations and then transfer them to heavy 15N medium and allow them to grow. If the semiconservative model of DNA replication is correct, what is the expected distribution of DNA in the density gradient after one round of replication?

Answer 2

A single band of intermediate density.

Question 3

Genetic analysis of the DNA isolated from an unknown organism indicates that it contains the gene that codes for telomerase. Based on this information alone, you can conclude that this organism…

Answer 3

is eukaryotic

Question 4

Nucleotides have a phosphate group attached at the _________ blank carbon atom of the sugar.

Answer 4

5’

Question 5

Watson and Crick developed a model of DNA in which the two strands twist into the shape of a _________.

Answer 5

double helix

Question 6

DNA replication always proceeds by adding new bases to the _________ end of an existing strand.

Answer 6

3’

Question 7

After DNA replication is complete, each strand of the original molecule is bound to a new complementary strand. This process is known as…

Answer 7

semiconservative replication

Question 8

Which enzyme adds new nucleotides to the end of a growing strand?

Answer 8

polymerase

Question 9

DNA primase creates a short ______ primer that is complementary to a ______ template.

Answer 9

RNA; DNA

Question 10

As the two strands of DNA are unraveled, which enzyme relieves the strain on the two strands?

Answer 10

DNA gyrase

Question 11

The chemical bond connecting one nucleotide with the next along one strand of a DNA molecule is called a…

Answer 11

phosphodiester bond

Question 12

Chargaff’s rules for the pairing of nitrogen bases is…

Answer 12

A = T and G = C

Question 13

Information obtained by Franklin from X-ray crystallography on DNA suggested that it is shaped like a…

Answer 13

helix

Question 14

DNA consists of two antiparallel strands of nucleotides held together by…

Answer 14

hydrogen bonds

Question 15

The lagging strand is replicated with a series of Okazaki fragments and that is why its synthesis is considered to be…

Answer 15

discontinuous

Question 16

If 14% of the nucleotides from a DNA molecule contain the base T, what percent will contain the base G?

Answer 16

36%

Question 17

The site where the two original DNA strands separate and active replication occurs is called the…

Answer 17

replication fork

Question 18

Endonucleases and exonucleases are enzymes that can remove nucleotides from a polynucleotide chain. An endonuclease removes nucleotides _______ while an exonuclease removes nucleotides _________.

Answer 18

internally; from the ends of the chain

Question 19

In DNA, a purine must always pair with a pyrimidine and vice versa in order to ensure that…

Answer 19

the distance between the two phosphodiester backbones remains constant.

Question 20

During DNA replication, which enzyme removes the RNA primers and then fills in the gap?

Answer 20

DNA pol I

Question 21

In which cells would you expect to find the highest level of telomerase?

Answer 21

Cells that replenish the lining of the gut

Question 22

Telomeres protect _________ and are _________ sequences of DNA.

Answer 22

the ends of linear chromosomes from nucleases; specific short repeated

Question 23

The Central Dogma of biology can be stated as

Answer 23

DNA→ RNA→ Proteins

Question 24

Place the following in order, starting with the smallest (#1) and ending with the largest (#4).

Answer 24

nucleotide, codon, gene, chromosome

Question 25

DNA affects the traits of an organism by providing the instructions for synthesizing _________

Answer 25

proteins

Question 26

_________ is translated by the ribosomes and contains the code that specifies the sequence of amino acids in a polypeptide chain.

Answer 26

mRNA

Question 27

_________ combines with protein to form the 2 ribosomal subunits.

Answer 27

Ribosomal RNA

Question 28

_________ transports amino acids to the ribosomes for use in protein synthesis.

Answer 28

transfer RNA

Question 29

_________ plays a key role in the splicing reaction that removes introns from eukaryotic pre-mRNA.

Answer 29

small nuclear RNA

Question 30

_________ combines with protein to form particles that help ribosomes attach to the endoplasmic reticulum in eukaryotes.

Answer 30

SRP RNA

Question 31

_________ acts to cleave target mRNAs or inhibit the translation of target mRNAs present in the cytoplasm of eukaryotes.

Answer 31

micro RNA

Question 32

In eukaryotes, how can a single gene code for several different proteins?

Answer 32

A single pre-mRNA can be spliced to form different mature mRNAs by including different sets of exons

Question 33

Alteration of the nucleotide sequence in SRP RNA would most likely affect...

Answer 33

docking of ribosomes to the RER.

Question 34

A bacterial cell has a nonsense mutation in the gene that codes for hexokinase, an enzyme used during glycolysis. This mutation is most likely to affect the expression of this gene by...

Answer 34

causing early termination during the elongation cycle of translation.

Question 35

The complementary messenger RNA strand that would be synthesized from the DNA template sequence of 5' CTGAC 3' would be...

Answer 35

3' GACUG 5'

Question 36

Gene ________ refers to the combined processes of transcription and translation.

Answer 36

expression

Question 37

During transcription of mRNA in eukaryotes, some sequences are cut out of the primary transcript and the remaining sequences are joined together. This processing of mRNA is called _________

Answer 37

splicing

Question 38

During translation, amino acids are carried to the ribosome by

Answer 38

tRNA

Question 39

Ribosomes are complex aggregates of

Answer 39

RNA and proteins

Question 40

How many unique mRNA codons can be constructed from the four different RNA nucleotides?

Answer 40

64

Question 41

The tRNA nucleotide sequence that pairs with bases on the mRNA is called a(n)

Answer 41

anticodon

Question 42

During translation in prokaryotes, formation of the initiation complex requires all of the following except

Answer 42

RNA polymerase

Question 43

Eukaryotic mRNA molecules may contain noncoding sequences that must be removed before translation. These are called

Answer 43

introns

Question 44

Initiation of transcription differs from initiation of DNA replication in several ways. One difference is that initiation of transcription does not require

Answer 44

a primer

Question 45

Transcription in prokaryotes is carried out by _________, which unwind(s) and transcribe(s) the gene.

Answer 45

RNA polymerase

Question 46

In eukaryotes, each type of RNA polymerase recognizes a different...

Answer 46

promoter

Question 47

In eukaryotes, the 3' poly-A tail is attached to

Answer 47

mRNA

Question 48

During _______, a ribosome assembles a polypeptide whose amino acid sequence is specified by the nucleotide sequence in a molecule of mRNA.

Answer 48

translation

Question 49

Cells conserve energy and resources by making active proteins only when they are needed. If a protein is not needed, which of the following methods of control would be the most energy-efficient?

Answer 49

block transcription

Question 50

How does DNA polymerase differ from RNA polymerase?

Answer 50

Only DNA polymerase has a proofreading ability.

Question 51

The A, P, and E sites are progressively occupied by amino acids being assembled into a polypeptide. These sites are part of...

Answer 51

the large ribosomal subunit.

Question 52

You and a group of scientists are mapping out gene regulation in a new species. Based on what is currently known about control of gene expression, what type of regulation is likely to be most important for most genes in this species?

Answer 52

Initiation of transcription

Question 53

In order for transcription to be initiated

Answer 53

RNA polymerase must have access to the DNA double helix and must also be capable of binding to the gene's promoter.

Question 54

As a microbiologist you have been asked to investigate the regulation of a novel gene in a bacterial species. Given what is known about bacteria, the logical place to begin your investigation is

Answer 54

transcriptional regulation.

Question 54

A protein that regulates transcription by binding to the operator is known as the

Answer 54

repressor

Question 54

A cluster of functionally-related genes that are regulated together and encoded into a single mRNA molecule is called a(n)

Answer 54

operon