Biology Exam 2

a nucleotide contains a penose sugar, a phosphate group, and a(n)

notrogen-containing base

Which of the following does the enzyme primase synthesize?

RNA primer

The ends of the linear chromosomes are maintained by

telomerase

The experiments by Hershey and Chase helped confirm that DNA was the hereditary material on the basis of the finding that:

They demonstrated that each strand serves as a template for synthesizing a new strand of DNA.

In DNA, bonding of A with T and bonding of C with G are examples of

complementary base pairing.

Complementary base pairing between nucleotides makes which process possible?

DNA replication prior to cell division

DNA carries genetic information in its

sequence of bases

If DNA of a particular species was analyzed and it was found that it contains 27 percent A, what would be the percentage of C?

23 percent

Which of the following statements about DNA and RNA is true?

In DNA, A pairs with T, whereas in RNA, A pairs with U.

The bases of nucleic acids are purines or pyrimidines. Which statement contrasting purines and pyrimidines is true?

Purines contain more atoms in fused rings, whereas pyrimidines contain fewer atoms in one ring.

Molecules consisting of only a pentose sugar and a nitrogenous base are called

nucleosides.

What is attached to the 5' carbon of deoxyribose in DNA?

phosphate

All of the following bases are found in DNA except

uracil

With a few exceptions, each human cell contains DNA in its nucleus. Which statement about any cell containing DNA is true?

Different genes may be expressed at different times in a single cell.

The double-stranded structure of DNA results from

hydrogen bonding within and between polynucleotide strands.

Ribose and deoxyribose are both found in nucleic acids. The difference between ribose and deoxyribose is that

ribose has a higher molecular weight than deoxyribose because of its extra hydroxyl group.

The diversity in DNA molecules is due to

base sequence differences

In the DNA double helix, the bases in one strand are complementary to the bases in the other strand. Therefore,

a purine in one strand will pair with only one type of pyrimidine in the other strand.

Which of the following components is not involved during the formation of the replication fork?

ligase

DNA utilizes the bases guanine, cytosine, thymine, and adenine. In RNA, _______ is replaced by _______.

thymine; uracil

Nucleic acids and proteins are both polymers made of a set of monomers. Complete the following analogy: _______ are to nucleotides as side chains are to amino acids.

nitrogenous bases

What type of bond connects two complementary nucleotides?

hydrogen

DNA differs from RNA in that

only DNA has an equal number of purines and pyrimidines.

Unlike pyrimidines, purines have a _______ structure.

double ring

At what level of the central dogma are genes regulated?

all

A gene which is usually turned down but can be activated is under negative control.

true

How might antisense RNA affect translation?

It can interfere with ribosome binding by blocking binding sites.

nucleosomes inhibit

assembly of transcription factors

Proteins that block the passage of RNA polymerase are called:

repressors

How do DNA binding proteins find their target sequences?

through the shape of the sequence

All of the genes involved in functioning of the lac operon are inducible.

true

a translational regulatory protein:

binds to mRNA and prevents translation

What effect would you expect if gene expression of the lac operon were completely repressed?

all of these

which is an example of heterochromatin?

tightly packed chromatin with little gene expression

which is an example of euchromatin?

lossely packed chromatin with lots of gene expression

the role of methylation of DNA is now viewed as

insuring that genes that are turned off, stay off

Post-translational regulation changes protein function by

adding or subtracting small chemical molecules

genes within an operon:

all of the above

chromatin organization regulates gene expression by

blocking transcription factors from promoters

how does lactose interfere with the lacrepressor

it binds to the repressor altering its shape

which of the following would you expect to find in an inducible system?

A repressor protein, which is bound to DNA in absence of an inducing factor

transcriptional regulation:

all of these

the most common form of gene expression regulation in both bacteria and eukaryotes is

transcriptional control

translation repressor proteins may shut down translation of processed mRNA transcripts by

resetting the reading frame

Gene expression includes which of the following?

transcription and translation

Suppose the 5ʹ-to-3ʹ coding strand of DNA is GTCTATGCATTA.
What is the template DNA strand that would be used for transcription?

3ʹ-CAGATACGTAAT-5ʹ

If a strand of mRNA has the sequence 5ʹ-CUGUCA...ACUC-3ʹ (with […] representing the intervening sequence), what was the template strand of DNA used to produce this mRNA?

3ʹ-GACAGT...TGAG-5ʹ

Suppose that nucleic acid hybridization experiments revealed that the mRNA–DNA complexes form different loop patterns depending on which cell type is the source of the mRNA. Such data would support the

existence of alternative splicing.

in the process of transcription

an RNA molecule is synthesized from a DNA template.

When eukaryotic DNA is hybridized with mRNA, the hybrid molecules contain loops of DNA, which are

introns

the synthesis of DNA from RNA is called

reverse transcription

Which of the following is another name for the template strand (the strand of DNA that is transcribed)?

antisense strand

exons are

spliced together from the original transcript.

The difference between mRNA and tRNA is that

tRNA has a more elaborate three-dimensional structure.

Humans share the same genetic code with

all living organisms, with a few exceptions

The regions of DNA in a eukaryotic gene that contain noncoding base sequences are called

introns

Which statement about pre-mRNA splicing is false?

it is common in prokaryotes

The poly A tail added to pre-mRNA

increases mRNA stability

The promoter region of a gene has undergone an inversion with the 3′ end break point within the initiation site. This will affect the transcription of this gene in all of the following ways except the

separation of the double stranded DNA

Greater numbers of base changes are found in mRNA than in replicated DNA from the same gene sequence, because RNA polymerase

does not proofread

Which is not true about a promoter sequence?

it consists of the specific nucleotides AUG

Which of the following correctly describes uracil and where is it found?

It is a nitrogenous base found in RNA only

Which statement about RNA is false?

Messenger RNAs are produced on ribosomes.

Which of the following is one important distinction between prokaryotic and eukaryotic mRNA?

Eukaryotic mRNA is generally monocistronic.

Which molecule is used in transcription?

GTP

An mRNA has the sequence 5′-AUGAAAUCCUAG-3′. What is the template DNA strand for this sequence?

5′-CTAGGATTTCAT-3′

The guanosine triphosphate (GTP) cap that is added to the 5ʹ end of primary mRNA

facilitates the binding of mRNA to ribosomes.

Which statement about RNA is false?

messenger RNAs are produced on ribosomes

Aside from using T instead of U, the coding strand of DNA is _______ to the mRNA.

identical in sequence

Before the details of transcription and translation were worked out, Crick hypothesized a unidirectional flow of information from _______ to _______. He called this model the central dogma of molecular biology.

DNA; protein

The transfer of information from DNA to RNA occurs during _______, while the transfer of information from RNA to protein occurs during _______.

transcription; translation

Suppose that the coding region of a gene contains 1,800 base pairs, with 570 in exon 1, with 420 in exon 2, and with 810 in exon 3 (not counting the stop codon). The protein translated from this gene will consist of _______ amino acids.

597

In a cancer cell, a tumor suppressor gene is not being transcribed. Analysis of the gene’s protein-coding regions on both chromosomes does not reveal any mutations. Another explanation could be that one or more mutations in the gene’s _______ region could be disrupting transcriptional activation.

promoter

Which mutation is least likely to be a frame-shift mutation?

an insertion of six nucleotides

The anticodon 3ʹ-UAC-5ʹ will bind to which of the following codons?

5ʹ-AUG-3ʹ

A charged tRNA has _______ attached.

an amino acid

Which is not true about a promoter sequence?

it consists of the specific nucleotides AUG

The formation of a peptide bond between an amino acid at the P site and an amino acid at the A site during translation is catalyzed by

the large ribosomal subunit

the stop codons code for

no amino acid

A signaling protein involved in the activation of the cell cycle is found to be overactive in a cancer cell. Analysis of the protein indicates that its size is smaller than normal. The protein’s mRNA sequence is found to lack sequence that encodes the regulatory domain of the protein. Sequencing of the genomic DNA reveals that the lost sequence corresponds to one of two exons that encode the regulatory domain and that there is a mutation in a(n) _______ at the boundary of the missing exon and its preceding intron.

RNA splicing site

If a mutation occurs such that splicing does not remove one of the introns in a gene, what effect will this have on the protein encoded by that gene?

Translation will continue, but it is likely that a nonfunctional or aberrant protein will be made.

Which statement about translation is false?

An mRNA molecule can be translated by only one ribosome at a time.

Which statement about mutations is true?

all transitions are point mutations

During translation elongation, the growing polypeptide chain moves to

the tRNA occupying the P site

Based on the complexity of tRNA’s function, one might conclude that the number of different tRNA molecules that exist is surprisingly small. This discrepancy is possible because the

third position of the codon can pair with unusual bases in the anticodon.

In eukaryotic cells, translation occurs in the _______ and transcription occurs _______.

cytoplasm; in the nucleus

The portion of the tRNA molecule that works with the mRNA to accomplish complementary base pairing is called the

anticodon

Which statement about the flow of genetic information is true?

DNA encodes information that is transcribed into RNA, and RNA encodes information that is translated into proteins.

One can argue that although the existence of retroviruses represents a complication of Crick’s central dogma, it does not contradict it. The replication mechanism of retroviruses does not contradict the essence of the central dogma, because

even in retroviruses, information in proteins is not converted into DNA information.

Which type of mutation involves two different nonhomologous chromosomes?

translocations

The wobble phenomenon occurs at _______end of the anticodon and helps explain why the _______ end of the codon shows the most redundancy

the 5ʹ; 3ʹ

Humans share the same genetic code with

all living organisms, with a few exceptions

A charged tRNA travels across a ribosome from the _______ site, to the _______ site, and then to the _______ site.

A; P; E

Because of the redundancy in the genetic code, many mutations in the coding regions of genes are

silent mutations

If the following synthetic RNA were added to a test tube containing all the components necessary for protein translation to occur, what would the amino acid sequence be?
5ʹ-AUAUAUAUAUAU-3ʹ

Isoleucine → tyrosine → isoleucine → tyrosine

Ribosomes are a collection of _______ that are needed for _______.

proteins and rRNAs; translation

The adaptor between mRNA and a protein is

tRNA

If there were only three kinds of nucleotides, how many different types of codons would a genetic code have? (Assume that the codons are three nucleotides long.)

27

A researcher compares the dog and human sequences of gene X and its protein product. The nucleotide sequences of the two different species’ genes are 87% identical, whereas the amino acid sequences of the proteins are 99% identical. The discrepancy between the nucleotide and amino acid levels of sequence identity is possible because the genetic code is

redundant

If the coding region of an mRNA is 2,400 nucleotides long, how many codons does it have?

800