Bio Exam 2 Multiple Choice

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

Nucleosides

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 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

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

Thymine; uracil

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

Phosphate

All of the following bases are found in DNA except

Uracil

DNA differs from RNA in that

Only DNA has an equal number of purines and pyrimidines

Complementary base pairing between nucleotides makes which process possible?

DNA replication prior to cell division

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

Ligase

A nucleotide contains a pentose sugar, a phosphate group, and a(n)

Nitrogen‑containing base

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

Complementary base pairing

Which of the following does the enzyme primase synthesize?

RNA primer

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

Nitrogenous 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

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

DNA carries genetic information in its

Sequence of bases

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

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

What type of bond connects two complementary nucleotides?

Hydrogen

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 repeating structure of a polynucleotide is made of

Alternating sugar and phosphate groups

The diversity in DNA molecules is due to

Base sequence differences

Unlike pyrimidines, purines have a _______ structure.

Double‑ring

Post‑translational regulation changes protein function by

Adding or subtracting small chemical molecules

Which is an example of euchromatin?

Loosely packed chromatin with lots of gene expression

How might antisense RNA affect translation?

It can interfere with ribosome binding by blocking binding sites

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

All of these

At what level of the central dogma are genes regulated?

All

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

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

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

True

Nucleosomes inhibit

Assembly of transcription factors

Proteins that block the passage of RNA polymerase are called:

Repressors

The role of methylation of DNA is now viewed as

Insuring that genes that are turned off, stay off

Chromatin organization regulates gene expression by

Blocking transcription factors from promoters

Transcriptional regulation:

All of these

Genes within an operon:

All of the above

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

Resetting the reading frame

A translational regulatory protein:

Binds to mRNA and prevents translation

How does lactose interfere with the lac‑repressor

It binds to the repressor altering its shape

Which is an example of heterochromatin?

Tightly packed chromatin with little gene expression

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

Transcriptional control

Exons are

Spliced together from the original transcript

Which statement about pre‑mRNA splicing is false?

It is common in prokaryotes

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

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

5′‑CTAGGATTTCAT‑3′

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

Does not proofread

Gene expression includes which of the following?

Transcription and translation

The synthesis of DNA from RNA is called

Reverse transcription

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

Introns

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

Antisense strand

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

Facilitates the binding of mRNA to ribosomes

In the process of transcription,

An RNA molecule is synthesized from a DNA template

If a strand of mRNA has the sequence 5′‑CUGUCA...ACUC‑3′, what was the template strand of DNA used to produce this mRNA?

3′‑GACAGT...TGAG‑5′

Which statement about RNA is false?

Messenger RNAs are produced on ribosomes

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

The difference between mRNA and tRNA is that

tRNA has a more elaborate three‑dimensional structure

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

Eukaryotic mRNA is generally monocistronic

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

3′‑CAGATACGTAAT‑5′

Which molecule is used in transcription?

GTP

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

It is a nitrogenous base found in RNA only

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

Identical in sequence

The poly A tail added to pre‑mRNA

Increases mRNA stability

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

Introns

The gene product transfer RNA (or tRNA) translates

mRNA into polypeptide

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

the 5′; 3′

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

A; P; E

The stop codons code for

no amino acid

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

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

The anticodon 3′‑UAC‑5′ will bind to which of the following codons?

5′‑AUG‑3′

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

anticodon

In a cancer cell, a tumor suppressor gene is not being transcribed. Another explanation could be mutations in the gene's _______ region disrupting transcriptional activation.

promoter

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

597

The tRNA moves between three sites along the ribosome: A, E, and P. In chronological order, what is the pattern of residence of a given tRNA molecule at those sites?

A, then P, then E

A signaling protein in a cancer cell is smaller than normal due to loss of an exon. The mutation is in a(n)

RNA splicing site

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

Which is not true about a promoter sequence?

It consists of the specific nucleotides AUG

The adaptor between mRNA and a protein is

tRNA

The number of different tRNA molecules is small because

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

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

proteins and rRNAs; translation

An example of an ambiguous genetic code is one

in which CCU could code for either alanine or leucine

A researcher finds dog and human gene X are 87% identical at DNA level but 99% identical at protein level. This is because the genetic code is

redundant

If the synthetic RNA 5′‑AUAUAUAUAUAU‑3′ is translated, the amino acid sequence is

Isoleucine → tyrosine → isoleucine → tyrosine

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

transcription; translation

If codons are four bases long, the organism could have _______ different amino acids.

256

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

cytoplasm; in the nucleus

Which statement about codons and anticodons is true?

At contact, the codon and the anticodon are antiparallel to each other

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

silent mutations

Which type of mutation involves two different nonhomologous chromosomes?

Translocations

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

An insertion of six nucleotides

Humans share the same genetic code with

all living organisms, with a few exceptions

During translation elongation, the growing polypeptide chain moves to

the tRNA occupying the P site

If there were only three kinds of nucleotides, how many different types of codons would a genetic code have?

27

Which statement about translation is false?

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

Retroviruses don't contradict the central dogma because

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

A charged tRNA has _______ attached.

an amino acid

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

800