UAB Exam 4 by123

How do eukaryotic codons and prokaryotic codons compare?

A) Prokaryotic codons usually contain different bases than those of eukaryotes.

B) Prokaryotic codons usually specify different amino acids than those of eukaryotes.

C) The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no

intermediate molecules such as tRNAs in prokaryotes.

D) Codons are a nearly universal language among all organisms.

E) Eukaryotic codons require ribosomes for translation while prokaryotic codons do not

D

The TATA sequence is found approximately 25 nucleotides upstream from the start site of

transcription. This most probably relates to which of the following?

A) its involvement with binding the transcription factor that helps place polymerase II in the

correct location

B) its direct binding of polymerase II

C) the ability of this sequence to bind to the start site

D) the supercoiling of the DNA near the start site

E) the 3-D shape of a DNA molecule

A

If a protein is coded for by a single gene and this protein has six clearly defined domains,

which number of introns is the gene likely to have?

A) 1

B) 5

C) 6

D) 12

E) 7

B

Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because

A) metabolic enzymes require vitamin cofactors, and affected individuals have significant

nutritional deficiencies.

B) enzymes are made of DNA, and affected individuals lack DNA polymerase.

C) many metabolic enzymes use DNA as a cofactor, and affected individuals have mutations that

prevent their enzymes from interacting efficiently with DNA.

D) certain metabolic reactions are carried out by ribozymes, and affected individuals lack key

splicing factors.

E) genes dictate the production of specific enzymes, and affected individuals have genetic

defects that cause them to lack certain enzymes

E

Which of the following is directly related to a single amino acid?

A) the base sequence of the tRNA

B) the amino acetyl tRNA synthase

C) the three-base sequence of mRNA

D) the complementarity of DNA and RNA

E) a repeating 3 base sequence in telomeres

C

What happens during the process of transcription?

A) DNA is replicated.

B) RNA is synthesized.

C) Proteins are synthesized.

D) mRNA attaches to ribosomes.

E) tRNA attaches to ribosomes.

B

The molecule that links the genotype and phenotype of an organism, is (are)

A) protein.

B) mRNA.

C) tRNA.

D) receptor complexes.

E) ploidy.

A

Changes in a single nucleotide pair within a gene is called

A) substitution.

B) translocation.

C) point mutation.

D) silent mutation.

E) evolution

C

What molecular structure are codons part of?

A) a protein

B) mRNA

C) tRNA

D) rRNA

E) DNA

B

What does it mean when we say the genetic code is redundant?

A) A single codon can specify the addition of more than one amino acid.

B) The genetic code is different for different domains of organisms.

C) The genetic code is universal (the same for all organisms).

D) More than one codon can specify the addition of the same amino acid.

E) DNA is can be transcribed in different reading frames.

D

How does a plasma membrane protein become imbedded in the membrane?

A) Ribosomes attach to the plasma membrane and translation of the peptide occurs directly on

the PM.

B) Ribosomes enter the endoplasmic reticulum and make the proteins within the ER.

C) Once the signal peptide is translated, the ribosome complex is escorted to the PM, translation

continues and the peptide is inserted through a pore in the membrane.

D) Once the signal peptide is translated, the ribosome complex is escorted to the ER, translation

continues and the peptide is inserted through a pore in the membrane.

E) Once completed, the protein is escorted to the PM and a chaperone protein pushes it in

D

The term polyribosome refers to

A) a polymerase ribosome complex.

B) the beaded look of the rough ER.

C) the ribosome complex in eukaryotes.

D) the ribosome complex in prokaryotes.

E) a string of ribosomes attached to a mRNA

E

The white fur colouration of the "spirit bear" of British Columbia, is a result of

A) a point mutation, leading to a missense protein.

B) a point mutation leading to a nonsense protein.

C) albinism.

D) a deletion in the MC1 chromosome.

E) hybridization with polar bears.

E

If a nucleotide substitution switched a U for a C, such that the codon was read as CGC

instead of CGU, what would the effect be?

A) a misfolding of the protein

B) an incomplete protein

C) nothing, as the third nucleotide does not determine the amino acid used.

D) nothing, since both these codons code for arginine

E) it would initiate a tumour

D

If a nucleotide substitution switched an A for a U, such that the codon was read as UAA

instead of AAA, what would the effect be?

A) a silent mutation

B) a missense mutation

C) a nonsense mutation

D) no mutation as nucleotides in the first position are interchangeable

E) it would initiate a tumour

C

What would the anticodon be for a tRNA that transports phenylalanine to a ribosome?

A) UUU

B) AAA

C) TTT

D) CCC

E) GGG

B

If, after irradiating and growing cultures in enriched media, you see some red colonies, what

is the easiest way to confirm that the phenotype observed is due to a lack of adenine metabolism?

A) Grow them with and without adenine in the media.

B) Grow them with and without the adenine precursor.

C) You would have to see the DNA sequences.

D) Look for the protein products and compare them to wild type.

E) See if the colonies could survive with a higher dosage of UV irradiation.

A

What is the role of UV light in this circumstance?

A) It is a promoter.

B) It functions in RNA splicing.

C) It initiates RNA interference.

D) It is a mutagen.

E) It blocks tumour suppression.

D

What is the mechanism of information transfer from DNA to protein synthesis in eukaryotes?

A) DNA from a single gene is replicated and transferred to the cytoplasm, where it serves as a

template for protein synthesis.

B) Messenger RNA is transcribed from a single gene, and the mRNA transfers information from

the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.

C) Proteins transfer information from the nucleus to the ribosome, where protein synthesis takes

place.

D) Transfer RNA takes information from DNA directly to a ribosome, where protein synthesis

takes place.

E) DNA is replicated and transferred to the cytoplasm, translated to mRNA, which then serves as

a template for protein synthesis.

B

Which of the following occurs in prokaryotes but not in eukaryotes?

A) post-transcriptional splicing

B) concurrent transcription and translation

C) translation in the absence of a ribosome

D) gene regulation

E) use of redundant codons

B

What are the correct sizes of the following?

1. A primary transcript in the nucleus of a eukaryotic cell compared to the functional mRNA

2. A primary transcript in a prokaryotic cell compared to the functional mRNA

A) the same size; smaller than

B) larger than; the same size

C) larger than; smaller than

D) the same size; larger than

E) the same size; the same size

B

What does translation require?

A) mRNA, tRNA, DNA, and rRNA

B) mRNA, DNA, and rRNA

C) mRNA, tRNA, and rRNA

D) mRNA, tRNA, and DNA

E) tRNA and rRNA

C

During elongation, which site in the ribosome represents the location where a codon is being

read?

A) E site

B) P site

C) A site

D) the small ribosomal subunit

E) exit site

C

Once a peptide has been formed between the amino acid attached to the tRNA in the P site

and the amino acid associated with the tRNA in the A site, what occurs next?

A) translocation

B) reading of the next codon of mRNA

C) initiation

D) The codon-anticodon hydrogen bonds holding the tRNA in the A site are broken.

E) termination

A

Which one of the following, if missing, would usually prevent translation from starting?

A) exon

B) 5' cap

C) AUG codon

D) poly-A tail

E) ATP

C

Put the following events of elongation in prokaryotic translation in chronological order.

1. Binding of mRNA with small ribosomal subunit

2. Recognition of initiation codon

3. Complementary base pairing between initiator codon and anticodon of initiator tRNA

4. Base pairing of the mRNA codon following the initiator codon with its complementary tRNA

5. Attachment of the large subunit

A) 1, 2, 3, 4, 5

B) 2, 1, 4, 3, 5

C) 5, 4, 3, 2, 1

D) 1, 2, 3, 5, 4

E) 1, 5, 2, 3, 4

D

How does termination of translation take place?

A) The end of the mRNA molecule is reached.

B) A stop codon is reached.

C) The 3' cap is reached.

D) The poly-A tail is reached.

E) When the ribosome senses an intron

B

Post-translational modifications of proteins may include which of the following?

A) removal of introns

B) addition of a 5' cap

C) addition of a poly-A tail

D) addition of carbohydrates to form a glycoprotein

E) removal of exons

D

How might a single base substitution in the sequence of a gene affect the amino acid

sequence of a protein encoded by the gene, and why?

A) A single amino acid could change, but the reading frame is unaffected.

B) The amino acid sequence would be substantially altered, because the reading frame would

change.

C) All amino acids following the substitution would be affected, because the reading frame

would be shifted.

D) It is not possible for a single base substitution to affect protein structure, because each codon

is three bases long.

E) There would be no impact, as two or three base pairs must change to result in a change at the

amino acid level.

A

An original section of DNA has the base sequence 5'AGCGTTACCGT3'. A mutation in

this DNA strand results in the base sequence 5'AGGCGTTACCGT3'. This change represents

which of the following?

A) a missense mutation

B) a point mutation

C) a silent mutation

D) a frameshift mutation

E) a nonsensical mutation

D

When is a single base substitution in DNA least likely to be deleterious?

A) When a stop codon results

B) When the codon that results specifies the same amino acid as the original codon

C) When the amino acid substitution alters the tertiary structure of the protein

D) When the amino acid substitution at the active site of an enzyme

E) When a new start codon is inserted

B

Rank the following one-base point mutations (from most likely to least likely) with respect

to their likelihood of affecting the structure of the corresponding polypeptide.

1. insertion mutation within an intron

2. substitution mutation at the third position of an exonic codon

3. substitution mutation at the second position of an exonic codon

4. deletion mutation within the first exon of the gene

A) 1, 2, 3, 4

B) 4, 3, 2, 1

C) 2, 1, 4, 3

D) 3, 1, 4, 2

E) 4, 1, 3, 2

B

A mutation that inactivates the regulatory gene of a repressible operon in anE. colicell wouldresult in

A) continuous transcription of the structural gene controlled by that regulator.

B) complete inhibition of transcription of the structural gene controlled by that regulator.

C) irreversible binding of the repressor to the operator.

D) inactivation of RNA polymerase by alteration of its active site.

E) continuous translation of the mRNA because of alteration of its structure

A

Approximately what proportion of the DNA in the human genome codes for proteins orfunctional RNA?

A) 83%

B) 46%

C) 32%

D) 13%

E) 1.5%

E

What does the operon model attempt to explain?

A) the coordinated control of gene expression in bacteria

B) bacterial resistance to antibiotics

C) how genes move between homologous regions of DNA

D) the mechanism of viral attachment to a host cell

E) horizontal transmission of plant viruses

A

A mutation in this section of DNA could influence the binding of RNA polymerase to the

DNA:

A) operon

B) inducer

C) promoter

D) repressor

E) corepressor

C

How does active CAP induce expression of the genes of the lactose operon?

A) It terminates production of repressor molecules.

B) It degrades the substrate allolactose.

C) It stimulates splicing of the encoded genes.

D) It stimulates the binding of RNA polymerase to the promoter.

E) It binds steroid hormones and controls translation.

D

Muscle cells and nerve cells in one species of animal owe their differences in structure to

A) having different genes.

B) having different chromosomes.

C) using different genetic codes.

D) having different genes expressed.

E) having unique ribosomes.

D

In both eukaryotes and prokaryotes, gene expression is primarily regulated at the level of

A) transcription.

B) translation.

C) mRNA stability.

D) mRNA splicing.

E) protein stability.

A

In eukaryotes, transcription is generally associated with

A) euchromatin only.

B) heterochromatin only.

C) very tightly packed DNA only.

D) highly methylated DNA only.

E) both euchromatin and histone acetylation.

E

Eukaryotic cells can control gene expression by which of the following mechanisms?

A) histone acetylation of nucleosomes

B) DNA acetylation

C) RNA induced modification of chromatin structure

D) repression of operons

E) induction of operators in the promoter

A

This binds to a site in the DNA far from the promoter to stimulate transcription:

A) enhancer

B) promoter

C) activator

D) repressor

E) terminator

C

This can inhibit transcription by blocking the binding of positively acting transcription

factors to the DNA:

A) enhancer

B) promoter

C) activator

D) repressor

E) terminator

D

This is the site in the DNA located near the end of the final exon, encoding an RNA

sequence that determines the 3' end of the transcript:

A) enhancer

B) promoter

C) activator

D) repressor

E) terminator

E

The process of cellular differentiation is a direct result of

A) differential gene expression.

B) morphogenesis.

C) cell division.

D) apoptosis.

E) differences in cellular genomes.

A

A cell that remains entirely flexible in its developmental possibilities is said to be

A) differentiated.

B) determined.

C) totipotent.

D) genomically equivalent.

E) epigenetic.

C

Differentiation of cells is not easily reversible because it involves

A) changes in the nucleotide sequence of genes within the genome.

B) changes in chromatin structure that make certain regions of the genome more accessible.

C) chemical modifications of histones and DNA methylation.

D) frameshift mutations and inversions.

E) excision of some coding sequences.

D

Which of the following statements is true about stem cells?

A) Stem cells can continually reproduce and are not subject to mitotic control.

B) Stem cells can differentiate into specialized cells.

C) Stem cells are found only in bone marrow.

D) Stem cells are found only in the adult human brain.

E) Stem cell DNA lacks introns.

B

In most cases, differentiation is controlled at which level?

A) replication of the DNA

B) nucleosome formation

C) transcription

D) translation

E) post-translational activation of the proteins

C

Which of the following serve as sources of developmental information?

A) cytoplasmic determinants such as mRNAs and proteins produced before fertilization

B) signal molecules produced by the maturing zygote

C) ubiquitous enzymes such as DNA polymerase and DNA ligase

D) paternally deposited proteins

E) specific operons within the zygote genome

A

The MyoD protein

A) can promote muscle development in all cell types.

B) is a transcription factor that binds to and activates the transcription of muscle-related genes.

C) was used by researchers to convert differentiated muscle cells into liver cells.

D) magnifies the effects of other muscle proteins.

E) is a target for other proteins that bind to it.

B

The gene for which protein would most likely be expressed as a result of MyoD activity?

A) myosin

B) crystallin

C) albumin

D) hemoglobin

E) DNA polymerase

A

The general process that leads to the differentiation of cells is called

A) determination.

B) specialization.

C) identification.

D) differentialization.

E) cellularization.

A

Which of the following is established prior to fertilization in

Drosophila

eggs?

A) the anterior-posterior and dorsal-ventral axes

B) the position of the future segments

C) the position of the future wings, legs, and antennae

D) A and B only

E) A, B, and C

A

These genes are expressed by the mother, and their products are deposited into the

developing egg:

A) homeotic genes

B) segmentation genes

C) egg-polarity genes

D) morphogens

E) inducers

C

These genes form gradients and help establish the axes and other features of an embryo:

A) homeotic genes

B) segmentation genes

C) egg-polarity genes

D) morphogens

E) inducers

D

The product of the bicoid gene in

Drosophila could be considered a(n)

A) tissue-specific protein.

B) cytoplasmic determinant.

C) maternal effect.

D) inductive signal.

E) fertilization product.

B

The incidence of cancer increases dramatically in older humans because

A) the Ras protein is more likely to be hyperactive after age sixty.

B) proteasomes become more active with age.

C) as we age, normal cell division inhibitors cease to function.

D) the longer we live, the more mutations we accumulate.

E) tumor-suppressor genes are no longer able to repair damaged DNA.

D

Which of the following can contribute to the development of cancer?

A) random spontaneous mutations

B) mutations caused by X-rays

C) transposition

D) chromosome translocations

E) all of the above

E