Cell Biology Exam 1

B. cysteine

Disulfide bonds between ____ residues help stabilize protein conformation. A. methionine B. cysteine C. serine D. tyrosine

T

T or F: Adenines are added to the poly(A) tail of an mRNA molecule by RNA polymerase II transcribing a DNA template strand.

F

T or F: All functional DNA sequences inside a cell code for protein products.

T

T or F: By wobble pairing, a single tRNA is sometimes able to decode more than one codon sequence

F

T or F: DNA methylation by methyltransferases is a mechanism of epigenetic inheritance.

B. RNAi is induced when double-stranded, foreign RNA is present in the cell.

Which of the following statements about RNAi is true? A. The RNAi mechanism is found only in plants and animals. B. RNAi is induced when double-stranded, foreign RNA is present in the cell. C. RISC modifies complementary foreign RNA molecules with ubiquitin. D. siRNAs bind to miRNAs to induce RNAi.

A. Ubiquitination

Which posttranslational modification marks proteins to be located to the proteasome? A. Ubiquitination B. Glycosylation C. Methylation D. Phosphorylation

B. Proteases

Which type of enzyme hydrolyzes peptide bonds? A. Phosphatases B. Proteases C. Phosphodiesterases D. Kinases

B. Site E

After an amino acid has been linked to a peptide chain, the large ribosomal subunit shifts forward, moving the spent tRNA to which ribosome tRNA binding site before ejecting it? A. Site A B. Site E C. Site P D. Site T

A. 5'-CCA-3'

All mature tRNAs end with which sequence? A. 5'-CCA-3' B. 5'-ACC-3' C. 5'-GGA-3' D. 5'-CUA-3'

operons

Bacterial _____ contain a cluster of genes transcribed as a single RNA.

A. Proteolytic cleavage of the KDEL signal sequence from the protein

A protein contains a KDEL ER-retention signal sequence. Which protein processing mechanism would permit the protein to transport out of the endoplasmic reticulum? A. Proteolytic cleavage of the KDEL signal sequence from the protein B. Phosphorylation of the lysine residue of the KDEL signal sequence C. Ubiquitination of the lysine residue of the signal sequence D. Sequestration by a ER-resident chaperone protein.

C. introns; exons

During RNA splicing ____ are excised and _____ are ligated. A. snRNAs; scRNAs B. scRNAs; snRNAs C. introns; exons D. exons; introns

DNA ligases

During the mismatch repair (MMR), _____ reform the phosphodiester bonds between adjacent nucleotides.

protein phosphatases

Enzymatic _____ catalyze the removal of a phosphate group from a protein, often with high specificity for the phosphorylated site.

protein kinases

Enzymatic _____ catalyze the transfer of a phosphate group from ATP to a specific amino acid side chain on a target protein.

D. tRNA

Involved in translation termination, eRF-1 has a structure similar to which of the following choices? A. elF-1 B. IF-1 C. miRNA D. tRNA

A. Lysine 9 methylation

Methylation and acetylation are common changes made to histone H3, and the specific combination of these changes is sometimes referred to as the "histone code." Which of the following patterns will probably lead to gene silencing? A. Lysine 9 methylation B. Lysine 4 methylation and lysine 9 acetylation C. Lysine 14 acetylation D. Lysine 9 methylation and lysine 14 acetylation

T

T or F: Primase is needed to initiate DNA replication on both the leading and the lagging strand.

F

T or F: Purines always base-pair with purines, and pyrimidines always base-pair with pyrimidines.

T

T or F: Telomerase carries its own RNA molecule to use as a primer at the end of the lagging strand.

T

T or F: The DNA-binding motifs of transcription factors have an overall negative average.

T

T or F: The sequence of mRNA molecules can be changed after transcription has occurred.

F

T or F: There are 12 base-pairs in one complete turn of the B form of a DNA double helix.

D. nucleotide polymerization occurs only in the 5'-to-3' direction

Transcription is similar to DNA replication in that ___. A. an RNA transcript is synthesized discontinuously and the pieces are then joined together. B. it uses the same enzyme as that used to synthesize RNA primers during DNA replication C. the newly synthesized RNA remains paired to the template DNA D. nucleotide polymerization occurs only in the 5'-to-3' direction

D. RNA is single-stranded.

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because ____. A. RNA contains uracil and uses ribose as the sugar. B. RNA bases cannot form hydrogen bonds with each other. C. RNA nucleotides use a different chemical linkage between nucleotides compared to DNA. D. RNA is single-stranded.

D. Met-Leu-Ala-Arg-Tyr-Leu

Using the genetic code (Table on page 8), what amino acid sequence is produced from the mRNA sequence: 5'-AUGCUAGCUCGAUAUCUCUAG-3'? A. Met-Asp-Ala-Ile-Leu B. Met-Val-Arg-Ala-Phe C. Met-Leu-Gly-Tyr-Ala-Leu-Tyr D. Met-Leu-Ala-Arg-Tyr-Leu

C. elF-4E

Which factor makes direct contact with the 5' cap on mRNA? A. elF-4A B. elF-4B C. elF-4E D. elF-4G

D. homologous recombination

Which mechanism of the double-strand DNA break repair results in no loss of nucleotides at the site of repair? A. base excision repair B. nucleotide excision repair C. nonhomologous end joining D. homologous recombination

see picture

Which of the choices below represent the correct way to repair the mismatch shown?

C. 5'-AAGCGCTT-3'

Which of the following DNA strands can form a DNA duplex by pairing with itself at each position? A. 5'-AAGCCGAA-3' B. 5'-AAGCCGTT-3' C. 5'-AAGCGCTT-3' D. 5'-AAGCGCAA-3'

see picture

Which of the following accurately represents the directionality of DNA strands at one side of a replication fork?

A. The ribosome binds to the mRNA

Which of the following does NOT occur before a eukaryotic mRNA is exported from the nucleus? A. The ribosome binds to the mRNA B. The mRNA is polyadenylated at its 3' end C. 7-methylguanosine is added in a 5'-to-3' linkage to the mRNA D. RNA polymerase dissociates

D. U4-snRNP

Which of the following is NOT a component of the spliceosome? A. U1-snRNP B. U2-snRNP C. U3-snRNP D. U4-snRNP

B. RING finger

Which of the following is not an example of a transcription factor DNA-binding motif? A. helix-turn-helix B. RING finger C. Leucine zipper D. Zinc finger

A. 5'-TATA-3'

Which of the following sequences are usually located within eukaryotic promoters 25 base pairs away from the transcription start site and has a role in forming the transcription pre-initiation complex? A. 5'-TATA-3' B. 5'-CCA-3' C.5'- AUG-3' D. 5'-TAGG-3'

B. 5'-GGCGCACC-3'

Which of the following stable double-stranded DNA sequences listed below has the HIGHEST melting temperature? A. 5'-TATTGTCT-3' B. 5'-GGCGCACC-3' C. 5'- GACTCCTG-3' D. 5'-CTAACTGG-3'

D. The bottom strand is the template strand; RNA polymerase moves along this strand from the 3' to 5'

You have a segment of DNA that contains the following sequence: You know that the RNA transcribed from this segment contains the following sequence: Which of the following choices best describes how transcription occurs? A. The top strand is the template strand; RNA polymerase moves along this strand from the 5' to 3' B. The top strand is the template strand ; RNA polymerase moves along this strand from the 3' to 5' C. The bottom strand is the template strand; RNA polymerase moves along this strand from the 5' to 3' D. The bottom strand is the template strand; RNA polymerase moves along this strand from the 3' to 5'

tRNA

functions as carriers of amino acids.

miRNA

is an endogenous double-stranded RNA involved in RNA silencing.

gRNA

is involved in RNA editing.

snRNA

is involved in RNA splicing.

snoRNA

is involved with chemical modification of RNA.

C. Codon 3

Which of the below underlined codons will be selected as the translation initiator codon? A. Codon 1 B. Codon 2 C. Codon 3 D. Codon 4

A. 100 amino acid residues

An exported mRNA containing 300 nucleotides can initially be translated into a protein that is approximately how many amino acid residues in length? A. 100 amino acid residues B. 300 amino acid residues C. 600 amino acid residues D. 900 amino acid residues

DNA polymerases

At replication forks, ____ catalyze addition of nucleotides to the 3' end of a growing DNA strand by using a parental DNA strand as a template.

D. elF-4F

In eukaryotes, which of the following choices is NOT part of the translation pre-initiation complex? A. Ribosome small subunit B. elF-2 C. elF-3 D. elF-4F

B. Topoisomerases nick the phosphate backbone, allowing local unwinding of DNA ahead of replication fork.

The DNA duplex consists of two long covalent polymers wrapped around each other many times over their entire length. The separation of the DNA strands for replication causes the strands to be "overwound" in front of the replication fork. How does the cell relieve the torsional stress created along the DNA duplex during replication? A. Nothing needs to be done because the two strands will be separated after replication is complete. B. Topoisomerases nick the phosphate backbone, allowing local unwinding of DNA ahead of replication fork. C. Helicase unwinds the DNA and rewinds it after replication is complete. D. DNA repair enzymes remove torsional stress as they replace incorrectly paired bases.

A. 5'-PyPyPyPyPyPyNCAG-3'

The nucleotide consensus sequence found at the 3' splice site of intron-exon boundaries is ____. A. 5'-PyPyPyPyPyPyNCAG-3' B. 5'-GUAAGU-3' C. 5'-UACUAAC-3' D. 5'-AAUAAA-3'

A. H1

The octameric histone core is composed of four different histone proteins, assembled in a stepwise manner. once the core octamer has been formed, DNA wraps around it to form a nucleosome core particle. Which of the following histone proteins does NOT form part of the octameric core? A. H1 B. H2A C. H2B D. H4