Bio Practice Exam

In a specific DNA sequencing method, di-deoxy-nucleoside- triphosphates (ddNTP's) are involved to produce replicated DNA strands of varying lengths. Once a ddNTP is incorporated into the growing strand of DNA, replication is stopped. Why does the incorporation of a ddNTP in a newly synthesized strand of DNA cease replication?

A ddNTP has no 3' hydroxyl group available to form a phosphodiester bond with the phosphate of the next incoming dNTP.

Which best describes the characteristics and function of a 5'-methyl-guanosine cap of a eukaryotic mRNA?

A methylated purine that is added, to the first nucleotide of the transcript to protect the mRNA from degradation by nucleases in the cytoplasm.

A gene in a lab is cloned and found to code for a histone methyl's enzyme. This enzyme regulates gene expression by?

Condensing the chromatin tighter at the target gene, thereby inhibiting transcription.

SINES (short interspersed nuclear elements)? a. are approximately 300 base pairs long b. are LTR (long terminal repeats) containing retrotransposons c. are present in over 1 million copies in the human genome d. a and c

D. A and C ; are approximately 300 base pairs long, are present in over 1 million copies in the human genome.

When DNA synthesis is initiated at the origin of replication, the two parental strands are replicated? a. in opposite directions b. same direction c. one continuously and one discontinuously d. A and C are correct

D. A and C are correct; in opposite directions and one continuously and one discontinuously.

The ability of DNA to denature is important for which process? a. DNA synthesis b. nucleic acid hybridization experiments c. RNA synthesis d. all of these

D. all of these

What do leucine zippers do during transcription regulation?

Form hydrogen bonds in the major groove of helices

Which of the following is a fundamental difference between gene regulation in bacteria compared to eukaryotes? a) In bacteria, but not eukaryotes, there is a specific sequence that specifies where RNA polymerase binds and initiates transcription. b) In eukaryotes, but not bacteria, transcription can be influenced by how effectively the DNA sequence of a promoter region interacts with histone octomers. c) Transcription regulation is the most widespread form of control of gene expression in bacteria but not in eukaryotes. d) Gene regulation is readily reversible in eukaryotes but not bacteria.

In eukaryotes, but not bacteria, transcription can be influenced by how effectively the DNA sequence of a promoter region interacts with histone octomers.

DNA that is transcriptionally active?

Is more susceptible to DNase I digestion.

When the ribosome reaches the end of the coding region of an mRNA?

It releases the free polypeptide.

For transcription in eukaryotes, either strand of double-stranded DNA may be the template strand. What determines which strand is the template strand?

The base sequence of the promoter (TATA box)

Which of the following descriptions best describes the process of splicing of a eukaryotic primary RNA transcript?

The exons are linked together, and the introns are removed. This process is driven via two consecutive transesterification reactions between the 2'-hydroxyl of one nucleotide and the 5'-phosphate of another.

If she moves (reference above) the repressor gene (lac I), along with its promoter, to a position at some several thousand base pairs upstream from its normal position, which will you expect to occur?

The lac operon will function normally

What is the function of the poly- A tail that is added to a eukaryotic mRNA after transcription?

To protect the transcript from degradation by nucleases.

which of the following is a protein that is involved in translation? a. topoisomerase b. ribosomal RNA c. RNA polymerase d. aminoacyl-tRNA synthetase

aminoacyl-tRNA synthetase

In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision repair mechanism. These individuals are unable to repair DNA damage caused by ultraviolet light. Multiple basal cell carcinomas and other skin malignancies frequently occur at a young age in those with XP. Which of the following are the most prominent types of mutations in individuals suffering from XP? a. telomere shortening b. thymine dimers c. mismatch repair d. methylation of purines e. all of these

b. thymine dimers

What would the most likely result of a prokaryotic species that develops a mutation that allows it to encode for the enzyme telomerase? a. The prokaryotic species would likely have a longer life-span due to the fact that its telomeres do not ever shorten. b. The prokaryotic species would have the capability to divide more rapidly because telomerase speeds the last step of DNA replication. c. There would be no effect on a prokaryote if it developed this mutation.

c. There would be no effect on a prokaryote if it developed this mutation.

The error rate in the human genome is 3.4 bases per round of replication. All the following contribute to error except? a. DNA polymerase b. homologous recombination c. polyadenylation d. base excision pair

c. polyadenylation

suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. She decides to use this technique to study the lac operon. If she leaves the promoter in place but moves the operator downstream to the far end of the operon past the three structural genes, which of the following would likely occur when the cell is exposed to lactose? a) The operon will never be transcribed b) The repressor protein will no longer be produced c) The structural genes will be transcribed continuously

c. the structural genes will be transcribed continuously.

what is the function of topoisomerase I? a. to relieve torsional stress in nuclear DNA during replication. b. to splice together exons during transcription. c. to remove DNA supercoils during transcription. d. both a and c

d. Both a and c to relieve torsional stress in nuclear DNA during replication and to remove DNA supercoils during transcription.

Cells preserve their identity after cell division with which of the following? a. DNA methylation b. remembered positive feedback loops c. maintenance of chromatin structure d. all of the above

d. all of the above

Chloramphenicol blocks the peptidyl transferase reaction on ribosomes. Which of the following processes are inhibited? a. splicing b. 5' end capping c. base excision repair d. protein elongation

d. protein elongation

Under which conditions will the lac Z gene be expressed at the highest rate?

no glucose, high lactose

In eukaryotes, tandemly repeated genes encode?

rRNAs

Which of the following is not a structural motif found in a DNA- binding domain? a) homeodomain b) zinc-finger c)helix-loop-helix d) random-coil acidic domain

random- coil acidic domain

DNA polymerase proofreading results in?

removal of a mismatched base and its replacement by the correct base

Why did DNA evolve to be the carrier of genetic information in cells as opposed to RNA?

the hydrogen at the 2' position in the deoxyribose of DNA makes it more stable than RNA

In the mismatch repair process, enzyme complexes replace bases that were incorrectly inserted into the newly synthesized DNA strand. To function, they must be able to distinguish between the parent DNA strand and the new strand. How is this accomplished?

the parent strand is methylated