MicroBio 260: Concept Checks

Binding of an activator to an activator binding site on DNA A. enhances the ability of RNA polymerase to bind to the promoter site. B. binds DNA, RNA and ribosomes together. C. creates a replication fork. D. acts as a primer for RNA synthesis. E. enhances the ability of DNA polymerase to bind to the promoter site.

A

Consider the biochemical pathway: A → B → C Enzyme 1 catalyzes A → B Enzyme 2 catalyzes B → C If enzyme 2 is inactive, which of the following compounds will accumulate? A. B only B. B and C C. A and B D. A only E. C only

A

Coordinated sets of genes that are regulated as a single unit are referred to as ______. A. operons B. exons C. transposons D. plasmids E. introns

A

In some degradative pathways, in the absence of an inducer (such as arabinose), A. the activator protein can't bind to DNA, and RNA polymerase can't bind to the promoter site. B. will block the formation of different types of polyribosome complexes. C. the activator protein can't bind to DNA, and RNA polymerase can't bind to the operator site. D. the activator protein can't compete with the repressor for binding to the operator site. E. the activator protein can't bind to DNA, and DNA polymerase can't bind to the promoter site.

A

In the absence of lactose, A. a repressor protein binds to the operator. Correct B. an activator binds to the operator site of the operon. C. an activator binds to glucose. D. a repressor binds to the activator. E. an inducer binds to the operator site of the operon.

A

Protein synthesis occurs on the ______. A. ribosomes B. cytoplasmic membrane C. mitochondria D. nucleoid E. nuclear membrane

A

Repressible operons (such as the arg operon) A. are usually in the "on" mode. B. are turned off by low levels of nutrients. C. are usually in the "neutral" mode. D. are usually in the "off" mode. E. are only turned off when the nutrient is required.

A

The lac operon is expressed when: A. glucose is low and lactose is present. glucose is low, regardless of the presence or absence of lactose. glucose is low and lactose is absent. glucose is high and lactose is absent. glucose is high and lactose is present.

A

Two different mechanisms for copying the DNA strands are used because A. the strands are oriented in opposite directions. repressor proteins bind to one strand. primase is needed on one strand but not the other. purines and pyrimidines require different enzymes. of changing levels of free nucleotides during the process.

A

When an amino acid such as arginine binds to a repressor, A. the repressor binds to the operator site. Correct B. the repressor binds to an allosteric site on an activator. C. the repressor binds to the small ribosomal subunit. D. the repressor gets completely degraded. E. the repressor detaches from the operator site.

A

Which nucleotide is not found in RNA? A. Thymine Uracil Guanine Adenine Cytosine

A

Which of these is base-paired correctly? A. T - A B. C - T C. G - T D. T - T E. C - A

A

DNA polymerase holds the double helix together. B. requires a template for the synthesis of DNA. can add nucleotides in two different directions. can work with both single-stranded and double-stranded DNA. fills in gaps between DNA fragments.

B

If an organism lost the ability to make primase, what would it be unable to do? A. Add a short sequence of complementary RNA to the existing DNA strand. Unwind the template DNA at the origin of replication. Supercoil DNA after replication is complete. Rewind the template DNA at the origin of replication. Add a short sequence of complementary DNA to the existing DNA strand.

B

In the absence of lactose, the lac repressor is: A. inactive and can bind to the operator. B. active and can bind to the operator. C. active and cannot bind to the operator. D. inactive and cannot bind to the operator. E. inactive and cannot bind to the promoter.

B

On one of the strands of bacterial DNA, the new complementary strand is synthesized discontinuously in small pieces of DNA called ______. introns B. Okazaki fragments primers spliceosomes lagging fragments

B

RNA is a chain of ______. nucleic acids B. nucleotides monosaccharides proteins amino acids

B

The specific point on the DNA molecule where replication begins is the start. B. origin of replication. R factor. hinge region. poly-A tail.

B

The three basic parts of a DNA nucleotide are: A. carboxyl group, deoxyribose sugar, nitrogenous base. B. phosphate, deoxyribose sugar, nitrogenous base. Correct C. phosphate, deoxyribose sugar, glycerol. D. phosphate, hexose sugar, nitrogenous base. E. phosphate, deoxyribose sugar, phospholipid.

B

What component of RNA is different from one person (or one bacterium) to the next? The number of phosphates. B. The order of nitrogenous bases. Nothing. They are the same. The type of pentose sugar. The bond between the phosphate and sugar.

B

When a bacterium is grown on glucose only, A. it can only synthesize carbohydrates and must make proteins via catabolism. B. it must synthesize all the amino acids it needs. Correct C. it will be unable to synthesize lipids. D. it must respire anaerobically. E. it must synthesize about half of the amino acids it needs.

B

Why is translation needed? A. The enzymes involved in nucleic acid synthesis are different from those involved in protein synthesis. B. The subunits of nucleic acids are nucleotides, while those of proteins are amino acids. C. The subunits of nucleic acids are amino acids, while those of proteins are nucleotides.

B

A hydrogen atom consists of: electrons only. a variable number of protons and electrons. a proton and an electron. protons only. a proton and several electrons

C

A segment of DNA encoding a protein or an RNA molecule is a ______. A. genus B. phenotype C. gene D. chromosome E. genotype

C

Consider the biochemical pathway: A → B → C Enzyme 1 catalyzes A → B Enzyme 2 catalyzes B → C Enzyme 1 can use A. only B as a substrate. B. both A and B as substrates. C. only A as a substrate. D. either A or B as substrate, but not both. E. neither A nor B as substrate.

C

If the codon GGU is positioned in the A site of the ribosome, which of the following will occur? A. A tRNA with the anticodon CCT will add its amino acid to the peptide chain. B. The ribosomal complex will dissociate and release the peptide chain. C. A tRNA with the anticodon CCA will deliver its amino acid to the site. D. An mRNA with the anticodon CCT will add its amino acid to the peptide chain. E. The mRNA will exit the E site to prepare for another incoming amino acid.

C

In an inducible operon, when a substrate or inducer is present, A. it reacts with the operator and inactivates it. B. it reacts with the repressor and activates it. C. it reacts with the repressor and inactivates it. Correct D. it reacts with the operator and activates it. E. it reacts with the repressor and activates the operator.

C

One bacterial chromosome replicates to become two chromosomes with each made of alternating 1000 bp stretches of original and newly synthesized DNA. each made entirely of newly synthesized DNA after the original is enzymatically degraded. C. each made of one strand of DNA from the original chromosome and one newly synthesized strand. each made of one strand of DNA from the original chromosome and one RNA strand. one of which contains the original DNA and one of which is made entirely of newly synthesized DNA.

C

The two strands of DNA are joined to each other or held together by: A. covalent bonding. B. Van der Waals forces. C. hydrogen bonding. D. J-chains. E. hydrophilic interaction.

C

Transcription begins when RNA polymerase binds to the RNA primer. terminator on DNA. C. promoter on DNA. initiator on DNA. promoter on RNA.

C

What role does the sigma factor of RNA polymerase have in transcription? It recognizes and binds to the promoter region of the template RNA. It recognizes and binds to the terminator sequence of the template DNA. C. It recognizes and binds to the promoter region of the template DNA. It synthesizes a primer used by the RNA polymerase to recognize the template DNA. It makes a complementary RNA copy of the DNA template.

C

Which of the following correctly describes the pairing and hydrogen bonding of nucleobases in DNA? A. Adenine pairs with thymine via three hydrogen bonds; cytosine pairs with guanine via two hydrogen bonds. B. Adenine pairs with cytosine via two hydrogen bonds; guanine pairs with thymine via three hydrogen bonds. C. Adenine pairs with thymine via two hydrogen bonds; cytosine pairs with guanine via three hydrogen bonds. D. Adenine and guanine pair with three hydrogen bonds; cytosine and thymine pair with two hydrogen bonds. E. Adenine and thymine can pair with either cytosine or guanine via two hydrogen bonds.

C

Cells obtain energy by ______ food molecules such as glucose. A. phosphorylating B. anabolizing C. redoxing D. oxidizing E. reducing

D

The initial transfer RNA occupies the _____ site on the ribosome. A. X site B. E site C. A site D. P site E. F site

D

The process of transcription is similar to: A. the synthesis of the lagging strand during DNA replication. B. division by binary fission in prokaryotes. C. division by mitosis in eukaryotes. D. the synthesis of the leading strand during DNA replication. E. the synthesis of proteins by translation.

D

When a repressor binds to the operator site on DNA, A. it prevents the binding of the substrate to the operator site. B. it links adjacent thymines and alters DNA folding. C. it prevents the binding of the substrate to the repressor site. D. it blocks RNA polymerase binding and mRNA synthesis. E. the operator site forms a hairpin loop with the structural locus.

D

A ______ is the physical expression of the genes present and can change depending upon what genes are turned "on". A. chromosome B. phenogene C. genotype D. plasmid E. phenotype

E

A mechanism that blocks transcription A. will block ribosomes from producing protein. B. will block mRNA from binding to ribosomes. C. will prevent the synthesis of a new DNA molecule. D. blocks passage of mRNA out of the nucleus. E. will block the production of mRNA.

E

After mRNA is made, what generally occurs? A. It is degraded. B. It is transcribed again. C. It is translated to DNA. D. It is converted into protein. E. It is translated to protein.

E

DNA polymerase: unwinds the helix and separates the two strands. synthesizes both new strands continuously. synthesizes a short fragment of RNA to initiate replication. "stitches" the Okazaki fragments together. E. can only add nucleotides in a certain direction.

E

Early in the process of DNA replication, the enzyme ______ separates the two strands. primase replicase polymerase endonuclease E. helicase

E

Enzymes are usually ______. A. steroids B. carbohydrates C. nucleic acids D. lipids E. proteins

E

If one strand of DNA contains the bases ACAGT, what would be the complementary bases on the mRNA strand? UCUGA TGTCA GUGAC ACAGT E. UGUCA

E

One advantage of having genetic control mechanisms is: A. the chance of mutations during RNA synthesis is reduced. B. free nucleotides are not used up too rapidly. C. too many sections of the DNA molecule are not used at the same time. D. the information in introns can be conserved. E. enzymes are only produced when they are needed.

E

Synthesis of mRNA is in the 3' to 5' direction with new nucleotides being added to the 5' end of the mRNA molecule. in the 5' to 3' direction with new nucleotides being added to the 5' end of the mRNA molecule. initiated at the origin of replication. carried out by the enzyme DNA polymerase. E. in the 5' to 3' direction with new nucleotides being added to the 3' end of the mRNA molecule.

E

The two strands of the DNA molecule are ______. A. reversed B. alternating C. parallel D. identical E. antiparallel

E

Translation is needed because: A. the subunits of DNA and RNA are nucleotides while those of protein are nucleic acids. B. the subunits of DNA and RNA are nucleotides while those of protein are polysaccharides. C. the subunits of DNA and RNA are nucleic acids while those of protein are amino acids. D. the subunits of DNA and RNA are amino acids while those of protein are nucleotides. E. the subunits of DNA and RNA are nucleotides while those of protein are amino acids.

E

What does the word "transcribe" mean? To make a complement. To initiate. To delete a copy. To replicate. E. To make a copy.

E

What happens when a hairpin loop forms in mRNA? Transcription of the coding strand begins. Exons are removed from the RNA transcript. Transcription of DNA to mRNA begins. The RNA polymerase and the mRNA bind tighter to the DNA. E. The RNA polymerase and the mRNA dissociate from the DNA.

E

What three components make up RNA subunits? Amino acid, phosphate, nitrogenous base. Adenosine, two phosphates. Phosphate, polymerase, ribose sugar. Phosphate, nitrogenous base, deoxyribose sugar. E. Phosphate, nitrogenous base, ribose sugar.

E

What usually terminates the process of translation? Depleted tRNA supply. Presence of a repeating mRNA sequence. Ribosome degradation with use. Presence of a terminator on mRNA. E. Presence of a stop codon on mRNA.

E

Which of the following best describes the structure of DNA? A. A double helix consisting of two sugar-phosphate backbones with nucleobases oriented towards the exterior. B. A triple helix consisting of three sugar-phosphate backbones with nucleobases oriented towards the interior. C. A double helix consisting of two chains of nucleobases with sugar-phosphate connections holding them together. D. A double helix consisting of two chains of alternating sugar, phosphate, and nucleobases, held together by covalent bonds. E. A double helix consisting of two sugar-phosphate backbones with nucleobases oriented towards the interior.

E

Which of the following binds to the active site of an enzyme? A. Another enzyme B. ATP C. Product D. Water E. Substrate

E

All biochemical pathways have the same number of enzymatic reactions. True/False

False

An enzyme can only bind one substrate at a time. True/False

False

An enzyme speeds up a chemical reaction in the cell, but can only be used once. True/False

False

The purpose of RNA synthesis is to provide a new copy of DNA as the original strand deteriorates over time. True/False

False

Which of the following statements accurately describe biochemical pathways? Choose all that apply. They convert an initial substrate through a series of steps into an end product. They are well-organized and structured. They can be linear, branched, or cyclical. They are carefully regulated. They always run at their maximum rate. They proceed at a constant rate. They only function for a few times.

Pink True

Doubled-stranded DNA consists of two antiparallel strands, meaning that one strand is oriented in the 5' to 3' direction, while the other is oriented in the 3' to 5' direction. True/False

True

In a biochemical pathway, the product of the first reaction becomes the substrate in the second reaction. True/False

True

Replication, transcription and translation take place in the bacterial cytoplasm. True/False

True

The energy captured in the phosphorylation of ADP to ATP comes from the proton motive force created in respiration. True/False

True

Unlike DNA, RNA is usually single-stranded. True/False

True

Whenever a molecule is oxidized, another molecule must be reduced. True/False

True