bio hw

What is the nuclear pore complex?

A pore complex that regulates transport of specific large molecules (exports material between the nucleus and the cytoplasm)

CH7: Transcription of a gene produces an RNA complementary to one strand of DNA. Fill in the letters A and B with the phrases that best fit the description. A) template strand B) coding strand A) coding strand B) template strand A) top strand B) bottom strand A) 5' strand B) 3' strand

A) coding strand B) template strand

Enzymes:

Catalyze covalent bond breakage or formation

Enzymes in the enzyme class "kinase":

Catalyze the addition of phosphate groups to molecules

An example of a disease caused by prions is:

Creutzfeldt-Jakob disease

(Q048) You have discovered an alien life-form that surprisingly uses DNA as its genetic material, makes RNA from DNA, and reads the information from RNA to make protein using ribosomes and tRNAs, which read triplet codons. Because it is your job to decipher the genetic code for this alien, you synthesize some artificial RNA molecules and examine the protein products produced from these RNA molecules in a cell-free translation system using purified alien tRNAs and ribosomes. You obtain the results shown in Table 7-48. From this information, which of the following peptides can be produced from poly UAUC?

Cys-Pro-Lys-Ala FEEDBACK: All other answers are not possible, because poly UAUC cannot code for Tyr. Tyr must be encoded by AUA, because both poly AUA and poly UA lead to the synthesis of Tyr.

True or false: RNA polymerase II can begin transcription alone

False

True or false: prokaryotic transcription regulators may recruit histone acetyltransferases or histone deacetylases to initiate or inhibit transcription

False, it inhibits but does not initiate

In a chain of enzymatic reactions ______________ reduces the activity of an enzyme early in the pathway.

Feedback inhibition

CH7: (Q021) Which of the following statements about RNA splicing is FALSE?

For a gene to function properly, every exon must be removed from the primary transcript in the same fashion on every mRNA molecule produced from the same gene.

Accessory proteins that assemble at the promoter of a eukaryotic gene and help position RNA polymerase are known as:

General Transcription Factors

What protein is expressed in all cell types in a human body?

Housekeeping proteins

The purpose of using both primary antibodies and labeled secondary antibodies to detect an antigen is to:

Increase the signal, allowing smaller numbers of antigen molecules to be detected.

Ch7: (Q022) Genes in eukaryotic cells often have intronic sequences coded for within the DNA. These sequences are ultimately not translated into proteins. Why?

Intronic sequences are removed from RNA molecules by the spliceosome, which works in the nucleus.

What does RNA polymerase II do?

It synthesizes mRNA in eukaryotes

What does RNA polymerase I do?

It synthesizes rRNA in the nucleus in eukaryotes

What does RNA polymerase III do?

It synthesizes tRNA in the nucleus in eukaryotes

(Q042) Which of the following statements about the proteasome is FALSE? A. Ubiquitin is a small protein that is covalently attached to proteins to mark them for delivery to the proteasome. B. Proteases reside in the central cylinder of a proteasome. C. Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold. D. The protein stoppers that surround the central cylinder of the proteasome use the energy from ATP hydrolysis to move proteins into the proteasome inner chamber.

Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold. FEEDBACK: Once proteins are sent to the proteasome, proteases degrade them. Chaperone proteins provide a place for misfolded proteins to attempt to refold.

CH7: Which of the following statements is FALSE? -RNA polymerase can start making a new RNA molecule without a primer; DNA polymerase cannot. -RNA polymerase does not proofread its work; DNA polymerase does. -RNA polymerase catalyzes the linkage of ribonucleotides while DNA polymerase catalyzes the linkage of deoxyribonucleotides. -RNA polymerase adds bases in a 3´-to-5´ direction; DNA polymerase adds bases in a 5´-to-3´ direction.

RNA polymerase adds bases in a 3´-to-5´ direction; DNA polymerase adds bases in a 5´-to-3´ direction.

CH8: (Q045) Ribozymes are known to catalyze which of the following reactions in cells?

RNA splicing

chapter8: (Q038) Which of the following statements about prokaryotic mRNA molecules is FALSE?

Ribosomes must bind to the 5´ cap before initiating translation.

Segments of a protein that form structures such as an α-helix or β-sheet is the:

Secondary Structure

Fill in the blank. Bacterial RNA polymerase contains a subunit called __factor that recognizes the promoter of a gene.

Sigma

Take a look at this image that represents DNA replication along with the "end-replication problem," and then select the statement that is TRUE.

Telomerase activity would solve the end-replication problem, as this enzyme is involved in telomere lengthening.

CH7: Select all that apply. Which of the following is true about RNA? -The 2' carbon on the ribose sugar is oxygenated -The 2' carbon on the ribose sugar is deoxygenated -RNA contains the nucleotide Uracil -RNA contains the nucleotide Thymine

The 2' carbon on the ribose sugar is oxygenated RNA contains the nucleotide Uracil

CH7: (Q017) You have a bacterial strain with a mutation that removes the transcription termination signal from the Abd operon. Which of the following statements describes the most likely effect of this mutation on Abd transcription?

The Abd RNA from the mutant strain will be longer than normal.

Gene expression in eukaryotic cells can be controlled at 7 different steps. Which of these occur in the nucleus?

Transcription control and RNA processing control

True or false: many proteins require various modifications to become fully functional

True

Antibodies are made of:

Two identical heavy chains and two identical light chains

A "disulfide bond" describes a covalent bond between:

Two sulfur atoms

In an aqueous solution, which amino acid will orient itself inside the center of the protein?

Valine

RNAs that remain behind the nucleus for degradation are known as?

Waste RNA

CH7: (Q002) RNA in cells differs from DNA in that

it is single-stranded and can fold up into a variety of structures.

CH7: What is the function of the replication protein known as the sliding clamp?

keeps DNA polymerase firmly attached to the template while it is synthesizing new strands of DNA

Based on your knowledge of the chemistry of the cell membrane, which of the following compounds would you couple with a new drug in order to achieve better uptake by cells?

lipids

(Q030) Which amino acid would you expect a tRNA with the anticodon 5´-CUU-3´ to carry?

lysine

What gets sent out of the nucleus for translation? mRNA or pre-mRNA?

mRNA

Chapter 8: (Q044) According to current thinking, the minimum requirement for life to have originated on Earth was the formation of a

molecule that could catalyze its own replication.

Ch8: (Q037) In eukaryotes, but not in prokaryotes, ribosomes find the start site of translation by

scanning along the mRNA from the 5´ end.

What protein is responsible for carrying out RNA spicing?

snRNA

What can be said about feedback loops?

-A system CANNOT have feedback inhibition AND positive regulation working together in one system -Feedback inhibition refers to prevention of enzymes from acting -Positive regulation refers to stimulated enzymatic activity

The core repeating sequence of the polypeptide backbone is:

-N-C-C-

Which of the following is true regarding hemoglobin?

-One molecule of hemoglobin contains 4 noncovalent bound heme groups -One molecule of hemoglobin contains heme groups with a single central Iron atom -One molecule of hemoglobin contains heme groups with a single central Iron atom -hemoglobin binds reversibly to dissolved oxygen gas

What is true regarding Phosphorylation?

-Protein Kinases are responsible for attaching phosphate groups to proteins -Phosphorylation is utilized in order to control the activity of many types of proteins in eukaryotic cells -The addition/removal of phosphate groups from specific protein are often a result of cell signaling

How many different possible sequences could you have of a protein that is four amino acids long?

160,000

The cells of a multi-cellular organism contain the same genetic instructions, yet a typical differentiated cell expresses about what percent of total genes in its repertoire?

50%

CH7: (Q012) You have a piece of DNA that includes the following sequence:5´-ATAGGCATTCGATCCGGATAGCAT-3´3´-TATCCGTAAGCTAGGCCTATCGTA-5´ Which of the following RNA molecules could be transcribed from this piece of DNA?

5´-AUAGGCAUUCGAUCCGGAUAGCAU-3´

CH7: (Q009) Which of the following molecules of RNA would you predict to be the most likely to fold into a specific structure as a result of intramolecular base-pairing?

5´-CCCUAAAAAAAAAAAAAAAAUUUUUUUUUUUUUUUUAGGG-3´

Which of the following is true about RNA polymerase? A. Catalyzes the formation of the phosphodiester bonds that link the nucleotides together and form the sugar-phosphate backbone of the RNA chain B. The RNA polymerase moves stepwise along the DNA, unwinding the DNA helix just ahead to expose a new region of the template strand for complementary base-pairing C. the growing RNA chain is extended by one nucleotide at a time in the 5′-to-3′ direction D. The incoming ribonucleoside triphosphates (ATP, CTP, UTP, and GTP) provide the energy needed to drive the reaction forward

All

Which of the following mechanisms allow for one gene to code for multiple gene products?

Alternative splicing

What is the role of aminoacyl tRNA synthetase?

Aminoacyl tRNA synthetase catalyzes the charging reaction that links a specific amino acid to a tRNA molecule.

In an SDS-PAGE, proteins migrate toward the:

Anode

(Q047) When using a repeating trinucleotide sequence (such as 5´-AAC-3´) in a cell-free translation system, you will obtain...?

Answer: three different types of peptides, each made up of a single amino acid. FEEDBACK: An mRNA composed of a trinucleotide repeat of AAC can be "read" in three different frames: AAC, ACA, and CAA. Thus, this mRNA will yield polyasparagine (codon = AAC), polythreonine (codon = ACA), and polyglutamine (codon = CAA).

What does an antibody recognize as its target?

Antigens

CH7: In DNA replication, which of the following events happens during leading strand synthesis but not during lagging strand synthesis?

DNA polymerase synthesizes a single, continuous strand of DNA

The most common covalent cross-links in proteins are?

Disulfide bonds

Before a mature mRNA passes through the nuclear pore complex "gate" between the nucleus and cytosol, it must first be modified by,

Exon junction complexes, poly-A binding proteins, and a cap-binding complex

CH8: (Q041) Which of the following methods is not used by cells to regulate the amount of a protein in the cell? A. Genes can be transcribed into mRNA with different efficiencies. B. Many ribosomes can bind to a single mRNA molecule. C. Proteins can be tagged with ubiquitin, marking them for degradation. D. Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm.

Nuclear pore complexes can regulate the speed at which newly synthesized proteins are exported from the nucleus into the cytoplasm. FEEDBACK: Proteins are synthesized in the cytoplasm and therefore newly synthesized proteins would not be exported from the nucleus into the cytoplasm.

Mature mRNA is transported from the ___ to the ___ through the nuclear pore complex?

Nucleus, cytosol

The amino acid sequence of a protein is the:

Primary Structure

A complex of multiple polypeptide chains is known as the

Quaternary Structure

(Q046) You are studying a disease that is caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA. Which of the following molecules are likely to contain the genetic information of the virus? A. RNA B. Lipids C. Carbohydrates D. High-Energy Phosphate Groups

RNA

CH8: (Q043) Which of the following molecules is thought to have arisen first during evolution?

RNA

CH7: Telomeres serve as caps protecting the ends of linear chromosomes. Which of the following is FALSE regarding the replication of telomeric sequences?

The leading strand doubles back on itself to form a primer for the lagging strand.

Ch8: (Q039) You have discovered a protein that inhibits translation. When you add this inhibitor to a mixture capable of translating human mRNA and centrifuge the mixture to separate polyribosomes and single ribosomes, you obtain the results shown in Figure 7-39. Which of the following interpretations is consistent with these observations?

The protein binds to sequences in the 5´ region of the mRNA and inhibits the rate of initiation of translation.

Which of the following is considered True? A. The replication fork is asymmetrical B. Okazaki fragments proofread and correct for nucleotide mismatches C. Primase is an example of a DNA polymerase D. Ligase unwinds the DNA helix

The replication fork is asymmetrical

CH7: (Q019) Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?

The ribosome binds to the mRNA.

Q033) A strain of yeast translates mRNA into protein inaccurately. Individual molecules of a particular protein isolated from this yeast have variations in the first 11 amino acids compared with the sequence of the same protein isolated from normal yeast cells, as listed in Figure 7-33. What is the most likely cause of this variation in protein sequence?

a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different amino acids FEEDBACK: A mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between amino acids would allow an assortment of amino acids to be attached to the tRNAIle. These assorted aminoacyl-tRNAs would then base-pair with the isoleucine codon and cause a variety of substitutions at positions normally occupied by isoleucine. A mutation in the gene encoding the protein would cause only a single variant protein to be made. A mutation in the anticodon loop of tRNAIle or a mutation in the isoleucyl-tRNA synthetase that decreases its ability to distinguish between different tRNA molecules would cause the substitution of isoleucine for some other amino acid (which is the opposite of what is observed).

CH7: What are DNA topoisomerases responsible for?

relieve the tension that builds up in front of a replication fork

What is a replication bubble?

an unwound and open region of a DNA helix where DNA replication occurs. Usually around low energy level areas like TATA sequences

chapter 8: (Q029) The piece of RNA below includes the region that codes for the binding site for the initiator tRNA needed in translation. 5´-GUUUCCCGUAUACAUGCGUGCCGGGGGC-3´ Which amino acid will be on the tRNA that is the first to bind to the A site of the ribosome?

arginine

CH7: What is the function of mRNA?

code for proteins

What is the product of transcription before splicing takes place?

pre-mRNA

CH7: (Q014) The sigma subunit of bacterial RNA polymerase

recognizes promoter sites in the DNA.

chapter 8: (Q040) The concentration of a particular protein, X, in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal. Which of the following mutations in the gene for X could explain these results?

the deletion of a sequence that encodes sites at which ubiquitin can be attached to the protein