Bio 301 - Midterm 2

Use the genetic code shown in Figure 7-25, page 239, to identify which of the following nucleotide sequences would code for the polypeptide sequence arginine-glycine-aspartate (RGD):

5'-AGA-GGA-GAU-3'

Which of the following statements is false?

A mutation that arises in a mother's somatic cell often causes a disease in her daughter.

RNA processing steps that take place in the nucleus include ___________________________.

A, B, and C occur in the nucleus prior to mRNA export to the cytoplasm.

Viral genomes _________.

ALL OF THE ABOVE ARE TRUE (-can be made of DNA or RNA can be either double-stranded or single-stranded).

RNA can function in the following way (s):

All of the above are correct.

The bonds that form between the anticodon of a tRNA molecule and the three nucleotides of a codon in mRNA are _________________.

B and C

Which of the following statements about RNA interference (or RNAi) is false?

Because RNAi depends on the introduction of a double-stranded RNA into a cell or an organism, it is not a process that can cause heritable changes in gene expression.

DNA ligase is an enzyme used when making recombinant DNA molecules in the lab. In what normal cellular process is DNA ligase involved?

DNA replication

Unlike soluble, cytosolic proteins, membrane proteins are more difficult to purify. Which of the following substances is most commonly used to help purify a membrane protein?

Detergent

RNA-induced silencing complex (RISC) can bind to specific RNAs present in the cytoplasm of a cell that are complementary to the small RNA that the RISC carries. Which of the following statements is incorrect?

Dicer is a nuclease that cleaves double stranded DNA into short fragments. - NOT DNA but RNA

T/F "Since introns do not contain protein-coding information, they do not have to be removed precisely (meaning, a nucleotide here and there should not matter) from the primary transcript during RNA splicing."

FALSE

F/T "Proteins that are degraded in the cytosol are tagged with ubiquitin molecules that are recognized by proteins that make up the proteasome. These proteins bind the ubiquitin tagged proteins and feed them into the proteasome, which is lined with proteases that digest the tagged protein. This is the only point in gene expression that is not regulated."

False

T/F "All mRNAs fold into particular three-dimensional structures that are required for their translation."

False

T/F "An individual ribosome can make only one type of protein."

False

T/F "Because the two strands of DNA are complementary, the mRNA of a given gene can be synthesized using either strand as a template."

False

T/F "Ribosomes are cytoplasmic organelles that are encapsulated by a single membrane."

False

T/F "The amount of a protein present in the cell depends on its rate of synthesis, its catalytic activity, and its rate of degradation."

False

T/F "The large and small subunits of an individual ribosome always stay together and never exchange partners."

False

T/F "There is little conserved synteny between human and mouse genes."

False

True or False:The increased complexity of humans compared with flies and worms is largely due to the vastly larger number of genes in humans.

False

T/F "An mRNA may contain the sequence 5'-TTATTGACCCCGGTTCAATT-3'."

False - Uracil

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.

Which of the following statements is false?

Genes that code for ribosomal RNA share significant similarity in all eukaryotes but are much more difficult to recognize in archaea.

Which amino acid would you expect a tRNA with the anticodon 5′-CUU-3′ to carry?

LYSINE - 5'-CUU-3' -> 3'-AAG-5' = Lysine (corresponding codons and in the 3 to 5' direction)

Imagine that you have created a fusion between the TRP operon, which encodes the enzymes for tryptophan biosynthesis, and the LAC operon, which encodes the enzymes necessary for lactose utilization in which the LAC regulatory region is missing. Under which of the conditions will lactose-related genes be expressed in the strain that carries the fused operons?

Only when tryptophan is absent

Which of the following statements about PCR is false?

PCR is particularly powerful because after each cycle of replication, there is a linear increase in the amount of DNA available. -It is NOT linear

Which of the following type of mutation would be predicted to be most harmful to an organism?

REMOVAL of a single NUCLEOTIDE near the BEGINNING of the CODING SEQUENCE

Like DNA, _____________ is a linear polymer made of four different types of nucleotide subunits linked together by phosphodiester bonds.

RNA

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 ___________________.

RNA is single-stranded.

Transcription in bacteria differs from transcription in a eukaryotic cell because _________________________.

RNA polymerase (along with its sigma subunit) can initiate transcription on its own.

Which of the following statements about restriction nucleases is false?

Restriction nucleases recognize specific sequences on single-stranded DNA.

Red blood cells have been very useful in the study of membrane proteins and the protein components that provide structural support. Which of the following is the principal fibrous protein in the cortex of RBCs?

Spectrin

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?

The ribosome binds to the mRNA

Porin proteins form large, barrel-like channels in the membrane. Which of the following is NOT true about these channels?

They are made primarily of α helices

The central dogma of biology states that DNA to RNA to Protein. The first step of the process is called ____ and the second step of the process is known as______ .

Transcription, translation

T/F "Although all of the steps involved in expressing a gene can in principle be regulated, for most genes, the initiation of transcription is the most important point of control."

True

T/F "Cells in multicellular organisms have mechanisms that enable their progeny to 'remember' what type of cell they should be. One example of such a mechanism is a positive feedback loop for the expression of a transcription factor that regulates its own transcription."

True

T/F "Genetic changes that offer an organism a selective advantage or those that are selectively neutral are the most likely to be perpetuated. Changes that seriously compromise an organism's fitness are eliminated through natural selection."

True

T/F "Genetic changes that provide a selective advantage are likely to be preserved in a population over time."

True

T/F "Many transcription factors that function as gene repressors do so by attracting histone deacetylases to a specific location on the chromatin, while many transcription factors that function as gene activators do so by recruiting histone acetylases to the specific location on the chromatin. "

True

T/F "MicroRNAs (miRNAs) control gene expression by base pairing with specific mRNAs and regulating their stability and their translation."

True

T/F "Only a few percent (1-2%) of the human genome codes for proteins."

True

T/F "Post-transcriptional controls operate after RNA polymerase has bound to a gene's promoter and started to synthesize RNA."

True

T/F "Prokaryotes coordinate the expression of several genes by having the genes clustered together in an operon."

True

T/F "RNA is a single stranded molecule, while DNA is found as a double helix in cells. This allows RNA to fold into many different three dimensional structures that are not possible for DNA."

True

T/F "RNA polymerases are the enzymes that catalyze the process of transcription."

True

T/F "Riboswitches are sequences within self-regulating mRNAs that change their conformation when bound to small molecules such as metabolites."

True

T/F "Single-nucleotide polymorphisms (SNPs) are sequences in the genome that differ by a single nucleotide pair between one portion of the population and another. "

True

T/F "The bulk of the human genome is made of noncoding and repetitive nucleotide sequences. This is due in part to the mobile genetic elements that have multiplied by replicating themselves and inserting new copies in different locations within the genome."

True

T/F "The stepwise linking of amino acids into a polypeptide chain is catalyzed by an rRNA molecule in the large ribosomal subunit. Therefore, the ribosome is an example of a RIBOZYME, an RNA molecule that can catalyze a chemical reaction."

True

T/F "snRNPs (snurps) are composed of proteins and small nuclear RNAs (snRNA) which together coordinate the removal of introns and the joining of exons to form the mature mRNA."

True

Which of the following statements is false?

Unlike DNA, RNA uses a uracil base and a deoxyribose sugar. - not deoxyribose but just a RIBOSE sugar

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 Q7-45. 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

Maintaining cell type can be accomplished by ____________.

all of the above

RNA differs from DNA in the following respect (s):

all of the above are correct.

In control of bacterial gene transcription, a repressor protein binds to

an operator

The expression of the TRP operon in E. coli is regulated in part by the availability of the amino acid tryptophan. The regulation of the TRP operon is a process referred to as

attenuation by a repressor

Which of the following sequences of events occurs when E. coli cells are released from catabolite repression by transfer to a very low-glucose environment?

cAMP levels rise, cAMP binds to CAP, cAMP-CAP complex binds to a site on DNA and activates transcription.

New membrane phospholipids are synthesized by ______ enzymes bound to the side of the _________ _______ membrane.

cytosolic, endoplasmic reticulum

Formation of 5-methylcytosine occurs by methylation of a cytosine base in the DNA double helix. In vertebrates this event is confined to selected cytosines that fall next to a guanine. This mechanism of transmission of information from parent to daughter cell is a form of _____________.

epigenetic inheritance

Genetic variation in a population can arise over time through 1) mutation within a gene, 2) mutation within the regulatory DNA of a gene, 3) gene duplication, 4) exon shuffling, 5) horizontal gene transfer within the _______________.

germ cells

In eukaryotic cells, there are multiple types of RNA polymerases. RNA polymerase I is responsible for transcription of most ribosomal RNAs, while RNA polymerase III is responsible for the polymerization of tRNAs, the small 5S ribosomal RNA, and some other small RNAs. RNA polymerase II transcribes genes that encode__________________.

proteins, miRNAs, and small RNAs required for splicing

The sigma subunit of bacterial RNA polymerase ___________________.

recognizes promoter sites in the DNA.

With fully automated Sanger sequencing, all four chain-terminating ddNTPs can be added into a single reaction. This is different from the traditional slab gel Sanger sequencing, where a different reaction had to be carried out for each ddNTP. The mixing of all four ddNTPs can be carried out because ______________.

the fully automated Sanger sequencing reactions generate a set of products, each of which carries a single fluorescent tag whose color reveals the identity of the base that is at the end of the product.

A neuron and a white blood cell have very different functions. For example, a neuron can receive and respond to electrical signals while a white blood cell defends the body against infection. This is because ______.

the neuron expresses some mRNAs that the white blood cell does not.

The mechanism by which cells copy DNA into RNA is called _______________.

transcription

__________ match amino acids to codons in the mRNA.

transfer (tRNA)

_____ match anticodons to codons in the mRNA.

transfer RNA (tRNA)

The conversion of the information in RNA into protein is referred to as ___________ wherein the information in the RNA is expressed in nucleotide sequence and the information in protein is expressed in amino acid sequence.

translation

General transcription factors are required for RNA polymerase II to initiate transcription in eukaryotic cells. The general transcription factor ________________ binds to a short double-helical DNA sequence primarily composed of T and A nucleotides, known as the TATA sequence or the 'TATA box'. The TATA box is located 25 nucleotides upstream fro the transcription start site of a gene.

TFIID

The distinct characteristics of different cell types in a multicellular organism are produced mainly by the differential regulation of the

TRANSCRIPTION of genes transcribed by RNA POLYMERASE II.

Which one of the following is the main reason that a typical eukaryotic gene is able to respond to a far greater variety of regulatory signals than a typical prokaryotic gene or operon?

The TRANSCRIPTION of a eukaryotic gene can be INFLUENCED by MANY PROTEINS binding ENHANCERS and SILENCERS far from the promoter.

Your muscle and bone cells are different because

different genes are switched on and off in each type of cell.

DNA binding proteins most often bind to the DNA helix at the ___________ groove of the DNA. DNA binding proteins contain a special motif, or shape, that allow them to bind to the DNA. For instance, a _________ is a DNA binding protein that binds to the DNA as a dimer stabilized by hydrophobic interactions.

major, leucine zipper

In eukaryotic cells, ____________ carry the information transcribed from just one gene, coding for a single protein.

messenger RNA (mRNA)

The specific sequence of nucleotides that indicates the starting point for RNA synthesis is contained within the __________.

promoter