Exam 3- MOL GEN

Group I and group II introns ....... a. exhibit self-excision b. require snRNPs for excision c. form a complex called the splicesome d. are found only in protozoans

A

If one compares the base sequences of related genes from different species, one is likely to find that corresponding ________ are usually conserved, but the sequences of ________ are much less well conserved. A) exons; introns B) introns; exons C) introns; chaperons D) chaperons; exons E) introns; proteins

A

Significant in the deciphering of the genetic code was the discovery of the enzyme polynucleotide phosphorylase. What is this enzyme used for? A) manufacture of synthetic RNA for cell-free systems B) ribosomal translocation C) peptide bond formation D) production of ribosomal proteins E) degradation of RNA

A

When considering the initiation of transcription, one often finds consensus sequences located in the region of the DNA where RNA polymerase(s) binds. Which of the following is a common consensus sequence? A) TATA B) GGTTC C) TTTTAAAA D) any trinucleotide repeat E) satellite DNAs

A

List four base triplets that are clearly responsible for punctuation (initiation, termination).

AUG (rarely GUG) for initiation; UAA, UGA, and UAG for termination

what is the initiator triplet in both pro and eukaryotes? what amino acid is recruited by this triplet?

AUG, methionine

what is the initiator triplet in both pro and eukaryotes? what amino acid is recruited by this triplet?

AUG; methionine

The genetic code is said to be triplet, meaning that there ________. A) are three amino acids per base in mRNA B) are three bases in mRNA that code for an amino acid C) may be three ways in which an amino acid may terminate a chain D) are three "nonsense" triplets E) None of the answers listed is correct.

B

Which of the following two terms relate most closely to split genes? A) 5'-cap, 3'-poly-A tail B) introns, exons C) elongation, termination D) transcription, translation E) heteroduplex, homoduplex

B

Regarding the efficient initiation of transcription by RNA polymerase II, which specific "upstream" signals appear to be involved?

TATA and CAAT base sequences and enhancers

True or False: The code is nonoverlapping, meaning that, assuming "standard translation," a given base participates in the specification of one and only one amino acid.

TRUE

From the late 1950s to the mid-1960s, numerous experiments using in vitro cell-free systems provided information on the nature of the genetic code. Briefly outline significant experiments in the determination of the genetic code.

Use of polynucleotide phosphorylase for the random assembly of nucleotides provided for the assembly of RNA homo- and random heteropolymers, which when placed in the cell-free protein-synthesizing system provided products (polypeptide chains) for analysis. The triplet binding assay along with the use of repeating copolymers was used to verify information provided earlier and to establish the ordered codon assignments.

True or False: Heterogeneous nuclear RNA is a primary transcript in eukaryotes that is processed prior to involvement in translation.

True

in 1964, nirenberg and elder used triplet binding assay to determine codons. a complex of what was trapped in the nitrocellulose filter?

charged tRNA, RNA triplet, and ribosome

The use of homopolymers by Nirenberg and Matthaei permitted four of the 64 possible triplet codons to be assigned. In their experiments, a homopolymer of PolyG led to the incorporation of which amino acid? (you can look up the genetic code table on the right to answer this question). A: Phenylalanine (Phe) B: Proline (Pro) C: Lysine (Lys) D: Glycine (Gly)

d

What was the name of the molecule that Jacob and Monod (1961) postulated carried genetic information from DNA to the site of protein manufacture?

messenger RNA (mRNA)

The finding that virtually all organisms use the same genetic code provides the basis for declaring that the code is universal. Name at least two exceptions to such universality.

mitochondrial DNA, Mycoplasma capricolum, some protozoans

What is meant by the term heterogeneous nuclear RNA (hnRNA)?

pre-mRNA, primary transcripts before processing in eukaryotes

In eukaryotes, which three factors appear to encourage the specific association of RNA polymerase(s) to a specific region of DNA?

promoters, enhancers, and transcription factors

Referring to the genetic code, what is meant by "wobble"?

relaxed pairing specificities in the third-base position of a codon

"Breaking the genetic code" has been referred to as one of the most significant scientific achievements in modern times. Describe (in outline or brief statement form) the procedures used to break the code.

- use of polynucleotide phosphorylase for the production of synthetic mRNAs - introduction of synthetic mRNAs into the cell-free protein-synthesizing system - frameshift mutations in the rII region of T4 phage to show code is triplet and degenerate - triplet binding assay to produce mRNA-tRNA-ribosome complex - development of regular copolymers for use in the cell-free protein-synthesizing system

suppose that in the use of polynucleotide phosphorylase A and C are added in ratio of 1A:5C. what's the probability of AAA?

1/216

Suppose that in the use of polynucleotide phosphorylase, nucleotides A and C are added in a ratio of 1A:5C. What is the probability that an AAA sequence will occur?

1/6 × 1/6 × 1/6

In 1964, Nirenberg and Leder used the triplet binding assay to determine specific codon assignments. A complex of which of the following components was trapped in the nitrocellulose filter? A) ribosomes and DNA B) free tRNAs C) charged tRNA, RNA triplet, and ribosome D) uncharged tRNAs and ribosomes E) sense and antisense strands of DNA

C

RNAs that are capable of splicing themselves are sometimes called A: Ribosomes B: Ribonucleases C: Ribozymes D: Ribotides

C

The genetic code was confirmed by studies using bacteriophage MS2. It was found that the linear sequence of the nucleotides in the bacteriophage genes (and thus the sequence of triplet codons) corresponds precisely with the linear sequence of amino acids in the proteins. Thus the genes and the proteins are said to be....... A: ordered B: complementary C: co-linear D: punctuated

C

When examining the genetic code, it is apparent that ________. A) there can be more than one amino acid for a particular codon B) AUG is a terminating codon C) there can be more than one codon for a particular amino acid D) the code is ambiguous in that the same codon can code for two or more amino acids E) there are 44 stop codons because there are only 20 amino acids

C

There is some indication that the code is in some way ordered; a certain pattern exists. Describe an observation that supports this view.

Certain amino acids may be grouped according to the middle base; for example, U or C in the second position often specifies hydrophobic amino acids. Also, codons with the same two starting letters frequently encode the same amino acid.

What is meant by punctuation in terms of the genetic code?

Certain triplets (AUG) commonly signal the starting point for protein synthesis; other triplets (UAA, UGA, UAG) typically signal stop.

If the C in the codon UAC is mutated to a G, then what will happen? (Use the standard genetic code table to answer this question). A: Tyrosine (tyr) will be replaced with a Tyrosine (A silent mutation) B: Methionine (met) will be replaced with a tyrosine (tyr) C: Valine (val) will be replaced with a stop codon D: Tyrosine (tyr) will be replaced with a stop codon E: None of the above

D

It has been recently determined that the gene for Duchenne muscular dystrophy (DMD) is more than 2000 kb (kilobases) in length; however, the mRNA produced by this gene is only about 14 kb long. What is a likely cause of this discrepancy? A) The exons have been spliced out during mRNA processing. B) The DNA represents a double-stranded structure, whereas the RNA is single-stranded. C) More amino acids are coded for by the DNA than by the mRNA. D) The introns have been spliced out during mRNA processing. E) When the mRNA is produced, it is highly folded and therefore less long.

D

Standard Genetic Code Table AGA UUA AGC AGG UUG AGU GCA CGA GGA CUA CCA UCA ACA GUA GCC CGC GGC AUA CUC CCC UCC ACC GUC UAA GCG CGG GAC AAC UGC GAA CAA GGG CAC AUC CUG AAA UUC CCG UCG ACG UAC GUG UAG GCU CGU GAU AAU UGU GAG CAG GGU CAU AUU CUU AAG AUG UUU CCU UCU ACU UGG UAU GUU UGA Ala Arg Asp Asn Cys Glu Gln Gly His Ile Leu Lys Met Phe Pro Ser Thr Trp Tyr Val STOP A R D N C E Q G H I L K M F P S T W Y V . In a repeating copolymer assay involving A and C, (e.g. ACACACACAC.....) what would you expect to happen ? (use the codon chart to answer this question). A: Threonine (Thr) alone will be incorporated into the protein B: Histidine (His) alone will be incorporated into the protein C: Glutamine (Gln) will be incorporated into the protein D: Threonine and Histidine (Thr, and His) will both be incorporated into the protein E: Threonine and Glutamine (Thr, and Gln) will both be incorporated into the protein

D

What is the initiator triplet in both prokaryotes and eukaryotes? Which amino acid does this triplet recruit? A) UAA; no amino acid called in B) UAA or UGA; arginine C) AUG; arginine D) AUG; methionine E) UAA; methionine

D

It was a surprise to learn in the 1980s that some mRNAs are changed prior to translation so that the mature RNA differs from the sequence encoded in the exons of the DNA. This process, which has mostly been observed in mitochondria and chloroplasts, is referred to as A: RNA splicing B: RNA tailing C: RNA capping D: RNA editing

D: RNA editing

The subunits that provide specificity to the initiation of transcription on different promoters in E. coli are called... A: rho factors B: dNTPs C: cistrons D: Sigma factors

D: Sigma factors

Examples of cis-acting elements in eukaryotes include all of the following except A: TATA box B: CAAT box C: enhancers D: TATA binding protein (TBP)

D: TATA binding protein (TBP)

Introns are known to contain termination codons (UAA, UGA, or UAG), yet these codons do not interrupt the coding of a particular protein. Why? A) UAA, UGA, and UAG are initiator codons, not termination codons. B) Exons are spliced out of mRNA before translation. C) These triplets cause frameshift mutations, but not termination. D) More than one termination codon is needed to stop translation. E) Introns are removed from mRNA before translation.

E

What is the name given to the three bases in a messenger RNA that bind to the anticodon of tRNA to specify an amino acid placement in a protein? A) protein B) anti-anticodon C) cistron D) rho E) codon

E

When scientists were attempting to determine the structure of the genetic code, Crick and coworkers found that when three base additions or three base deletions occurred in a single gene, the wild-type phenotype was sometimes restored. These data supported the hypothesis that ________. A) there are three amino acids per base B) the code contains internal punctuation C) AUG is the initiating triplet D) the code is overlapping E) the code is triplet

E

Which of the following does not happen during hnRNA (heterogenous nuclear RNA) processing? a. a 7-methylguanosine cap is added to the 5' end of the RNA b. introns are spliced out c. a poly Atail is added d. Exons are spliced together e. Ribosomes bind and begin transcription

E

True or False: RNA processing occurs when amino acids are removed from nascent proteins.

False

Sidney Brenner argued that the code was nonoverlapping because he considered that coding restrictions would occur if it were overlapping. A second major argument against an overlapping code involved the effect of a single nucleotide change. In an overlapping code, how many adjacent amino acids would be affected by a point mutation? In a nonoverlapping code, how many amino acid(s) would be affected?

TWO,ONE

Describe how the sigma subunit (factor) of E. coli RNA polymerase participates in transcription.

The sigma subunit may give specificity to the RNA polymerase and play a regulatory function. It may be involved in the recognition of initiation sites or promoters.

If you make mixed copolymers at random using a 2:1 mixture of A:T what % will be AAA... A: About 11% B: About 15% C: About 30% D: About 66%

c

In the genetic code, each triplet specifies only a single amino acid. this means that the genetic code is a. degenerate b. nonoverlapping c. unambiguous d. universal e. none of the above

c

Which amino acid would you expect a tRNA with the anticodon 5'-CAG-3' to carry? Use the standard genetic code table to answer this question. A: Glutamine (Gln) B: Valine (Val) C: Leucine (Leu) D: Lysine (Lys)

c

In a repeating copolymer assay involving A and G, what would you expect to happen ? (use the codon chart below to answer this question). a. Arginine (Arg) will be incorporated into the protein b. Lysine (Lys) will be incorporated into the protein c. Glycine (Gly) will be incorporated into the protein d. All three (Arg, Lys, and Gly) will both be incorporated into the protein e. Arg, Lys, Gly and also Glutamic acid (Glu) will both be incorporated into the protein

e

Which amino acid would you expect a tRNA with the anticodon 5'-GAA-3' to carry ? The standard genetic code table is given below. Standard Genetic Code Table AGA UUA AGC AGG UUG AGU GCA CGA GGA CUA CCA UCA ACA GUA GCC CGC GGC AUA CUC CCC UCC ACC GUC UAA GCG CGG GAC AAC UGC GAA CAA GGG CAC AUC CUG AAA UUC CCG UCG ACG UAC GUG UAG GCU CGU GAU AAU UGU GAG CAG GGU CAU AUU CUU AAG AUG UUU CCU UCU ACU UGG UAU GUU UGA Ala Arg Asp Asn Cys Glu Gln Gly His Ile Leu Lys Met Phe Pro Ser Thr Trp Tyr Val STOP A R D N C E Q G H I L K M F P S T W Y V . a. Lysine (K) b. Glutamate (E) c. Glutamine (Q) d. Leucine (L) e. Phenylalanine (F)

e,b

much of the DNa in eukaryotic genome is non-coding, where is it

eons

In the context of molecular genetics, how does one reconcile the terms overlapping genes and nonoverlapping code?

the genetic code contains codons that are nonoverlapping; however, overlapping genes are observed in some viruses in which, due to differential use of AUG to initiate translation, the same mRNA can yield different protein products.

it has been discovered that the gene for DMD is over 2000 kb, but the mRNA produced is only 17 kb. why?

the introns have been spliced out during mRNA processing

What two experimental procedures allowed deciphering of the ordered triplet assignments of the genetic code?

the triplet binding assay and the use of repeating RNA polymers with known sequence

A base at the first position of an anticodon on the tRNA would pair with a base at the ________ position of the mRNA.

third

a build-in feature of genetic codons is called ____ similar to autocomplete function of typing on your cell phone

wobble position