Mastering Chapter 17: Gene Expression

A _______ mutation causes a wild-type amino acid to be replaced by a different amino acid.

missense

During RNA processing a(n) _______ is added to the 5' end of the RNA.

modified guanine nucleotide

A ________ mutation causes an early Stop codon to occur.

nonsense

A _______ mutation does not change the wild-type amino acid sequence.

silent

The anticodon of a particular tRNA molecule is...

...complementary to the corresponding mRNA codon

The direction of synthesis of an RNA transcript is _______.

5' -> 3'

Which of the following is true of a codon?

It can be either in DNA or in RNA

In eukaryotic cells, transcription cannot begin until...

...several transcription factors have bound to the promoter.

Spliceosomes are composed of...

...small RNAs and proteins

A particular triplet of bases in the template strand of DNA is 5'-AGT-3'. What would be the corresponding codon for the mRNA that is transcribed?

3'-UCA-5'

Use this model of a eukaryotic primary transcript to answer the following question. E = exon and I = intron 5'-UTR E1 I1 E2 I2 E3 I3 E4 UTR-3' If the primary transcript is processed and transported to the cytosol, which of the following molecules best represents the mRNA that will be produced?

5'-UTR E1 E2 E3 E4 UTR-3'

The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence ______.

CUG

The genetic code is essentially the same for all organisms. From this, one can logically assume which of the following statements to be true?

A gene from an organism can theoretically be expressed by any other organism.

After transcription begins, several steps must be completed before the fully processed mRNA is ready to be used as a template for protein synthesis on the ribosomes. Which three statements correctly describe the processing that takes place before a mature mRNA exits the nucleus?

A poly-A tail (50-250 adenine nucleotides) is added to the 3' end of the pre-mRNA. A cap consisting of a modified guanine nucleotide is added to the 5' end of the pre-mRNA. Noncoding sequences called introns are spliced out by molecular complexes called spliceosomes.

Transcription begins at a promoter. What is a promoter?

A site in DNA that recruits the RNA Polymerase

Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein?

A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.

Which of these is a tRNA?

B

Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?

Complementary

What determines which base is to be added to an RNA strand during transcription?

Base pairing between the DNA template strand and the RNA nucleotides. Transcription involved the formation of an RNA strand that is complementary to the DNA template strand.

In the diagram below, the two blue strands represent _______.

DNA

Which of these correctly illustrates the pairing of DNA and RNA nucleotides?

GTTACG CAAUGC

What is the name of the process shown in the diagram?

Initiation (of translation)

Which of the following processes correctly describes alternative RNA splicing?

It can allow the production of proteins of different sizes and functions from a single mRNA.

Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why?

It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-par substitution like this one.

What happens to RNA polymerase II after it has completed transcription of a gene?

It is free to bind to another promoter and begin transcription. The enzyme is free to transcribe other genes in the cell.

Where does RNA polymerase begin transcribing a gene into mRNA?

It starts after a certain nucleotide sequence called a promoter. In both eukaryotes and prokaryotes, RNA polymerase binds to the gene's promoter and begins transcription at a nucleotide known as the start point, although in eukaryotes the binding of RNA polymerase to the promoter requires transcription factors.

Which of the following statements about the function of RNA polymerase is correct?

It unwinds the double helix and adds nucleotides to a growing strand of RNA. RNA polymerase has several functions in transcription, including unwinding the DNA double helix and adding RNA nucleotides.

DNA does not store the information to synthesize which of the following?

Organelles

The initiator tRNA attaches at the ribosome's _______ site.

P

In the diagram below, the gray unit represents ________.

RNA polymerase RNA polymerase untwists a portion of the DNA double helix.

Which of the following statements best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.

What name is given to the process in which pre-mRNA is edited into mRNA?

RNA processing This process edits the RNA transcript that has been assembled along a DNA template.

Which component is directly involved in translation?

Ribosome

During transcription in eukaryotes, a type of RNA polymerase called RNA polymerase II moves along the template strand of the DNA in the 3'→5' direction. However, for any given gene, either strand of the double-stranded DNA may function as the template strand. For any given gene, what ultimately determines which DNA strand serves as the template strand?

The base sequence of the gene's promoter.

Two mRNAs (mRNA X and mRNA Y) are synthesized with the same exon sequences but poly-A tails of very different lengths. mRNA X is 7,500 bases long. mRNA Y is 6,900 bases long. The mRNA's are added to separate in vitro translation mixtures containing radioactive methionine and the reactions are allowed to proceed for 30 minutes. When the mixtures are analyzed which of the following outcomes will most likely occur?

The mRNA X mixture will contain more radioactive proteins than the mRNA Y mixture.

Which of the following is most likely to occur if a researcher removes the 5' cap and poly-A tail of an mRNA and inserts the mRNA molecule into a eukaryotic cell?

The molecule will be degraded by enzymes.

Which answer correctly compares the primary transcript in the nucleus of a eukaryotic cell with the functional mRNA?

The primary transcript is larger than the mRNA.

Which answer correctly compares the primary transcript in a prokaryotic cell with the functional mRNA?

The primary transcript is the same size as the mRNA.

Which of the following statements best described the promoter of a protein-coding gene?

The promoter is a non transcribed region of a gene. The promoter is the regulatory region of a protein-coding gene at which RNA polymerase must bind to initiate transcription - it is not transcribed into the RNA.

Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein? 5'-ATGCTAGCCTATCGTAAC-3'

The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift.

What is the process called that converts the genetic information stored in DNA to an RNA copy?

Transcription

What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?

Transcription

What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?

Translation

Suppose that a portion of double-stranded DNA in the middle of a large gene is being transcribed by an RNA polymerase. As the polymerase moves through the sequence of six bases shown in the diagram below, what is the corresponding sequence of bases in the RNA that is produced?

UGAGCC

Use the codon table to determine which mRNA triplets code for the amino acid cysteine, Cys.

UGC and UGU

What enzyme catalyzes the attachment of an amino acid to tRNA?

aminoacyl-tRNA synthetase

During RNA processing a(n) _______ is added to the 3' end of the RNA.

a long string of adenine nucleotides. A poly-A tail is added to the 3' end of the RNA.

Polypeptides are assembled from _________.

amino acids

Translation occurs in the ______.

cytoplasm

The RNA segments joined to one another by spliceosomes are _______.

exons Exons are expressed regions.

After an RNA molecule is transcribed from a eukaryotic gene, what are removed, and what are spliced together, to produce an mRNA molecule with a continuous coding sequence?

introns; exons Introns (intervening sequences) are removed and the exons (expressed sequences) are spliced together.

RNA processing converts the RNA transcript into ________.

mRNA

In the diagram below, the green unit represents _______.

the promoter

A codon consists of ______ bases and specifies which _______ will be inserted into the polypeptide chain.

three; amino acid

Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence?

wild-type5'-AUGCAUACAUUGGAGUGA- 3'mutant5'-AUGCAUACAUCUGGAGUGA-3'