Chapter 17 From Gene to Protein

What is the proper order of the following events in the expression of a eukaryotic gene? 1. translation 2. RNA processing 3. transcription 4. modification of protein

3, 2, 1, 4 transcription, RNA processing, translation, modification of protein

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.

How many nucleotides are needed to code for a protein with 450 amino acids?

At least 1,350

Who formulated the one gene-one enzyme hypothesis?

Beadle and Tatum

Which of the following is a post-translational modification of a polypeptide?

Cleavage of a polypeptide into two or more chains

What is a key difference in gene expression between eukaryotic and prokaryotic cells?

In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing.

*What is the function of the release factor during translation in eukaryotes?*

It binds to the stop codon in the A site in place of a tRNA.

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-pair substitution like this one.

*Which of the following statements correctly describes a ribozyme?*

It is an RNA with catalytic activity

What is the function of RNA polymerase?

It unwinds the double helix and adds nucleotides to a growing strand of RNA

*Once researchers identified DNA as the molecule responsible for transmitting heritable traits, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. Which of the following statements correctly describes the mechanism of information transfer in eukaryotes that accomplishes this task?*

Messenger RNA is transcribed from a single gene and transfers information from the DNA in the nucleus to the cytoplasm, where protein synthesis takes place.

*The genetic code is redundant. What is meant by this statement?*

More than one codon can specify the addition of the same amino acid

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?

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

One strand of a DNA molecule has the following sequence: 3-AGTACAAACTATCCACCGTC-5. In order for transcription to occur in that strand, there would have to be a specific recognition sequence, called a(n) __________, to the left of the DNA sequence indicated.

Promoter

Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of __________.

RNA

*Which of the following processes occurs during transcription?*

RNA is synthesized

Which of the following catalyzes the linkage between ribonucleotides to form RNA during gene expression?

RNA polymerase

*Which one of the following statements about RNA processing is correct?*

Ribozymes may function in RNA splicing

Which of the following best describes the arrangement of genetic information in a DNA molecule?

The three-nucleotide words of a gene are arranged in a nonoverlapping series on the DNA template strand.

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.

__________ is the synthesis of RNA using information in the DNA.

Transcription

__________ is the synthesis of a polypeptide using information in the mRNA.

Translation

When RNA is being made, the RNA base _________ always pairs with the base __________ in DNA.

U; A

*Which of the following statements is the most current description of a gene?*

a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

Because the bacterial cell's DNA is not surrounded by a nuclear envelope, __________ occur(s).

coupled transcription and translation

The function of tRNA during protein synthesis is to __________.

deliver amino acids to their proper site during protein synthesis

Stop codons are unique because they __________.

do not code for amino acids that allow a releasing factor to bind to the A site of the ribosome

The TATA box is a __________ that allows for the binding of __________ and __________.

eukaryotic promoter; transcription factors; RNA polymerase II

Insertions and deletions are called __________ mutations.

frameshift

Polysomes may be defined as __________.

groups of ribosomes

The bonds that hold tRNA molecules in the correct three-dimensional shape are __________.

hydrogen bonds

*Which of the following molecular structures contain codons?*

mRNA

*Which of the following molecules are required for the process of translation?*

mRNA, tRNA, and rRNA

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

missense

The sickle-cell β-globin mutation is an example of a __________.

missense mutation

A ___________ mutation causes an early Stop codon to occur.

nonsense

The type of point mutation that results in a premature stop codon is called a _________ mutation.

nonsense

By bombarding the fungus Neurospora crassa with X-rays, Beadle and Tatum were able to study __________ and characterize enzymes in a __________.

nutritional mutants; biochemical pathway

The structures called snRNPs are __________.

part of a spliceosome

RNA molecules that function as enzymes are called __________.

ribozymes

In eukaryotic cells, a __________ by a __________ targets a growing peptide to the endoplasmic reticulum.

signal peptide; signal-recognition particle

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

silent

An exception to the one gene-one enzyme hypothesis is __________.

that not all genes code for enzymes; some genes code for structural proteins such as keratin

Eukaryotic processing of the primary transcript includes __________.

the addition of a 5ꞌ cap, a 3ꞌ poly-A tail, and the splicing out of introns

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

Bacteria can transcribe and translate human genes to produce functional human proteins because __________.

the genetic code is nearly universal

Gene expression is __________.

the process by which DNA directs the synthesis of proteins

*Which of the following processes is the first event to take place in translation in eukaryotes?*

the small subunit of the ribosome recognizes and attaches to the 5 cap of mRNA

The "triplet code" refers to the fact that _________.

three nucleotides code for a single amino acid

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

wild-type 5'-AUGCAUACAUUGGAGUGA-3' mutant 5'-AUGCAUACAUCUGGAGUGA-3'