Mastering Biology Chapter 14

A particular triplet of bases in the template strand of DNA is 5' AGT 3'. The corresponding codon for the mRNA transcribed is

3' UCA 5'.

Examine the table of codons in the figure. A possible sequence of nucleotides in the template strand of DNA that would code for the polypeptide sequence phe-leu-ile-val would be

3'-AAA-GAA-TAA-CAA-5'.

The direction of synthesis of an RNA transcript is _____.

5' —> 3'

In the diagram below, the two blue strands represent _____. The figure shows a blue molecule arranged in the form of a double chain. The gray unit on this figure represents an oval structure which contains unwound and unpaired chains of this molecule. Before and after this unit, the molecule is wound in the form of a double helix. A green unit represents a part of the double helix before the gray unit.

DNA

Polypeptides are assembled from _____.

amino acids

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

aminoacyl-tRNA synthetase

True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.

False

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

RNA processing

Where does translation take place?

Ribosome

Which of the following steps occurs last in the initiation phase of translation?

The large ribosomal subunit joins the complex.

Translation occurs in the _____.

cytoplasm

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

exons

DNA polymerase is very accurate and rarely makes a mistake in DNA replication. Occasionally, however, an error in replication, known as a point mutation, is introduced. There are two general categories of point mutations—frameshift mutations (also called base-pair insertions or base-pair deletions) and base substitution mutations (shown in the diagram). If a segment of DNA were replicated without any errors, the replicated strand would have the following sequence of nucleotides: 5' - ACTACGTGA - 3' Sort the following replicated DNA sequences by the type of point mutation each contains (frameshift, base substitution, or neither), as compared to the correct sequence shown above. Sort the items into the appropriate bins.

frameshift mutation: 5'-ACTTACGTGA-3' ; 5'-ACTCGTGA-3' base substitution mutation: 5'-ACTACGTGT-3' ; 5'-ACTAAGTGA-3' neither

Which of the following terms associated with transcription describe regions of nucleic acid? The figure shows a process of how the transcription of RNA polymerase moves along the DNA releasing a newly synthesized RNA molecule.

gene promoter terminator

What is the name of the process shown in the diagram? The figure shows a process which happens in the ribosome. During this process, a transport molecule which is localized in the central site of the ribosome binds to AUG sequence of the matrix molecule by its UAC site. This transport molecule also binds to Met molecule.

initiation (of translation)

Spliceosomes are composed of _____.

small RNAs and proteins

DNA is transcribed to messenger RNA (mRNA), and the mRNA is translated to proteins on the ribosomes. A sequence of three nucleotides on an mRNA molecule is called a codon. As you can see in the table, most codons specify a particular amino acid to be added to the growing protein chain. In addition, one codon (shown in blue) codes for the amino acid methionine and functions as a "start" signal. Three codons (shown in red) do not code for amino acids, but instead function as "stop" signals. Use the table to sort the following ten codons into one of the three bins, according to whether they code for a start codon, an in-sequence amino acid, or a stop codon.

start/methionine: AUG stop codon: UAA ; UAG ; UGA amino acid: AUC ; UGC ; ACU ; AAA ; CAC ; GCA

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

At which site do new aminoacyl tRNAs enter the ribosome during elongation?

A-site

Which of these is a tRNA? The figure shows a process of translation. Each letter marks a definite structure. Letter A marks the thread, to which the ribosome is attached. This thread is the base of the translation. Letter B marks the structure, which is bonded with Gly and is located inside the ribosome. Letter C marks the structure, in which the translation happens. Letter D marks the thread, which is formed by the translation. Letter E marks the structures, which are constituent elements of the forming thread.

B

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

CUG

Place the events in the transcription of a gene in their proper order from left (first event) to right (last event). Rank from first event to last event.

First Event -> Last Event (First) RNA polymerase binds promoter. RNA polymerase transcribes gene. RNA polymerase reaches terminator. (Last) RNA polymerase exits gene, RNA is released.

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

GTTACG CAAUGC

During translation, nucleotide base triplets (codons) in mRNA are read in sequence in the 5' → 3' direction along the mRNA. Amino acids are specified by the string of codons. What amino acid sequence does the following mRNA nucleotide sequence specify? 5′−AUGGCAAGAAAA−3′ Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens (e.g., Met-Ser-Thr-Lys-Gly).

Met-Ala-Arg-Lys

Before a molecule of mRNA can be translated into a protein on the ribosome, the mRNA must first be transcribed from a sequence of DNA. What amino acid sequence does the following DNA nucleotide sequence specify? 3′−TACAGAACGGTA−5′ Express the sequence of amino acids using the three-letter abbreviations, separated by hyphens (e.g., Met-Ser-His-Lys-Gly).

Met-Ser-Cys-His

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

P

Which of the following processes is an example of a post-translational modification?

Phosphorylation

In the diagram below, the gray unit represents _____. The figure shows a blue molecule arranged in the form of a double chain. The gray unit on this figure represents an oval structure which contains unwound and unpaired chains of this molecule. Before and after this unit, the molecule is wound in the form of a double helix. A green unit represents a part of the double helix before the gray unit.

RNA polymerase

What is meant by translocation?

The ribosome slides one codon down the mRNA.

Place the blue labels in their proper locations on this diagram showing the process of transcription. Then, use the pink labels to identify the corresponding RNA nucleotide that belongs in each pink target. Pink labels can be used once, more than once, or not at all. Drag the appropriate labels to their respective targets.

Top (Purple/Blue boxes): Nontemplate Strand ; RNA polymerase Middle (Purple/Blue boxes): Template Strand Middle (Pink boxes): A U G C Last (Purple/Blue boxes): RNA being produced

Generally speaking, which of the following mutations would most severely affect the protein coded for by a gene?

a frameshift deletion at the beginning of the gene

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

a long string of adenine nucleotides

When a base substitution mutation occurs, one nucleotide in a replicating DNA sequence is substituted for another, which results in the production of a mutant strand of DNA. The result of the mutation depends on how the substituted nucleotide base alters the string of amino acids coded by the mutant DNA. The three types of base substitution mutations are nonsense mutations, missense mutations, and silent mutations. Each type is defined by how it affects protein synthesis. Label the four mutated DNA segments shown below according to the type of point mutation each represents. Use the codon table above to determine how each mutation would affect the amino acid coding for each segment. Drag the labels to their appropriate locations to identify the type of point mutation shown.

a) silent mutation b) nonsense mutation c) missense mutation d) frameshift mutation

RNA processing converts the RNA transcript into _____.

mRNA

Which nucleic acid is translated to make a protein?

mRNA

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

modified guanine nucleotide

In the diagram below, the green unit represents _____. The figure shows a blue molecule arranged in the form of a double chain. The gray unit on this figure represents an oval structure which contains unwound and unpaired chains of this molecule. Before and after this unit, the molecule is wound in the form of a double helix. A green unit represents a part of the double helix before the gray unit.

the promoter

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

three ... amino acid