Biology chapter 14

Put the following events of elongation in prokaryotic translation in chronological order. 1. Binding of mRNA with small ribosomal subunit 2. Recognition of initiation codon 3. Complementary base pairing between initiator codon and anticodon of initiator tRNA 4. Base pairing of the mRNA codon following the initiator codon with its complementary tRNA 5. Attachment of the large subunit

1, 2, 3, 5, 4

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'

Rank the following one-base point mutations (from most likely to least likely) with respect to their likelihood of affecting the structure of the corresponding polypeptide. 1. insertion mutation deep within an intron 2. substitution mutation at the third position of an exonic codon 3. substitution mutation at the second position of an exonic codon 4. deletion mutation within the first exon of the gene

4, 3, 2, 1

Which of the following does not occur in prokaryotic gene expression, but does occur in eukaryotic gene expression?

A cap is added to the 5' end of the mRNA.

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

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

Which of the following contradicts the one-gene, one-enzyme hypothesis?

A single antibody gene can code for different related proteins, depending on the splicing that takes place post-transcriptionally.

During elongation, which site in the ribosome represents the location where a codon is being read?

A site

How does termination of translation take place?

A stop codon is reached.

A particular triplet of bases in the coding sequence of DNA is AAA. The anticodon on the tRNA that binds the mRNA codon is _____.

AAA

Which one of the following, if missing, would usually prevent translation from starting?

AUG codon

Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?

Codons are a nearly universal language among all organisms.

Which of the following best describes the significance of the TATA box in eukaryotic promoters?

It is the recognition site for a specific transcription factor.

What must occur before a newly made polypeptide is secreted from a cell?

Its signal sequence must target it to the ER, after which it goes to the Golgi.

Once researchers identified DNA as the unit of inheritance, they asked how information was transferred from the DNA in the nucleus to the site of protein synthesis in the cytoplasm. What is the mechanism of information transfer in eukarotes?

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.

What does it mean when we say the genetic code is redundant?

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

How might a single base substitution in the sequence of a gene affect the amino acid sequence of a protein encoded by the gene, and why?

Only a single amino acid could change, because the reading frame is unaffected.

In the process of transcription, _____.

RNA is synthesized

In eukaryotes there are several different types of RNA polymerase. Which type is involved in transcription of mRNA for a globin protein?

RNA polymerase II

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.

Which one of the following statements about RNA processing is true?

Ribozymes may function in RNA splicing.

In an experimental situation, a student researcher inserts an mRNA molecule into a eukaryotic cell after she has removed its cap and poly-A tail. Which of the following would you expect her to find?

The molecule is digested by enzymes because it is not protected at the end.

Which of the following statements is true about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress.

Of the following, which is the most current description of a gene?

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

Which of the following DNA mutations is most likely to damage the protein it specifies?

a base-pair deletion

A single base substitution mutation is least likely to be deleterious when the base change results in _____.

a codon that specifies the same amino acid as the original codon

Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?

a deletion of two nucleotides

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in _____.

a polypeptide missing an amino acid

Post-translational modifications of proteins may include the _____.

addition of carbohydrates to form a glycoprotein

A ribozyme is _____.

an RNA with catalytic activity

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _____.

binding of the anticodon to the codon and the attachment of amino acids to tRNAs

The release factor (RF) _____.

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

Alternative RNA splicing _____.

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

4-9

chart

Which of the following occurs in prokaryotes but not in eukaryotes?

concurrent transcription and translation

An original section of DNA has the base sequence AGCGTTACCGT. A mutation in this DNA strand results in the base sequence AGGCGTTACCGT. This change represents _____.

frameshift mutation

Garrod hypothesized that "inborn errors of metabolism" such as alkaptonuria occur because _____.

genes dictate the production of specific enzymes, and affected individuals have genetic defects that cause them to lack certain enzymes

A signal peptide _____.

helps target a protein to the ER

A nonsense mutation in a gene _____.

introduces a premature stop codon into the mRNA

A primary transcript in the nucleus of a eukaryotic cell is _____ the functional mRNA, while a primary transcript in a prokaryotic cell is _____ the functional mRNA.

larger than; the same size as

According to the central dogma, what molecule should go in the blank?

mRNA

Codons are part of the molecular structure of _____.

mRNA

Translation requires _____.

mRNA, tRNA, and rRNA

28

model

38-42

pictures

A mutant bacterial cell has a defective aminoacyl-tRNA synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of the normal phenylalanine. The consequence of this for the cell will be that _____.

proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU

Transcription in eukaryotes requires which of the following in addition to RNA polymerase?

several transcription factors

There are sixty-one mRNA codons that specify an amino acid, but only forty-five tRNAs. This is best explained by the fact that _____.

the rules for base pairing between the third base of a codon and tRNA are flexible

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

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

Which of the following is directly related to a single amino acid?

the three-base sequence of mRNA

In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?

the various domains of the polypeptide product

Once a peptide has been formed between the amino acid attached to the tRNA in the P site and the amino acid associated with the tRNA in the A site, what occurs next?

translocation