Biology Chapter 17 Test

Alternative RNA splicing..

-Can allow the production of proteins of dramatically different sizes from a single mRNA -Can allow the production of proteins of dramatically different amino acid sequences from a single mRNA

The function of the ribosome in polypeptide synthesis is to..

-Hold mRNA and tRNA together -Catalyze the addition of amino acids from tRNA to the growing polypeptide chain -Move along the mRNA and eject tRNAs during the translocation process.

The are 61 mRNA codons that specify an amino acid, but only 45 tRNAs. This is best explained by the fact that..

-Some tRNAs have anticodons that recognize two or more different codons. -The rules for base pairing between the third base of a codon and tRNA are flexible (wobble)

As a ribosome translocates along an mRNA molecule by one codon, what occurs?

-The tRNA that was in the A site moves into the P site -The tRNA that was in the P site moves to the E site and is released.

What is true of snRNPs?

-They are made up of both protein and RNA -They bind to splice sites at each end of the intron -They join together to form a large structure called a spliceosome

What components are present upon the completion of translation initiation?

-small ribosomal subunit - Large ribosomal subunit -Initiator tRNA

Which of the following is true about RNA? -snoRNA aids in processing pre-rRNA transcripts in the nucleolous -SRP RNA is an essential component of spliceosomes -It has functional groups that allows it to act as a catalyst (ribozyme)

-snoRNA aids in processing pre-rRNa transcripts in the nucleolus -It has functional groups that allow it to act as a catalyst (ribozyme)

An enzyme randomly assembles nucleotides into a polynucleotide polymer. You had the enzyme to a solution of adenosine triphosphate and guanosine triphosphate. How many different codons would be possible if the code involved two base sequences? What if it had three-base sequences?

1. 4 2. 8

Proper sequence of protein synthesis?

1. A small ribosomal subunit binds with mRNA 2. An aminoacyl-tRNA binds to the A site 3. A peptide bond forms between the new amino acid and a polypeptide chain. 4. tRNA translocates to the P site. 5. tRNA leaves the P site, and the P site remains vacant.

We know the one gene-one enzyme hypothesis is not entirely accurate because..

1. Many genes code for proteins that are not enzymes 2.A single gene codes for a single polypeptide chain, and many enzymes are made up of more than one polypeptide chain 3. Many genes code for RNA molecules that have no enzymatic activity

Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because..

1. RNA acts as an expendable copy of the genetic material, allowing the DNA to serve as a permanent, pristine repository of the genetic material. 2. Many mRNA molecules can be transcribed from a single gene, increasing the potential rate of gene expression.

If proteins were composed of only 12 different kinds of amino acids, what would be the smallest possible codon size in a genetic system with four different nucleotides?

2

An extraterrestrial life form is discovered. It has a genetic code much like that of organisms on Earth except that there are five different DNA bases instead of four and the base sequences are translated as doublets instead of triplets. How many different amino acids could be accommodated by this genetic code?

25

On what end of the growing transcript does RNA add nucleotides?

3'

What direction does RNA polymerase move along the template strand of DNA?

3' to 5'

A particular eukaryotic protein is 300 amino acids long. What could be the maximum number of nucleotides in the DNA that codes for the amino acids in this protein?

900

Which point mutation would be most likely to have a catastrophic effect on the functioning of a protein?

A base deletion near the start of a gene

Which of the DNA mutation is the most likely to be damaging to the protein it specifies?

A base-pair deletion

When translating secretory or membrane proteins, ribosomes are directed to the ER membrane by..

A signal-recognition particle that brings ribosomes to a receptor protein in the ER membrane.

During translation, chain elongation continues until what happens?

A stop codon is encountered

What does not occur during the termination phase of translation?

A tRNA with the next amino acid enters the P site.

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

AAA

The nitrogenous base adenine is found in all members of which group?

ATP, RNA, and DNA

What is a ribozyme?

An enzyme made up of RNA

What is the first event in translation in eukaryotes?

Base pairing of activated methionine-tRNA to AUG of the messenger RNA.

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

Bonding of the anticodon to the codon Attachment of amino acids to tRNAs

What are ribosomes composed of?

Both rRNA and protein

What is not DIRECTLY involved in translation..

DNA

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

DNA was the first genetic material

When does translation begin in prokaryotic cells?

During transcription

A frameshift mutation could result from..

Either an insertion or a deletion of a base

Once transcribed, eukaryotic mRNA typically undergoes substantial alteration that includes..

Excision of introns

A mutation in what part of a gene is likely to be most damaging to a cell?

Exon

What are the coding segments of a stretch of eukaryotic DNA called?

Exons

What molecules are transcribed from DNA?

Exons and rRNA

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.

What are polyribosomes?

Groups of ribosomes reading a single mRNA simultaneously.

What type of bonding is responsible for maintaining the shape of the tRNA molecule?

Hydrogen bonding between base pairs

What is not found in prokaryotic mRNA?

Introns

What is the effect of a nonsense mutation in a gene?

It introduces a stop codon in the mRNA

Which of the following is not directly involved in the process of translation?: -Ligase -tRNA -rRNA -mRNA -aminoacyl-tRNA synthetase

Ligase

A transcription unit that is 8000 nucleotides long may use 1200 nucleotides to make a protein consisting of 400 amino acids. This is best explained by the fact that..

Many noncoding nuleotides are present in mRNA

A codon..

May code for the same amino acid as another codon.

What is a similarity between RNA and DNA?

Nucleotides consisting of a phosphate, sugar, and nitrogenous base.

Sickle-cell disease is probably the result of which kind of mutation?

Point

Of the following types of mutations (point, missense, base-pair substitution, nonsense, frameshift) which is likely to be the MOST COMMON

Point mutation

If the triplet CCC codes for the amino acid proline in bacteria, then in plants CCC should code for..

Proline

A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of 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 specificed by the codon UUU.

During splicing, which molecule component of the splicesome catalyzes the excision reaction?

RNA

What is true for both prokaryotic and eukaryotic gene expression?

RNA polymerase binds to the promoter region to begin transcription

RNA Polymerase and DNA Polymerase differ in that..

RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis.

What best describes the termination of transcription in prokaryotes?

RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript.

Which of the following is least related to the other items? -Exons -Introns -RNA splicing -Signal-recognition particles (SRPs) -mRNA

Signal-recognition particles (SRPs)

Which of the following is not related to ribosomal activity? -A site -Spliceosome -Codon Recognition -Peptide bond formation -P Site

Spliceosome

What helps to stabilize mRNA by inhibiting its degradation?

The 5' cap and Poly-A Tail

Where is eukaryotic ribosomal RNA transcribed?

The nucleolous

Introns are significant to biological evolution because..

Their presence allows exons to be moved around more easily, creating proteins with new combination of functional domains.

What is one function of a signal peptide?

To translocate polypeptides across the ER membrane

What of the following are least related: Translation TATA box Transcription Template strand RNA Polymerase II

Translation

What statements are true about protein synthesis in prokaryotes?

Translation can begin while transcription is still in progress.

Part of an mRNA molecule with the following sequence is being read by a ribosome: 5' CCG-ACG 3' Two of the anticodons are available. (flip the letters THEN search for the amino acid)

proline-threonine

What is the most abundant type of RNA?

rRNA

What is not a part of the eukaryotic transcription initiation complex?

snRNP

Which of the following is LEAST related to the other items?: 1.snRNP 2. Triplet Code 3. Wobble 4.tRNA 5. Anticodon

snRNP

What is an anticodon part of?

tRNA