Protein Synthesis (HL IB Biology)

A polypeptide has the following amino acid sequence:

alanine - alanine - valine - lysine - valine - serine

The table below gives the base sequences for the DNA triplets of each amino acid.

A mutation in the DNA coding for this polypeptide chain caused the tenth nucleotide to change from an A to a T.

Which of the following would represent the amino acid sequence in the polypeptide after the mutation occurred?

Which of the following processes involve both DNA and RNA?

I. Replication

II. Transcription

III. Translation

IV. Protein synthesis

A short section of mRNA that was produced after transcription occurred has the following base sequence:

AAACUUCUCAUAGAACGG

The following table shows the base sequence for codons and the corresponding amino acids that they code for.

Which of the following would represent the correct amino acid sequence coded for by this section of mRNA?

A polypeptide has the following amino acid sequence:

histidine - glutamine - lysine - alanine - valine - histidine - valine

The table below gives the tRNA anticodons for each amino acid.

A mutation causes the 18^th base in the DNA sequence to be deleted. 

Which of the following would represent the amino acid sequence after this deletion?

The reaction of bacteria to DNA damage is called the SOS response. During this response, the cell cycle stops and a DNA damage repair system is induced. Two main proteins are involved, namely LexA and RecA. In normal cells, the LexA protein is bound to a section of prokaryotic DNA called the SOS box, which codes for various genes involved with DNA repair. In cells with DNA damage, RecA will bind to and cleave the LexA protein.

Which of the following correctly identifies each of the components of the SOS response?

The muscle protein titin is an important component of cardiac muscle tissue. Several forms of titin exist, even though it is coded for by the same gene. During the development of the foetal heart, titin exists in the form of long, springy protein strands, while in the adult heart titin is much shorter.

Which of the following provides the most plausible explanation for the occurrence of the different forms of titin?

Which of the following provides a reason why prokaryotic mRNA does not require post-transcriptional modification?

1. Prokaryotic DNA is a circular, double-stranded molecule, therefore mRNA molecules are less complex than in eukaryotes.
2. A lack of a nuclear membrane means that transcription and translation can be coupled together.
3. Prokaryotic DNA lacks introns, which means that no splicing needs to occur.
4. Prokaryotes have smaller, 70S ribosomes.
5. RNA polymerase in prokaryotes will transcribe a single strand of mRNA.

Which of the following enables tRNA activating enzymes to link an amino acid to a tRNA molecule?

Which of the following applies to both free and bound ribosomes?

1. They produce polypeptides that are destined to be used for processes occurring in the cytosol
2. Translation is interrupted and then re-initiated once movement of the ribosome is complete
3. They are found in all eukaryotic cells and may be either 70S or 80S
4. They facilitate the binding of mRNA and tRNA and catalyse the formation of peptide bonds
5. They have four binding sites to allow the molecules involved with translation to attach to its subunits

Leucine is an essential amino acid (EAA) that plays an important role in initiating the process of translation. Scientists investigated the effect of leucine on the process of protein synthesis and protein breakdown in muscles. Participants of the study were divided into three equal groups. Each group were given the same diet that was supplemented with different amounts of leucine (High, low and no added leucine) and the rate of protein synthesis and protein breakdown were monitored over time.

The diagram below shows the results of this study.

Which of the following provides the most plausible conclusion that can be drawn from the data?

The following steps describes the events taking place during the elongation of a polypeptide in no particular order.

1. Free tRNA molecules bind to their corresponding amino acids due to their specific anticodon and transport it to the ribosome 
2. A tRNA with a complementary anticodon binds to the "A" site bringing its specific amino acid along
3. The initiator tRNA moves from the "P" to the "E" site on the ribosome where it initiates translation
4. The amino acid carried by the tRNA at the "P" site is linked to the polypeptide chain by a peptide bond
5. tRNA carrying the peptide chain moves from the "A" site to the "P" site as the ribosome moves in the 5' → 3' direction along the mRNA molecule

Which of these steps contain incorrect information?

A piece of DNA was analysed to find the number of nucleotide bases in each of the polynucleotide strands.  Some of the results are shown below.

What is the maximum number of amino acids that could be coded for by this DNA?

What is the correct sequence for the processes involved in the formation of a protein?

Which of the following statements about transcription are true? 

1. DNA remains in the nucleus because it is too large to fit through the pores in the nuclear envelope.
2. Transcription makes a copy of the sense strand of DNA.
3. Transcription converts a sequence of nucleotides into a sequence of amino acids.
4. RNA polymerase forms covalent bonds between the RNA nucleotides.

What terminates the formation of a polypeptide chain during protein synthesis in cells?

Which row of the table contains three correct statements about DNA replication, transcription and translation?

The majority of the eukaryotic genome contains non-coding regions of DNA.

 Which of the following are functions of non-coding DNA?

Which of the following statements describes the promoter?

Which of the following statements about transcription are correct?

It is estimated that the human genome contains between 20 000 and 25 000 genes. However, the proteome is estimated to contain up to 400 000 proteins. This large difference in numbers is due to alternative splicing.

Which of the following best describes alternative splicing in eukaryotes?

Which of the following accurately describes the sequence of steps that happen following production of a pre-mRNA in eukaryotes?

What is the correct sequence of events during the initiation stage of translation in eukaryotes?

1. Small subunit of the ribosome binds to the 5’ end of mRNA
2. Large ribosomal subunit binds to form the ribosome complex
3. The ribosomal subunit moves along the mRNA until it locates a start codon
4. An initiator tRNA binds
5. Elongation of the polypeptide chain can begin                                                                                                                                  

   	first	→	→	→	last
   A	I	II	III	V	IV
   B	II	I	IV	III	V
   C	I	II	III	IV	V
   D	I	IV	III	II	V

Which of the following is not a function of tRNA?

During the elongation stage of translation the ribosome ‘translocates’ along the mRNA moving in a 5’ → 3’ direction.

What is the immediate effect of this directional movement?

In eukaryotic cells, ribosomes can be either free or bound.

Which of the following proteins would most likely be synthesised by bound ribosomes?

The diagram below represents an electron micrograph of eukaryotic polysomes.

What is the main advantage that polysomes give to a eukaryotic cell?