Transcription & Gene Expression (DP IB Biology: HL)

Which of the following statements describes the promoter?

In humans, during periods of hypoxia (low oxygen in tissues) the transcription factor HIF (Hypoxia-Inducible Factor) binds to the Hypoxia Response Element (HRE) sequence and increases transcription of the EPO gene. This stimulates the production of red blood cells. The diagram shows the EPO gene and regulatory elements.                                                                                  

Which kind of regulatory elements are HIF and HRE?

Which of the following occur in the bacterium Escherichia coli if no lactose is present?

Identical twins have the same DNA (genotype) but often display many observable physical differences (phenotype). Studies on twins have shown that one twin can be more susceptible to diseases like cancer or diabetes.

Which of the following statements best explains these differences between identical twins?

The diagram below shows a nucleosome where the histone tails have had an acetyl group added.

Which statement best describes the effect of acetylation of histone tails?

The simplified diagram below shows a section of DNA where a methyl (-CH₃) group has been added to a cytosine base.   

Which of the following best describes the outcome of direct methylation of DNA?

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?

Which of the following statements about DNA methylation are correct?

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?

Which of the following applies to both mutations and epigenetics?

1. It may affect the visible characteristics of an organism
2. The DNA base sequence can change and impact the expression of genes
3. Environmental factors may play an important role in the development of changes
4. Modifications may be passed on to the next generation at a cellular level
5. The amino acid tails of histones are modified by methylation, acetylation and phosphorylation

Female embryos contain two copies of the X chromosome, even though they initially do not need both copies to be active. In order to avoid producing double the amount of polypeptides required, the paternal X chromosome is inactivated during the first few divisions after fertilisation. This is done by the methylation of lysine on different histones.

Which of the following provides the most accurate explanation of how this would inactivate the paternal X chromosome?

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.