Gene Regulation!

What is occurring in this diagram?

• This is an mRNA which is being replicated. Two exonucleases can now chop the ends of the sequences and degrade the mRNA strands.

• This is mRNA degradation. Endonuclease enzyme cuts the mRNA into two fragments. Two exonucleases can now hydrolyse at 3’ end or 5’ end.

• After the mRNA strand is cleaved into two different fragments by endonuclease, two enzymes attach to the ends, ligating the enzymes. This is so that they can attach to the surface of the cell which inactivates them.

• The mRNA eventually degrades naturally into two pieces. The sequences now become nonfunctional as they are disconnected

What is occurring in this diagram?

• Once the original mRNA sequence has been shortened in length by cutting enzymes, it can extend through the cell membrane, leaving the cytoplasm and rendering the sequence nonfunctional.

• Firstly, an enzyme removes the 3’ poly-A tail (deadenylation). Then, an enzyme removes the 5’ cap (decapping). The sequence is now nonfunctional without these important end parts on the sequence.

• Firstly, an enzyme removes the 3’ poly-A tail (deadenylation). Then, an enzyme removes the 5’ cap (decapping). Now, both the 3’ and 5’ ends are exposed, allowing exonucleases to cut the strand into small pieces.

• An enzyme starts chopping 5’ end, before another enzyme starts chopping at the 3’ end of the strand. Eventually, these enzymes will stop when near each other, at which point the sequence is nonfunctional.

Cell Regulation relies on many factors -intrinsic or extrinsic. Which of the following are cell extrinsic regulation factors? Environmental cues mean from outside of the cell.

Select all that Apply:

• Modified DNA

• Small Molecules and Temperature

• Secreted Proteins and Oxygen

• Modified Chromatin

• Cell cues from other cells in organism or organisms environment

Which of the following are types of gene expression?

• Intrinsic gene expression

• External specificity

• Repressed expression

• Temporal specificity

• Induced expression

mRNA degradation from exonucleases and endonucleases causes the sequence to become translationally inactive.

• True

• False

How do the transcription factors (TATA binding proteins and TATA associated factors), binding to the TATA box in the promoter sequence allow gene expression?

• The conformation of this allows RNA polymerase II to bind, which can then move downstream to express gene of interest.

• Transcription factors binding to the promoter, provides a bridge that attaches to the rest of sequence. This enables RNA polymerase to move downstream and express gene of interest.

• Transcription factors provide a force to allow RNA polymerase, enabling it to motion towards gene so that it can be expressed.

• When transcription factors bind to the promoter sequence, repressor proteins are blocked from accessing the sequence. This stops repressors from silencing gene expression and allows expression of the gene.

How does a repressor binding to a silencer repressor gene express? This diagram can be used to aid your answer

• A silencer will recruit other enzymes and proteins. These methylate the gene of interest, covering it which prevents RNA polymerase from accessing them, and stops gene expression.

• A silencer causes RNA polymerase to dissociate from template, preventing it from moving downstream to gene of interest and repressing gene expression.

• A repressor binding to a silencer inactivates RNA polymerase, preventing gene expression from occurring.

• A repressor binding to a silencer, means that the repressor is in the vicinity of RNA polymerase II, preventing it moving to gene of interest, silencing gene expression.

What are the three different molecules in the promoter sequence, in order from the most upstream to downstream?

• TATA box, GC box and CAAT box.

• TATA box, MOOUSE box, and GC box.

• TATA box, CAAT box and GC box.

• CAAT box, TATA box, and GC box.

Trans-acting elements, also called transcription factors bind to gene promoter and enhancers to help drive transcription. Different types of protein bind to each cis-acting elements. Which of the following are the two correct answers?

• Silencers bind to RNA Polymerase

• Activators and Repressors bind to enhancers

• Basal Factors Bind to Promoters

• Oligo dTs bind to the Poly-A Tail on a single stranded mRNA template

Gene regulation can occur at a structural level. Eukaryotic DNA is packaged into chromatin which begins with the organisation of DNA into nucleosomes. If chromatin are actively open, and contain unmethylated cytosine with deacetylated histone tails, which outcome would result regarding gene expression?

• Translation of the gene will turn on and gene expression will occur due to promoter sequence being exposed.

• Translation of the gene will not occur and gene expression will not occur.