Name ___Datoya Brown___________ 

BIOL 430 Assignment 4

Due Thursday, October 25th

 

25 points

1.  You are interested in a gene called coeur , which you think may be involved in heart

development in Drosophila.a.  You perform in situ hybridization (ISH) on  Drosophila embryos, using a probe

that specifically recognizes the coeur mRNA, and observe staining specifically in

the embryonic heart. What can you conclude about coeur  mRNA expression based on this ISH experimental result? (3 points)

Based on the in situ hybridization (ISH) experimental results the conclusion is that the genecoeur mRNA is localized within the tissue ( Drosophila embryonic heart). This is stated because

obvious staining in the localized region provides insight as to the genes specific designation for 

activation in Drosophila species.

 b.  You then perform antibody staining using an antibody that specifically recognizes

the Coeur protein, and are surprised to find that you do not see staining anywhere

in the  Drosophila embryo, not even in the heart. What can you conclude aboutCoeur protein expression based on this antibody staining experimental result? (3 points)

Based on the antibody staining experimental results, the conclusion is that there is no visible

staining all over due to the technique used. Antibody staining is a method used to label a specific

 protein (in this case, the protein encoded by the gene coeur ) in a cell or tissue to determine

whether it is a present or absent.

c.  Propose at least one possible explanation for your observed experimental results.

(6 points)

A possible explanation for the observed experimental results is that in the Drosophila embryo the

coeur mRNA observed for expression in the heart has not been translated into the protein. In thecentral dogma the process is DNA → RNA → Protein at this point in the experiment has not

 processed thoroughly. In the translation stage, this is the actual synthesis of a protein, which

occurs under the direction of mRNA. In this particular  Drosophila embryo, mRNA has not

matured to express the protein needed for heart development.

 

 Name ___Datoya Brown___________ 

2.  What are the 5’ and 3’ UTR of an mRNA? How are they involved in regulating gene

expression? (8 points)

Gene expression is unusually regulated at the post-transcriptional level. UTRs are known to play

crucial roles in the post-transcriptional regulation of gene expression, including modulation of 

the transport of mRNAs out of the nucleus and of translation efficiency, subcellular localizationand stability. The 5’ UTR of an mRNA is any coding sequence just before the stop codon and the

3’ UTR is any coding sequence just after the start codon. 

3.  The nervy mRNA is expressed everywhere in the nervous system. However, thenervy 

mRNA contains two binding sites within its 3’UTR for a microRNA called miR-Brain.

The miR-Brain microRNA is expressed in the brain, but nowhere else within the nervous

system. Based on this information, predict the expression pattern of the Nervy proteinand explain your answer. (5 points)

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression by binding tothe 3’UTRs of target mRNAs, thereby preventing translation of that mRNA (and preventing

expression of that protein). Based on the information given, the prediction for the expression

 pattern of the Nervy protein is that it will be expressed everywhere in the nervous system.However, with the binding of the miR-Brain microRNA in the brain, only specific protein made

for the brain will be expressed, and all other nonspecific types will be inhibited, therefore not

allowed to be translated. The mRNA will still be accessible however, and will not be degraded.