The correct answer is A-T rich DNA. DAPI is a common fluorescent dye used in immunohistochemistry to stain DNA to indicate the localization of the nucleus within a cell, relative to other structures and regions. When bound to DNA, it absorbs ultraviolet light (358nm) and emits blue light (461nm). 

When performing immunohistochemistry, antibodies are often utilized to detect proteins of interest within the cell. However, in order for antibodies to enter fixed cells, there must be holes (pores) artificially made in the cell membrane. 

Homologous recombination and Crispr-Cas9 create stable gene knockouts whereas shRNA and morpholino interference transiently knockdown a gene of interest. The GAL4-UAS system acutally is used to overexpress a gene of interest. By using a cell type specifc promoter, researchers are able to overexpress a specific protein in a desired cell type in a whole organism. 

The only result that would be very unlikely is the one in which the null has a larger head size than the hypomorph. All of the other cases could be true since the nature of a hypomorph is often hard to ascertain, but given that more protein = bigger head, a true genetic null would have the least amount of protein (i.e. no protein) and represents the absolute smallest a head can get. 

RNA interference (RNAi) takes use of the cell's internal machinery to locate a target mRNA transcript and stall its translation, or degrade it completely. It is a very powerful tool for silencing genes. Small RNA transcripts bind to mRNA, either silencing translation or labeling the mRNA for destruction.

qPCR is a technique used to measure gene expression. FPLC is used to purify proteins. X-ray crystallography is used to elucidate protein structures.

RNAi is a process that utilizes small molecules of RNA (miRNA or siRNA) to target specific molecules of mRNA, repressing their translation or cleaving them into non-functional units. This essentially prevents the expression of a particular protein by neutralizing its mRNA transcript. Ribosomes may fail to bond with the region of double-stranded RNA, created from the mRNA and RNAi dimer, or it may attract nucleases.

RNAi is not involved in globally halting translation and is not used to target tRNA or ribosomes.

Double-stranded RNA molecules are dicer's substrate, and their presence initiates the RNAi process. The other molecules listed are not cleaved by dicer proteins.

The correct answer is argonaute. Argonaute is part of the RISC and binds small non-coding RNAs. These RNAs guide argonaute to their specific targets via complementary base pairing, leading to mRNA cleavage and subsequent inhibition of translation. Dicer generates double-stranded RNA fragments, and endonucleases and RNA helicases are not specific to RNAi. 

RNAi molecules are double stranded RNAs. Their sequences are complementary to the sequence of the mRNA in which they are designed to destruct, thus allowing them to bind and trigger the degradation process. 

Since we can assume the RNAi correctly targets and degrades the proper mRNA, we can expect that the levels of Enzyme A will be decreased in the fly expressing the RNAi against Enzyme A. Because Gene A's mRNA will be degraded, little or no protein will be produced from Gene A, and thus the fluorescent antibody against Enzyme A will have nothing to bind to, which will result in less fluorescence in the fly expressing the RNAi versus the fly with undisturbed translation of the mRNA.