Explanation:
The Exon Junction Complex (EJC) is a eukaryotic molecular machine that interacts with spliced mRNA upstream of exon-exon junctions, providing a binding platform for other trans-acting proteins that determine the fate of the mRNA. The spliceosome deposits the ~335kD EJC in a non-sequence specific manner 20-24 nucleotides upstream of an exon-junction. Functionally, the EJC aids in nuclear export of spliced mRNAs, assists in nonsense-mediated decay of incorrectly spliced mRNAs containing premature stop codons, and enhances translation efficiency.
Pre-mRNA bound by a spliceosome is usually not exported from the nucleus, so as to make sure that only fully-processed mRNA travels to the cytoplasm to be translated. A protein called the mRNP exporter binds to the EJC, both through RNA interactions and interactions with the EJC-associated protein REF (RNA export factor) to help pre-mRNA exit the nuclear pore complex.
Interestingly, the efficiency of unspliced mRNA export is dependent on the length; longer mRNAs are exported more efficiently than shorter mRNAs. In spliced mRNAs, however, once the 5' exon is long enough to bind the EJC, the length of the spliced mRNA does not affect the export efficiency.
There are a certain number of EJCs in a cell, and they must be recycled in order to continue tagging mature mRNAs. Once in the cytoplasm, the ribosome-associated regulator protein (PYM) acts as a dissociation factor.
Answer:
B) They are not in the same species.
Explanation:
Cat and dog both are domestic animals but the can not interbreed to produce fertile offspring. Specie is define as those animal which can interbreed to produce fertile offspring so the cat and dog can not interbreed as they belong to two different species. Both species have different <u>chromosome number</u> that's why the can not interbreed. In order to interbreed both the organisms must belong to one specie. E.g As both tiger and lion live in one environment and the interbreed and produce tiglion but it is infertile and can not breed to produce offspring.
Answer:
Genetic variation is caused by:
mutation
random mating between organisms
random fertilization
crossing over (or recombination) between
chromatids of homologous chromosomes during
meiosis
<span>Answer:
For ectotherms, on the other hand, body temperature mainly depends on external heat sources. That is, ectotherm body temperature rises and falls along with the temperature of the surrounding environment. Although ectotherms do generate some metabolic heat—like all living things—ectotherms can't increase this heat production to maintain a specific internal temperature.</span>
