Which of the following processes is the best way to determine whether alternative splicing of a given gene occurs? Isolate mRNA from the given gene and compare the sequences. Gene expression is often assayed by measuring the level of mRNA produced from a gene.

Which of the following is the most likely phenotypes of a yeast mutant that contains histones that are resistant to acetylation? The mutant will show decreased levels of gene expression.

Histone acetylation alters chromatin structure. Acetylation of histones alters accessibility of chromatin and allows DNA binding proteins to interact with exposed sites to activate gene transcription and downstream cellular functions.

Early Studies in Bacteria Most bacterial RNA transcripts do not undergo splicing; these transcripts are said to be colinear, with DNA directly encoding them. In other words, there is a one-to-one correspondence of bases between the gene and the mRNA transcribed from the gene (excepting 5′ and 3′ noncoding regions).

Introns and exons are nucleotide sequences within a gene. Introns are removed by RNA splicing as RNA matures, meaning that they are not expressed in the final messenger RNA (mRNA) product, while exons go on to be covalently bonded to one another in order to create mature mRNA.

In most eukaryotic genes, coding regions (exons) are interrupted by noncoding regions (introns). During transcription, the entire gene is copied into a pre-mRNA, which includes exons and introns. During the process of RNA splicing, introns are removed and exons joined to form a contiguous coding sequence.

The pre-mRNA molecule thus goes through a modification process in the nucleus called splicing during which the noncoding introns are cut out and only the coding exons remain. Splicing produces a mature messenger RNA molecule that is then translated into a protein.

Introns, from this perspective, have a profound purpose. They serve as hot spots for recombination in the formation of new combinations of exons. In other words, they are in our genes because they have been used during evolution as a faster pathway to assemble new genes.

In particular, introns have a potential to serve as repositories of cis elements, participating in the regulation of transcription, and genome organization.

• Transcription initiation.
• Transcription termination.
• Genome organization.
• Nested genes.

Nuclear pre-mRNA introns (spliceosomal introns) are characterized by specific intron sequences located at the boundaries between introns and exons. These sequences are recognized by spliceosomal RNA molecules when the splicing reactions are initiated.

Exons are the regions of RNA that are used to produce amino acids and proteins. A gene on DNA contains more base pairs than necessary to produce the desired protein. These extra base pairs have to be removed so that the protein can function properly.

The exons are the sequences that will remain in the mature mRNA. Thus, the exons contain both protein-coding (translated) and non-coding (untranslated) sequences. Also note that the transcription of all mRNAs begins and ends with an exon and introns are located between exons.

Of course, UTRs ARE parts of exons. Usually of the first and the terminal exons for the 5′ and 3′ UTRs respectively, but not only.

​Exon. The parts of the gene sequence that are expressed in the protein are called exons, because they are expressed, while the parts of the gene sequence that are not expressed in the protein are called introns, because they come in between–or interfere with–the exons.

On average, there are 8.8 exons and 7.8 introns per gene. About 80% of the exons on each chromosome are < 200 bp in length.

five exons

Non-coding exons can contain some regulatory elements that modulate the protein expression, such as enhancers, silencer, or small non-coding RNA.

Non-coding DNA sequences are components of an organism’s DNA that do not encode protein sequences. Other functions of non-coding DNA include the transcriptional and translational regulation of protein-coding sequences, scaffold attachment regions, origins of DNA replication, centromeres and telomeres. …

The main difference between coding and noncoding DNA is that coding DNA represents the protein-coding genes, which encode for proteins, whereas noncoding DNA does not encode for proteins. Coding and noncoding DNA are two main types of DNA, which occur in the genome.

These are cut out of the mRNA and kept in the nucleus. Exons: Sections of mRNA containing the code to synthesize a protein. These are exported from the nucleus and proceed to the ribosome where they are used to synthesize the protein.

(Translation/Transcription) converts DNA into mRNA. (large ribosome subunitésmall ribosome subunit) Binds first with mRNA at the beginning of translation.

Eukaryotic DNA never leaves the nucleus; instead, it’s transcribed (copied) into RNA molecules, which may then travel out of the nucleus. In the cytosol, some RNAs associate with structures called ribosomes, where they direct synthesis of proteins.

RNA/DNA can leave the nucleus. mRNA is made during transcription/translation. mRNA is made in the cytoplasm/nucleus.