What happens during rna splicing? rna polymerase adds nucleotides to an mrna strand. enzymes cut introns out of an mrna strand. a cap and tail are added to an mrna strand. transfer rna is removed from an mrna strand.

B (Enzymes cut introns out of an mRNA strand)

Explanation:

When an RNA transcript is first made in an eukaryotic cell, it is considered a pre-mRNA. Eukaryotes undergo processing of the pre-mRNA strand immediately after transcription. The genes of an eukaryote are split up into parts that are expressed as RNA products and parts that are not. The parts that contains the actual coding regions and are expressed are called EXONS while the parts removed from in between the exons and referred to as "junk sequences" are called INTRONS.

Introns and exons alternate with each other along the length of the gene. Introns are usually considered the non-coding regions because they don't seem to code for any protein, hence they are removed before the mRNA product is finally ready for translation. This post- transcriptional process is called RNA SPLICING. RNA SPLICING can be likened to the process of removing the chaff (introns) from the wheat (exons). It is the removal of introns and joining of exons in eukaryotic mRNA.

Splicing is carried out by SPLICEOSOMES ( a protein and RNA complex), which removes introns from the genes in mRNA. They locate the ends of the INTRONS, cut them away from the EXONS, and join the ends of adjacent exons together. Once the entire gene is devoid of introns, the process of RNA splicing is complete.

It is worthy to note that, not only do the introns not carry information to build a protein, they actually have to be removed in order for the mRNA to encode a protein with the right sequence. If the spliceosome fails to remove an intron, an mRNA with extra "junk" in it will be made, and a wrong protein will get produced during translation.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."