Question

Describe the central dogma of cell biology by explaining each step as well as where each step takes place in the cell. Make sure to include the terms: transcription, mRNA, splicesome, introns, exons, translation, ribosomes, primary transcript, nucleus, cytoplasm, and endoplasmic reticulum.

Answer 1

The central dogma of biology describes just that. It provides the basic framework for how genetic information flows from a DNA sequence to a protein produced inside cells. This process of genetic information flowing from DNA to RNA to protein is called gene expression.

Thus DNA replicates to form DNA and transcription of the template strand of DNA forms various types of RNA such as t RNA, r RNA, m RNA etc. Transcription and replication both occur in the nucleus and as soon as the m RNA is formed it moves inside the cytoplasm through the nuclear pore into the cytoplasm or ribosomes where translation or protein synthesis takes place. Initially, the m RNA formed is called pre m RNA transcript. This is changed to the final m RNA transcript through post-transcriptional modification. Post-transcriptional modifications of pre-mRNA, such as capping, splicing, and polyadenylation, take place in the nucleus. After these modifications have been completed, the mature mRNA molecules have to be translocated into the cytoplasm, where protein synthesis occurs. In this process introns or the non-coding sequences are also removed and exons are lined up together to assist in translation.

A spliceosome is a large and complex molecular machine found primarily within the nucleus of eukaryotic cells. The spliceosome is assembled from small nuclear RNAs (snRNA) and approximately 80 proteins. The spliceosome removes introns from a transcribed pre-mRNA, a type of primary transcript. Ribosomes present on the surface of endoplasmic reticulum are delivering proteins directly inside the lumen of ER. Proteins meant for use outside the cell (products like enzymes and hormones), are kept temporarily inside secretory vesicles before being secreted