Central Dogma of Biology - Genetics

The central dogma of biology is best described by DNA is transcribed to RNA, which is translated to protein. The genetic material (DNA) is transcribed into mRNA (RNA) which is than translated into proteins. The central dogma is an important principle in molecular biology, and it helps explain why DNA plays such an important role in genetic expression.

Transcription begins when RNA polymerase binds to promoter DNA sequences on a gene. This leads to the production of a RNA chain, complimentary to the original (template) DNA strand.

RNA is transcribed 5' to 3' ALWAYS, meaning that the template DNA strand is read from the 3' to 5' direction.

Eukaryotes are more complex cells than prokaryotes and have 3 different polymerases for the different RNA classes, while prokaryotes only have one RNA polymerase that handles RNA transcription for the whole cell.

The 5’ UTR region is known as the leader sequence and runs upstream from the coding sequence. The 3’ UTR region is the trailer sequence and runs downstream to the coding sequence. The start codon runs after the 5’ UTR region and the stop codon is seen prior to the 3’ UTR region.

mRNA processing includes capping (5’ cap), polyadenylation (3’ Poly A tail), and splicing (removal of introns).

Prokaryotic ribosomes consist of two unequally sized subunits, large and small, which form a complete ribosome unit.

Translation is the process in which RNAs are "read" by ribosomes, and the appropriate protein is made.

DNA from the chromosomes first undergoes transcription to generate RNA. This RNA then undergoes translation, which is the process by which the genetic code is used to make necessary proteins.

The mRNA will be complementary to the DNA sequence, but remember that mRNA has a uracil (U) base instead of thymine (T). If the base on the left is the DNA, the corresponding mRNA code is:

UAAUCGUG

The DNA template strand will be complementary to the DNA coding strand sequence. If the base on the left is the coding DNA, the corresponding template DNA strand code is:

TGACAATG

Helicase is the enzyme that breaks the bonds between the coding and template strands of DNA so that the other DNA replication machinery can access the codes. The other functions listed are important roles, but can be attributed to other enzymes.

The central dogma of biology dictates that the coded genetic information stored in DNA is transcribed into single stranded RNA, which is then translated into protein.

The central dogma of biology reads that DNA goes to RNA which goes to protein. All of the following do that except for HIV, which uses reverse transcriptase in order to convert RNA to DNA which is going in reverse of the central dogma.

Given the definition that a gene is the segment of DNA necessary to create a protein, we can immediately eliminate the choices of "Poly-A tail and 5' cap" and "Length of DNA from a single chromosome." Neither of these choices correspond to a segment of DNA: the first corresponds to segments of processed mRNA, and the second to the entire length of the DNA unsegmented. Neither "DNA encoding mRNA" or "Promoter region of DNA" can be correct, as they cannot function without the other, with the promoter region allowing proteins to prepare for transcription of the DNA-encoding mRNA to be produced.

The promoter region of DNA does not interact with the shape of the DNA around it, eliminating all choices where change in DNA shape occurs. This leaves the answer choices of "To be a template for the mRNA strand," and "To initiate transcription of a particular gene." The promoter region is not transcribed to the mRNA that it initiates, leaving the correct answer, "To initiate transcription of a particular gene." The promoter region does this by attracting transcription factors necessary for recruitment of RNA polymerase.

The central dogma of biology occurs inside of the nucleus from DNA to modified mRNA transcripts prepared to be exported to the cytoplasm. Since the nucleus is an organelle separated from the endoplasmic reticulum and the mitochondria, those answers can be eliminated. Translation occurs on ribosomes, not transcription. It is an important distinction that transcription occurs entirely within the membranes of the nucleus, and would not be found on the outer membrane of the nuclear envelope.

In the central dogma of biology, DNA is transcribed to RNA, which is then translated to proteins. DNA and RNA are made up of nucleotides, and proteins are made up of amino acids. The only answer choice that does not fit this sequence is "RNA is transcribed into proteins." A correct statement would be that RNA is translated into proteins.

Translation occurs on ribosomes in the cytoplasm or attached to the rough endoplasmic reticulum. No part of transcription or translation occurs in the mitochondria. Transcription occurs in the nucleus of the cell and therefore "nucleus . . . transcribed" is the correct answer.