General Features of RNA Synthesis Quiz

DNA Replication

• DNA replication occurs at the origins of replication, where the double helix is unwound on both sides to form replication forks.
• Replication forks are the site where single-stranded DNA is exposed and DNA synthesis occurs.
• DNA replication can be bidirectional, with replication forks forming at either end of the bubble.
• The leading strand is always synthesized in the 5’ to 3’ direction.
• The lagging strand is replicated discontinuously as fragments, which are later joined to form a continuous strand.

Gene Expression

• The human genome encodes proteins, and genes encode 20,325 types of proteins.
• Gene expression requires several steps: transcription, translation, and protein synthesis.
• Transcription is the process of creating a messenger RNA that copies the DNA template that encodes a certain type of protein.
• Transcription factors are essential in transcription, as they interact and form an apparatus that binds DNA at certain sequences, initiate transcription, respond to signals from outside the cell, and link the genome to the environment.

The Central Dogma

• The Central Dogma is a theory that genetic information flows only in one direction, from DNA to RNA to protein, or RNA directly to protein.
• The Central Dogma is divided into three major parts: replication, transcription, and translation.
• The last step involves protein synthesis, in which amino acids are coded into proteins and their structure.

DNA Replication Hypothesis

• Three models of DNA replication were proposed: Semiconservative, Conservative, and Dispersive.
• The Semiconservative Model was demonstrated to be the correct mechanism by Matthew Meselson and Franklin Stahl in 1957 through the "Density Shift" experiment.

RNA Synthesis

• In transcription, the coding strand sequence is the same as the RNA sequence produced, except for Uracil replacing Thymine.
• The sense strand is the RNA sequence used to determine which amino acids are produced through mRNA.
• The template strand is the strand used for RNA synthesis of a particular RNA product.
• The antisense strand is the code complementary to the RNA produced.

Transcription

• Transcription is described in three steps: initiation, elongation, and termination.
• In transcription initiation, the binding of DNA polymerase to the promoter region occurs, which is recognized by the TATA binding protein.
• The TATA binding protein forms a pocket that allows RNA polymerase to bind and begin making RNA.

Protein Synthesis

• In translation, amino acids are formed from the instructions on the DNA.
• Proteins are classified into four basic structures or levels: primary, secondary, tertiary, and quaternary.
• Proteins fold into one or more three-dimensional shapes or conformations through folding, which is affected by attractions and repulsions between components.

Protein Structure and Folding

• Primary structure refers to the basic amino acid sequence.
• Secondary structure refers to amino acid sequences getting close together due to chemical reactions, forming loops, coils, barrels, helices, and sheets.
• Tertiary structure refers to larger structures formed from secondary structure, shaped by bonds between the R groups and their interaction with water.
• Quaternary structure consists of more than one polypeptide chain formed by bonds between several polypeptides.
• Chaperone proteins assist in precise protein folding by stabilizing partially folded regions and preventing proteins from getting stuck.
• Misfolded proteins can be degraded back into amino acids through the ubiquitin-proteasome pathway.