Medical Genetics: Central Dogma of Molecular Biology Review

RNA Processing

• The process of removing introns and splicing exons together is called splicing.
• A 7-methylguanosine cap is added to the 5' end of mRNA during capping.
• The main purpose of adding a polyadenylated tail to the 3' end of completed mRNA is to protect the mRNA from degradation and facilitate translation.

Genetic Code

• The genetic code reads as a sequence of codons that specify amino acids.

Translation

• The ribosome is responsible for forming peptide bonds between amino acids during translation.
• The process of adding an aminoacyl group to tRNA molecules is called aminoacylation.
• During the initiation stage of protein synthesis, the ribosome binds to the mRNA, and the initiator tRNA brings the first amino acid to the start codon.
• The ribosome holds mRNA, aminoacyl-tRNA, and the polypeptide chain in a correct orientation during translation.
• During the elongation stage of translation, amino acids are added to the polypeptide chain one at a time.
• At stop codons during translation termination, the ribosome releases the completed polypeptide chain.
• Polyribosomes (polysomes) are clusters of ribosomes translating a single mRNA molecule.
• tRNA brings amino acids to the ribosome during translation.

DNA Replication

• The enzyme helicase is responsible for unwinding the DNA double helix during replication.
• DNA synthesis occurs in the 5' to 3' direction.
• The enzyme DNA ligase is responsible for joining the Okazaki fragments on the lagging strand during DNA replication.
• The term 'semiconservative' in DNA replication means that each new DNA molecule consists of one old strand (template) and one new strand.
• The enzyme topoisomerase is responsible for relieving the tension ahead of the replication fork.
• The enzyme primase is responsible for adding RNA primers to initiate DNA synthesis.
• The role of DNA polymerase is to synthesize new DNA strands by adding nucleotides to the template strand.

Transcription

• The process of transcription is best described as: "Differs from DNA synthesis in that only one strand of DNA, the template strand, is used to make mRNA."
• RNA polymerase is the enzyme responsible for transcribing DNA into RNA.
• RNA synthesis proceeds in the 5' to 3' direction.
• A characteristic feature of gene structure during transcription is that the template strand is used to synthesize mRNA.