Biochemistry - DNA, Replication, and Translation Study Flashcards

Comprehensive vocabulary flashcards covering the flow of genetic information, DNA structure, replication enzymes, and the mechanism of protein translation.

Central Dogma of Biology

The golden rule of how genetic information flows: $DNA \rightarrow RNA \rightarrow Protein$.

Transcription

The step where information from $DNA$ is copied onto a messenger ($RNA$).

Translation

The step where the cell reads the messenger ($RNA$) to build a protein.

Nucleotide

The repeating building block of DNA, consisting of a phosphate group, a deoxyribose sugar, and a nitrogenous base.

Purines

Big, double-ring nitrogenous bases consisting of 9 atoms: Adenine (A) and Guanine (G).

Pyrimidines

Small, single-ring nitrogenous bases consisting of 6 atoms: Cytosine (C) and Thymine (T).

Complementary base pairing

The specific pairing where $A$ always pairs with $T$ (held by 2 hydrogen bonds) and $C$ always pairs with $G$ (held by 3 hydrogen bonds).

Semi-conservative model

The correct model of replication where each new DNA molecule consists of 1 old strand and 1 new strand, proven by Meselson and Stahl (1958).

Leading strand

The DNA strand built smoothly and continuously in one long piece, following the replication fork.

Lagging strand

The DNA strand built in short pieces called Okazaki fragments because it faces 'the wrong way' ($3'$ to $5'$ relative to the fork).

Helicase

The enzyme that unwinds and unzips the double helix at the replication fork.

Topoisomerase

The enzyme that relieves the strain and tension caused by unwinding just ahead of the replication fork.

Primase

The enzyme that lays down a short $RNA$ primer to provide a starting point for DNA polymerase.

DNA polymerase III

The main builder enzyme that adds DNA nucleotides to make the new strand.

DNA polymerase I

The enzyme that removes $RNA$ primers and replaces them with DNA.

DNA ligase

The enzyme that glues DNA fragments (such as Okazaki fragments) together into one continuous strand.

Codon

A chunk of 3 $RNA$ bases that acts as a code word for one specific amino acid.

Redundant

A feature of the genetic code where more than one codon can code for the same amino acid (64 codons for ~20 amino acids).

Unambiguous

A feature of the genetic code where each codon codes for only ONE amino acid.

AUG

The START codon which also codes for the amino acid Methionine.

Stop codons

Signals that end the protein synthesis; these include $UAA$, $UAG$, and $UGA$.

Anticodon

A 3-base section on the $tRNA$ that pairs with the matching codon on the $mRNA$.

Aminoacyl-tRNA synthetase

The enzyme that attaches the correct amino acid to a $tRNA$ using $ATP$ for energy.

Wobble

The relaxed rules for the third base of a codon, allowing one $tRNA$ to read more than one codon.

A site (Aminoacyl)

The ribosomal slot where the new incoming $tRNA$ (with its amino acid) arrives.

P site (Peptidyl)

The ribosomal slot that holds the $tRNA$ carrying the growing protein chain.

E site (Exit)

The ribosomal slot from which the now-empty $tRNA$ leaves.

Primary structure

The plain sequence of amino acids in order.

Secondary structure

Local folding of the amino acid chain into $\alpha$-helices (coils) and $\beta$-pleated sheets.

Tertiary structure

The whole amino acid chain folding into one 3D shape, held by forces like disulfide bonds between cysteines.

Quaternary structure

The final structural level where two or more folded amino acid chains (subunits) join into one functional protein.