Molecular and Cellular Basis of Life: Transcription and Genetic Inheritance

Flashcards covering key concepts of gene theory, transcription processes in prokaryotes, and enzyme functions in molecular biology.

Archibald Garrod (1902)

Recognized that alkaptonuria is inherited via a recessive allele and proposed that patients with the disease lacked a particular enzyme.

Beadle and Tatum (1941)

Researchers who used X-rays to create mutations in the bread mold Neurospora crassa to study nutritional mutations, leading to the "one gene – one enzyme" hypothesis.

One gene – one polypeptide hypothesis

The modified form of Beadle and Tatum's original hypothesis, acknowledging that genes encode individual polypeptide chains rather than just whole enzymes.

Central Dogma

The biological framework where genetic information stored in DNA is transcribed into mRNA, which is then translated into an amino acid sequence by ribosomes.

Transcription

The DNA-directed synthesis of RNA where only the template strand is used and thymine (T) is replaced by uracil (U).

Translation

The mRNA-directed synthesis of polypeptides taking place at the ribosome, requiring mRNA, rRNA, and tRNA.

Messenger RNAs (mRNA)

RNA molecules that encode the amino acid sequences of all the polypeptides found in the cell.

Transfer RNAs (tRNA)

RNA molecules that match specific amino acids to triplet codons in mRNA during protein synthesis.

Ribosomal RNAs (rRNA)

RNA molecules that serve as structural and functional constituents of the ribosomes.

DNA Template Strand

The antisense strand of DNA that serves as the guide for RNA polymerase during transcription.

DNA Coding Strand

The non-template (sense) strand of DNA which has the same sequence as the RNA transcript, except it contains T instead of U.

RNA Polymerase Holoenzyme

A large enzyme consisting of five core subunits ($a_2\beta\beta'\omega$) and a sixth subunit called $\sigma$.

Sigma ($\sigma$) subunit

The component of the RNA polymerase holoenzyme responsible for directing the enzyme to the promoter.

Beta ($\beta$) subunit

The main catalytic subunit of the bacterial RNA polymerase.

Omega ($\omega$) subunit

A subunit of RNA polymerase that appears to protect the enzyme from denaturation.

Upstream sequences

Bases preceding the transcript initiation site, which are given minus ($-$) prefixes.

Downstream sequences

Bases following the transcript initiation site ($+1$), which are given plus ($+$) prefixes.

Promoter

A specific DNA sequence, such as the $-10$ and $-35$ regions in E. coli, where RNA polymerase binds to initiate transcription.

Nus A

A protein that binds to RNA polymerase after the sigma factor is released, readying the complex for the elongation phase.

Rho ($\rho$)-independent terminators

Transcription terminators characterized by the formation of a hairpin structure at a palindromic sequence that do not require external protein factors.

Rho ($\rho$) factor

A $\sim 274\,kD$ homohexameric protein complex with ATPase and helicase activity that unwinds the RNA from the DNA template to terminate transcription.

rut site

The Rho utilization element; a CA-rich sequence where the $\rho$ factor binds to the RNA.

Footprinting technique

A method used to identify protein-DNA binding sites based on the premise that DNA bound by protein is protected from chemical or enzymatic cleavage.