GENETICS 2

Explain the role of transcription in gene expression and why transcription is essential for cellular function

Compare transcription and DNA replication in terms of

• template use

• Enzymes

• Nucleotide substrates

• Base-pairing rules

• Primer requirements

• Products

Distinguish the DNA template strand from the coding strand, and determine the sequence and direction of an RNA transcript from a DNA sequence

Describe the structure and functions of bacterial RNA polymerase, include roles of

• the core enzyme

• The holoenzyme

• Sigma factor

Identify the major features of bacterial promoter, including:

• the -35 region

• The -10 region (pribnow box)

• The +1 transcription start site

Explain their roles in transcription initiation

Explain the major molecular events of the three stages of prokaryotic transcription:

• initiation

• Elongation

• Termination

Compare rho-independent and rho-dependent termination. And explain how each mechanism causes transcription to end.

Promoter recognition → DNA opening → RNA synthesis → RNA elongation → termination

Initiation → elongation → termination

Finally:

DNA gene → RNA transcript

Define translation and explain its role in the flow of genetic information: DNA → RNA → protein

Define the genetic code and codon and explain how mRNA codons specify amino acids

Describe the major characteristics of the genetic code: triplet, unambiguous, degenerate, start/stop signals, commaless, nonoverlapping, and nearly universal

Use a codon table to determine the amino acid specified by an mRNA codon and identify start and stop codons

Identify the major requirements for translation and explain the roles of mRNA, ribosomes, and tRNA

Describe the bacterial 70S ribosome, including the 50S and 30S subunits and the role of 23S rRNA in peptide-bond formation

Identify the A, P, and E sites of the ribosome and explain the role of each

Describe tRNA structure and explain how the anticodon and amino-acid attachment site allow tRNA to function as an adapter

Determine the complementary codon-anticodon sequences and their correct antiparallel orientation

Recognize that tRNAs contain modified nucleotides, including pseudouridine and inosine

Explain the wobble hypothesis and how wobble allows one tRNA to recognize more than one synonymous codon

Explain the tRNAs are charged with amino acids and distinguish the bacterial initiator tRNA carrying fMET from tRNAs used at internal AUG codons

Describe the major stages of prokaryotic translation:

• initiation

• Elongation

• Termination

Explain the roles of 30S and 50S ribosomal subunits, the Shine-Dalgarno sequence, and translation factors during initiation

Explain how charges tRNAs enter the ribosome and move through the A, P, and E sites

Explain the roles of EF-Ty, EF-G, and 23S rRNA during elongation

Explain how release factors recognize stop codons and terminate translation

Describe the 4 levels of protein structure

Explain how protein folding contributes to protein function

Explain how protein misfolding can disrupt cellular function and contribute to disease

Recognize the diverse functions performed by proteins in cells

Explain why cells regulate gene expression and how regulation helps conserve energy and respond to environmental changes

Distinguish between constitutive and inducible gene expression

Compare positive and negative gene regulation and explain the roles of activators and repressors

Describe the organization of a bacterial operant and explain how multiple genes can be regulated together

Distinguish regulatory DNA sequences from regulatory proteins and explain the difference between cis-acting and trans-acting components

Identify the major components of the lac regulatory system, including the lack, the promoter, operator, lacZ, lacY, and lacA and describe their functions

Explain how the three lac structural genes are transcribed into one polycistronic mRNA but translated into three separate proteins

Explain how the lac repressor and allolactose regulate transcription when lactose is absent or present

Predict whether the lac operon is repressed or transcription is permitted under different lactose conditions

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