Protein Synthesis and Gene Expression

• The study guide covers protein synthesis and gene expression (minimal biotech).

Sentence Stems

• mRNA is made during transcription.
• DNA is located in the nucleus.
• mRNA carries the genetic code from DNA to the ribosome.
• rRNA makes up the ribosome.
• RNA uses uracil instead of thymine.
• Amino acids make up a protein.
• Proteins are made at the ribosome.
• RNA can leave the nucleus.

Retroviruses and the Central Dogma

• The central dogma states that genetic information flows from DNA to RNA to protein.
• Retroviruses are an exception because they reverse this process.

RNA Structure

• RNA is single-stranded and contains ribose sugar, a phosphate group, and nitrogenous bases (Adenine, Guanine, Cytosine, Uracil).

Amino Acids

• There are 20 amino acids.
• Each amino acid has an amino group, carboxyl group, hydrogen atom, and R group attached to a central carbon.

mRNA Role

• mRNA carries genetic information from DNA to ribosomes for protein synthesis.

tRNA Role

• tRNA brings amino acids to the ribosome and attaches them to mRNA codons using anticodons.

rRNA Role

• rRNA is a structural component of ribosomes, aiding in amino acid bonding for protein creation.

mRNA and tRNA Relationship

• mRNA has codons, and tRNA has anticodons.
• This ensures amino acids bond to the mRNA codon sequence which consists of 3 nucleotides.

Transcription Location

• Transcription occurs in the nucleus for eukaryotic cells.

Transcription Process

• Initiation: RNA polymerase binds to the promoter region of DNA
• Elongation: RNA polymerase adds matching RNA nucleotides as it moves down the DNA.
• Termination: RNA polymerase reaches a stop sequence and releases the mRNA strand.

Eukaryotic mRNA Processing

• Eukaryotic mRNA is processed after transcription via 3 processes, including the 5' carbon cap; the Poly-A tail and Splicing
• Processing occurs because a modified guanine cap protects mRNA and helps ribosome binding, a sequence of adenine nucleotides adds to the 3' carbon for stability
• Introns are removed, and exons are joined.

Translation Location

• Translation takes place in ribosomes, either in the rough ER or cytoplasm.

Translation Process

• Initiation: A ribosome binds to mRNA, recognizing the start codon AUG.
• Elongation: tRNA brings amino acids to the ribosome, forming peptide bonds.
• Termination: The ribosome reaches a stop codon, releasing the completed protein.

Protein Synthesis Similarities

• Prokaryotic and eukaryotic protein synthesis both use mRNA, tRNA, the same genetic code, and ribosomes, with both conducting translation and transcription

Protein Synthesis Differences

• Prokaryotes lack a nucleus, so transcription and translation occur simultaneously.
• mRNA is not processed in prokaryotes after transcription.
• Eukaryotes are more complex and larger.

Prokaryotes and Human Proteins

• Prokaryotic cells can create human proteins through genetic engineering by inserting human genes into bacterial cells.

Frameshift Mutation

• A frameshift mutation involves nucleotides being inserted or deleted, shifting the reading frame.
• This can result in a new or dysfunctional protein.

Mutations

• Mutations can be neutral (no adverse effect), harmful (e.g., sickle cell disease), or beneficial (e.g., resistance to bacteria).

Gene Expression

• Gene expression leads to cell differentiation, where cells become specialized as genes are turned on or off.

Epigenetic Change

• An epigenetic change involves modifications to DNA that affect gene expression without changing the sequence.
• This can be caused by environmental factors, DNA methylation, or histone modifications.

Regulatory Proteins

• Regulatory proteins regulate gene expression; activators enhance transcription, while repressors suppress transcription.

Prokaryotic Systems

• Repressible systems in prokaryotic cells can be turned on and off as needed.
• Inducible systems are normally off but turn on through a stimulus.

Decoding DNA

• Use the DNA code to create the mRNA code.
• Use the mRNA code and the codon chart to determine the amino acid sequence.