Key Concepts in Protein Synthesis and Mutations

Amino Acid

The building blocks of proteins; there are 20 different amino acids that combine in various sequences to form proteins.

Anticodon

A sequence of three nucleotides on tRNA that pairs with a complementary codon on mRNA during translation.

Cap

A modified guanine nucleotide added to the 5' end of mRNA, aiding in stability and recognition by ribosomes.

Codon

A sequence of three nucleotides on mRNA that codes for a specific amino acid.

Dehydration synthesis

Chemical Reaction in which water is removed to join two molecules together, often forming a peptide bond between amino acids.

Exon

A coding region of RNA that is expressed and translated into a protein.

Genetic Code

The set of rules by which information encoded in mRNA is translated into proteins, consisting of codons.

Intron

A noncoding region of RNA that is removed during RNA processing before translation.

mRNA

Messenger RNA; the type of RNA that carries genetic information from DNA to the ribosome for protein synthesis.

Peptide Bond

The bond that forms between two amino acids during protein synthesis, linking them together.

Polysome

A complex formed by multiple ribosomes attached to a single mRNA molecule, allowing for simultaneous translation.

Initiation of Translation

1st stage of translation where the small subunit of the ribosome binds to site, then travels from 5' to 3' until reaches start codon (AUG).

Elongation of Translation

2nd stage of translation where the initiator tRNA attaches to P site, new tRNA's go to A site.

Termination of Translation

The end of translation where the ribosome reaches a stop codon (UAA, UAG, UGA).

Polyadenylation

The addition of a poly-A tail (a series of adenine nucleotides) to the 3' end of pre-mRNA, enhancing stability and export from the nucleus.

Promoter

A sequence of DNA that signals RNA polymerase where to start synthesizing RNA.

Release Factor

A protein that recognizes stop codons (UAA, UAG, UGA) during translation and facilitates the termination of protein synthesis.

Ribosomes

Cellular structures where protein synthesis occurs, composed of rRNA and proteins.

RNA Processing

The modifications that pre-mRNA undergoes, including splicing, capping, and polyadenylation, to become mature mRNA.

RNA Polymerase

The enzyme that synthesizes RNA by transcribing the DNA template into RNA.

rRNA

RNA that makes up part of the ribosome (the organelle that translate the mRNA).

snRNA

Small nuclear RNA that makes up part of the spliceosome and facilitates mRNA splicing.

Stop Codon

A codon that signals the termination of protein synthesis; examples include UAA, UAG, and UGA.

tRNA

Transfer RNA; the type of RNA that carries amino acids to the ribosome during translation.

Translation

The process of converting mRNA into a specific sequence of amino acids to form a protein. Uses tRNA and rRNA, and located in the cytoplasm.

Terminator

A sequence of DNA that signals RNA polymerase to stop synthesizing RNA and detach from the DNA template.

tRNA synthetase

Enzyme that adds amino acids to the tRNA.

Aminoacylation

Process in which the correct amino acids are added to its tRNA by the enzyme aminoacyl-tRNA synthetase.

Transcription

The process that turns DNA into a strand of mRNA that will be later used in translation to make proteins.

Initiation of Transcription

1st step of transcription where RNA Polymerase starts where the promoter says it should start (start of DNA). The polymerase then stretches open the 2x helix and begins synthesis of a RNA strand complementary to one of the DNA strands.

Elongation of Transcription

2nd step of transcription where RNA polymerase moves along the DNA, and adds a 3' end of the RNA strand. This moves from 5' to 3' and the synthesis is single stranded.

Termination of Transcription

Final step of transcription where the terminator ends RNA polymerase from making RNA, in which it will fall apart. This makes: Pre-mRNA. It will later have a Poly A tail and cap so it can leave the nuclear pore, become mRNA, and enter the cytoplasm to start translation and make proteins.

Protein Synthesis Overview

Generalized process where DNA is compiled into mRNA in the Nucleus, in which the mRNA attaches to the ribosome. tRNA will bring amino acids to the ribosome by attaching specific mRNA codons. Amino Acids bond using peptide bonds, to create a protein (polypeptide).

Start Codon

The codon (AUG - Methionine) that initiates the start of translation.

Stop Codon

The codons (UGA, UAA, UAG) that tell the terminator to stop all continuing processes of translation.

Effect of Protein Shape

The sequence of amino acids determine the proteins shape. Proteins fold into specific shapes due to the order of the amino acids, which is determined by the DNA base sequence. A protein's shape also determines its function like enzymes, hormones, antibodies, etc.

Cystic Fibrosis

Lung impacting conditions where the CFTR gene has a 3 base deletion mutation. This causes lack of transportation of chloride ions and a CFRT protein to be built in cells that line the lungs and pancreas. This creates a sticky, thick mucus that causes respiratory problems, which can sometimes be fatal. It takes 2 copies of the gene to show symptoms, and is found on chromosome 7.

Mutations

Changes in the DNA base sequence (A, T, C, G) that lead to changes in the protein's shape. Different order of bases → different amino acids → different protein shape → different protein function. Takes place during DNA replication.

Substitution

Single base change mutation. Ex. ATC TAG → ACC TAG.

Deletion

Mutation that removes one or more bases. Ex. ATC TAG → ATT AG.

Adding/Insertion

Mutation that is adding one or more bases. Ex. ATC TAG → ATT CTA G.

Point Mutation

A substitution of a single base pair. Changes only one amino acid (if any).

Frameshift Mutation

Mutation where a single base is added or deleted, changes every amino acid after the mutation site.

Gametes

Sex cells that can pass mutations from one generation to another.

Mutagenic Agents

Mutations that are cancer causing. Ex. Chemicals, UV radiation, X-ray radiation.

Silent Mutation

Mutation where one codon is changed by the codon codes for the same Amino Acid, so no changed protein.

Missense Mutations

Codon is changed to a different Amino Acid which changes the protein structure.

Nonsense Mutation

Codon changes to a premature stop codon so translation stops too soon.