Protein Synthesis Flashcards

Central Dogma

• Describes the flow of genetic information from DNA to RNA to protein synthesis.
• Involves transcription (DNA to mRNA) and translation (mRNA to protein).

Differences between DNA and RNA

• Type of Sugar: DNA contains deoxyribose; RNA contains ribose.
• Number of Strands: DNA is double-stranded; RNA is single-stranded.
• Nitrogenous Bases: RNA has A, C, G, U (uracil); DNA has A, T, C, G.

Types of RNA

• Messenger RNA (mRNA): Carries genetic instructions from DNA to ribosomes for protein synthesis.
• Ribosomal RNA (rRNA): Combines with proteins to form ribosomes, the site of protein assembly.
• Transfer RNA (tRNA): Transfers specific amino acids to ribosomes, matching anticodons with codons in mRNA.

Key Components in Transcription & Translation

• Promoter: A DNA region that indicates where transcription starts.
• mRNA Cap: A guanine modification at the 5' end that assists ribosome binding.
• Poly-A Tail: A stretch of adenine nucleotides that protects mRNA from degradation.

Ribosome Structure

• Composed of two subunits: one small and one large, facilitating protein synthesis.

Initiation of Translation

• Begins at the start codon AUG, with the corresponding tRNA bringing methionine as the first amino acid.

Polypeptide Assembly

• The ribosome facilitates the joining of amino acids, releasing tRNA to continue adding new amino acids from mRNA.
• Process continues until a stop codon is reached, resulting in a polypeptide.

Steps of Protein Synthesis

• DNA provides the template for mRNA formation.
• mRNA undergoes processing and carries codons.
• mRNA interacts with ribosomes in the cytoplasm.
• tRNA matches anticodons to mRNA codons, delivering amino acids.
• Peptide chains are formed through complementary base pairing and transferred between tRNAs.

Codons and Amino Acids

• There are 64 possible codons.
• 20 different amino acids are used to build proteins.

Polysomes

• Formation involves multiple ribosomes simultaneously translating the same mRNA, enabling rapid protein production.

Mutations

• Defined as errors in DNA replication, resulting in a change in the DNA sequence.
• Gene Mutations: Affect one or several nucleotides; include substitution, insertion, and deletion.
• Chromosome Mutations: Involve changes in chromosome number or structure.

Types of Mutations

• Substitution Mutation: A single base is replaced, potentially altering the gene product.
• Insertion Mutation: One or more nucleotides are added to a gene.
• Deletion Mutation: One or more nucleotide pairs are removed from a gene.