From DNA to RNA to Protein

From DNA to RNA to Protein

• DNA holds genetic instructions for cells and organisms.
• Genotype is the genetic makeup (DNA sequence).
• Phenotype is the physical traits (result of protein actions).
• Proteins are built according to instructions in DNA.
• DNA dispatches instructions through RNA, initiating protein synthesis.
• Molecular command flow: DNA (nucleus) → RNA → protein synthesis (cytoplasm).
• Transcription: Transfer of genetic information from DNA to RNA.
• Translation: Transfer of information from RNA to a polypeptide (protein).
• Genes dictate polypeptide production. Information flow is from gene to protein.

How an Organism's Genotype Determines its Phenotype

• Genotype: Heritable information in DNA nucleotide sequence.
• Phenotype: An organism's physical traits, resulting from the protein's action.
• Structural proteins build an organism.
• Enzymes catalyze chemical reactions vital for life.
• RNA carries DNA's instructions for protein synthesis.
• Transcription takes genetic information from DNA to RNA.
• Translation takes information from RNA to a polypeptide (protein strand).

Nucleotides to Amino Acids: An Overview

• DNA and RNA are polymers made of monomers (nucleotides).
• DNA monomers use A, T, C, G nitrogenous bases.
• RNA monomers use A, U, C, G nitrogenous bases.
• Genes are specific DNA base sequences; lengths are thousands of bases.
• Transcription is rewriting the DNA base sequence as RNA.
• Newly formed RNA nucleotides are complementary to DNA.
• RNA directs amino acid sequence in polypeptide.
• Polypeptides are polymers made of 20 common amino acids.

The Genetic Code

• Genetic code: Converting RNA nucleotide sequence to amino acid sequence.
• 61 triplets in RNA code for amino acids.
• AUG (methionine) signals polypeptide start.
• UAA, UAG, UGA are stop codons.
• Codons are three-base units in DNA, transcribed into RNA, and then translated into amino acids.
• Codons dictate specific amino acids in the polypeptide chain.
• Genetic code is nearly universal.

Transcription: From DNA to RNA

• Transcription is copying one recipe (gene) onto an index card (RNA).
• DNA strands separate where the process begins.
• Only one DNA strand is a template for new RNA.
• RNA nucleotides follow base-pairing rules (A with U, G with C).
• RNA polymerase links RNA nucleotides.
• Promoter is the "start transcribing" signal in DNA.
• Elongation is the RNA growing longer (RNA peels from template).
• Termination is RNA polymerase reaching the terminator sequence.
• RNA polymerase disconnects and DNA strands rejoin.

Translation: The Process

• Translation involves three phases: initiation, elongation, and termination.
• Initiation involves mRNA, first amino acid, and ribosome subunits.
• Elongation adds amino acids one at a time.
• tRNA delivers amino acids to the ribosome.
• Termination happens when a stop codon reaches the ribosome.
• The polypeptide is released and the ribosome subunits separate.

Mutations

• Mutations are changes in the genetic information.
• Mutations involving nucleotide substitutions can be silent (no effect), missense (one amino acid change), or nonsense (premature stop codon).
• Insertions or deletions (frameshift mutations) disrupt all codons downstream causing potential nonfunctional polypeptides.

Ribosomes

• Ribosomes are organelles in the cytoplasm responsible for polypeptide synthesis.
• Ribosomes are made of proteins and ribosomal RNA (rRNA).
• Ribosomes have binding sites for mRNA and tRNA.
• Ribosomes hold mRNA and tRNA close together to join amino acids.
• tRNA molecules bring the appropriate amino acid to the ribosome.

The Processing of Eukaryotic RNA

• Eukaryotic cells modify RNA transcripts before translation.
• Modifications often include the addition of a cap and tail.
• Introns (non-coding regions) are removed; exons (coding regions) are joined.
• RNA splicing joins exons to produce a continuous coding sequence.

This quiz explores the essential processes of molecular biology, detailing the flow of genetic information from DNA to RNA and then to proteins. It covers concepts such as genotype, phenotype, transcription, and translation, highlighting their roles in an organism's biology. Test your understanding of how genetic instructions dictate physical traits and protein synthesis.