Lecture Notes: How DNA Results in a Trait

Introduction

• Discusses how DNA leads to traits, such as eye color.
• DNA contains genes that code for proteins, which in turn make pigments that give the trait.
• The process of creating proteins from DNA is known as protein synthesis.

Importance of Proteins

• Proteins are crucial as they:
  • Involved in transport and structure.
  • Act as enzymes.
  • Protect the body.
• Proteins are essential for life; they are constantly being made by cells.

Role of DNA and RNA in Protein Synthesis

• DNA is found in the nucleus of cells.
• Some DNA does not code for proteins (noncoding DNA); some genes are not always active.
• RNA is a nucleic acid, plays a vital role in protein synthesis.
• Protein synthesis consists of two main steps: Transcription and Translation.

Transcription

• Occurs in the nucleus.
• RNA polymerase: enzyme that transcribes DNA into a message.
• Result is mRNA (messenger RNA): carries the message from DNA.
• mRNA undergoes editing before it is functional.
• mRNA exits the nucleus to the cytoplasm.

Translation

• Occurs in the cytoplasm at the ribosome.
• Ribosome made of rRNA (ribosomal RNA), facilitates the building of proteins.
• tRNA (transfer RNA) carries amino acids, the building blocks of proteins.
• mRNA guides which tRNAs bring specific amino acids.
• tRNA reads mRNA in triplets, known as codons.

Codons and Anticodons

• Codons are sequences of three bases on mRNA.
• tRNA has anticodons that pair with mRNA codons.
• Example: mRNA codon AUG pairs with tRNA anticodon UAC, bringing in methionine (start codon).
• Codon chart helps identify which codon corresponds to which amino acid.

Building Proteins

• Amino acids are linked via peptide bonds forming a protein chain.
• Sequence determined by mRNA, originally transcribed from DNA.
• Process ends when a stop codon is reached.
• After translation, proteins may fold and undergo modifications.

Conclusion

• DNA is the ultimate director of protein synthesis, facilitated by mRNA, rRNA, and tRNA.
• Protein synthesis is a complex and fascinating topic.