Overview
This lecture compares DNA and RNA, highlighting their structures, functions, key differences, and importance in protein synthesis.
DNA vs. RNA: Structure and Location
- DNA and RNA are nucleic acids found in all living organisms.
- DNA is mainly located in the nucleus of eukaryotic cells, while RNA is found both in and out of the nucleus.
- Prokaryotic cells have DNA and RNA but no nucleus.
- Both DNA and RNA are made of nucleotides, each with a phosphate, sugar, and base.
- DNA is generally double-stranded and runs antiparallel; RNA is typically single-stranded.
- The sugar in DNA is deoxyribose; in RNA, it is ribose.
Nucleotide Bases and Pairing
- DNA bases: adenine (A), thymine (T), guanine (G), cytosine (C).
- RNA bases: adenine (A), uracil (U), guanine (G), cytosine (C); uracil replaces thymine.
- In DNA, A pairs with T and C pairs with G ("apples in the tree, car in the garage").
- In RNA, A pairs with U and C pairs with G.
Functions and Roles
- DNA stores genetic information and codes for traits.
- RNA is essential for protein synthesis by enabling the genetic message to be expressed.
- Three types of RNA: mRNA (messenger), rRNA (ribosomal), tRNA (transfer).
- mRNA carries messages from DNA to ribosomes.
- rRNA forms part of ribosomes, where proteins are made.
- tRNA brings amino acids to the ribosome, matching mRNA codons.
Protein Synthesis Overview
- mRNA is synthesized from DNA via transcription.
- Codon charts are used to match mRNA codons to amino acids.
- Amino acids are joined into polypeptide chains, which form proteins.
Sample Questions and Answers
- 8 DNA nucleotides have 8 bases and 4 base pairs.
- DNA strand "A, T, T, G, A, C" pairs with "T, A, A, C, T, G."
- For RNA, the complementary strand to "A, T, T, G, A, C" is "U, A, A, C, U, G."
Key Terms & Definitions
- Nucleotide — Building block of nucleic acids; consists of a phosphate, sugar, and base.
- Deoxyribose — The sugar in DNA nucleotides.
- Ribose — The sugar in RNA nucleotides.
- Antiparallel — Refers to the opposite orientation of the two DNA strands.
- mRNA — Messenger RNA; carries genetic instructions from DNA to ribosomes.
- rRNA — Ribosomal RNA; structural and functional component of ribosomes.
- tRNA — Transfer RNA; brings amino acids to ribosomes during protein synthesis.
- Transcription — Process of making an RNA copy from a DNA sequence.
- Codon — Sequence of three RNA bases that codes for an amino acid.
Action Items / Next Steps
- Watch the protein synthesis video for a detailed explanation of transcription and translation.
- Review linked supplemental materials for deeper exploration of DNA/RNA structure.