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# Learning Objectives - Understand DNA replication, transcription, and translation - Know differences between prokaryotes and eukaryotes - Understand gene expression regulation ## 1. DNA Structure & Replication **Structure:** Double helix, antiparallel strands, complementary base pairing (A-T, G-C).
Learning Objectives
- Understand DNA replication, transcription, and translation
- Know differences between prokaryotes and eukaryotes
- Understand gene expression regulation
1. DNA Structure & Replication
Structure: Double helix, antiparallel strands, complementary base pairing (A-T, G-C). Replication: Semi-conservative - each new DNA molecule has one original and one new strand.
2. Transcription (DNA -> RNA)
RNA polymerase reads template strand (3 to 5), produces mRNA (5 to 3). In eukaryotes: introns removed via splicing, exons joined. Alternative splicing: one gene -> multiple protein isoforms.
3. Translation (mRNA -> Protein)
Ribosome reads mRNA codons (3 nucleotides). tRNA brings matching amino acids. Start codon: AUG (Methionine). Stop codons: UAA, UAG, UGA. Polypeptide folds into functional protein.
4. Gene Expression Regulation
Transcription factors bind DNA to control transcription. Promoters: where RNA polymerase binds. Enhancers/silencers: distant regulatory elements. Epigenetics: DNA methylation, histone modifications.
Q1: What is the difference between exons and introns?Exons: coding regions that remain in mature mRNA and are translated to protein. Introns: non-coding regions removed by splicing. In humans, only ~2% of genome codes for proteins (exons). Q2: What is alternative splicing?One gene can produce multiple different mRNA transcripts by including different combinations of exons. Estimated 95% of human genes undergo alternative splicing, greatly expanding protein diversity from a limited genome. Q3: How does complementary base pairing work?A pairs with T (or U in RNA), G pairs with C. This enables DNA replication, transcription, and many bioinformatics algorithms to predict sequence complementarity and hybridization. Q4: What is a promoter?DNA sequence upstream of a gene where RNA polymerase binds to initiate transcription. Promoter sequences are key regulatory elements. Bioinformatics identifies promoter motifs (e.g., TATA box). Join Discord PreviousIntroduction to BioinformaticsNextSequence Alignment