Introduction to Molecular Biology

Molecular biology is the field of biology that studies the molecular basis of biological activity among biomolecules in the various systems of a cell, including the interactions between DNA, RNA, and proteins and their biosynthesis, as well as the regulation of these interactions.

Central Dogma of Molecular Biology

The central dogma of molecular biology, proposed by Francis Crick, describes the flow of genetic information within a biological system.

Main Processes

• DNA Replication: Duplication of DNA molecule for cell division
• Transcription: Creation of RNA from DNA template (DNA → RNA)
• Translation: Protein synthesis from RNA (RNA → Protein)

Relevance to Cancer

In the context of cancer, the central dogma is often dysregulated:

• DNA Mutations: Production of abnormal proteins
• Oncogenes: Mutated genes that promote uncontrolled growth
• Tumor Suppressor Genes: Inactivation leads to cancer development

Computational Applications

Sequence Analysis

Install Biopython once in your environment:

pip install biopython

# NOTE: Educational example only. Translation assumes the FASTA sequence
# is the coding strand and starts in the intended reading frame.
from Bio import SeqIO
from Bio.SeqUtils import gc_fraction

# Load DNA sequence
record = SeqIO.read("gene.fasta", "fasta")
dna_sequence = record.seq.upper()

# Basic analysis
print(f"Length: {len(dna_sequence)} bp")
print(f"GC content: {gc_fraction(dna_sequence) * 100:.1f}%")

# Keep only complete codons before translation.
trimmed_length = len(dna_sequence) - (len(dna_sequence) % 3)
coding_sequence = dna_sequence[:trimmed_length]

if trimmed_length != len(dna_sequence):
    print(f"Trimmed {len(dna_sequence) - trimmed_length} trailing base(s) before translation.")

# Transcription (DNA → RNA)
rna_sequence = coding_sequence.transcribe()
print(f"RNA: {rna_sequence[:50]}...")

# Translation (RNA → Protein)
protein = rna_sequence.translate(to_stop=False)
print(f"Protein: {protein[:20]}...")

Molecular Techniques

• PCR: DNA amplification
• Sequencing: Determination of base order
• Western Blot: Protein detection
• Northern Blot: RNA analysis

Learning Resources

• Books: Molecular Biology of the Cell (NCBI Bookshelf edition)
• Courses: MIT OpenCourseWare: Fundamentals of Biology, Coursera Bioinformatics Specialization
• Tools: NCBI, Ensembl, UniProt

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Understanding molecular biology is fundamental to understanding cancer, as the disease originates from molecular-level changes.