Molecular Biology Chapter: DNA Structure and Function

Study Notes

Process by which DNA makes a copy of itself
Semi-conservative replication: each new DNA molecule contains one old strand and one new strand
Steps:
1. Unwinding of double helix by helicase
2. Binding of primers to template strands
3. Synthesis of new strands by DNA polymerase
4. Proofreading and editing to correct errors

Process by which genetic information in DNA is used to synthesize RNA
Steps:
1. Binding of RNA polymerase to promoter region
2. Unwinding of DNA double helix
3. Synthesis of RNA complementary to template strand
4. Termination of transcription

Change in the DNA sequence
Types:
- Point mutation: substitution of a single nucleotide
- Frameshift mutation: insertion or deletion of nucleotides
- Chromosomal mutation: change in chromosome structure or number
Causes:
- Errors during DNA replication
- Exposure to mutagenic agents (e.g. radiation, chemicals)
Effects:
- Silent mutation: no effect on protein function
- Missense mutation: change in amino acid sequence
- Nonsense mutation: premature termination of protein synthesis

Complex of DNA and proteins that make up chromosomes
Structure:
- Nucleosome: DNA wrapped around histone proteins
- Chromatin fiber: series of nucleosomes
Functions:
- Packaging of DNA into nucleus
- Regulation of gene expression

Family of basic proteins that DNA wraps around to form chromatin
Types:
- Histone H1: links nucleosomes together
- Histone H2A, H2B, H3, and H4: core histones
Functions:
- Organization of DNA into chromatin structure
- Regulation of gene expression through histone modification (e.g. acetylation, methylation)