BIOL 190A 1001 Final Study Guide: Molecular Genetics, Gene Expression, and Evolution

Ch. 13: DNA Structure, Replication, and Technology

DNA: History and Discovery

The discovery of DNA and its structure was a pivotal moment in biology, leading to the understanding of genetic inheritance and molecular biology.

• Key contributors: Chargaff, Hershey & Chase, Watson & Crick, Franklin, Meselson & Stahl

• DNA structure: Double helix composed of nucleotides (phosphate, deoxyribose sugar, nitrogenous base)

• Base pairing: Adenine (A) pairs with Thymine (T); Guanine (G) pairs with Cytosine (C)

Example: Watson and Crick's model explained how DNA could replicate and store genetic information.

DNA Replication

DNA replication is the process by which a cell copies its DNA before cell division.

• Meselson and Stahl experiment: Demonstrated semiconservative replication

• Replication bubble: Origin of replication where DNA unwinds

• Leading and lagging strands: Continuous vs. discontinuous synthesis

• Enzymes involved: DNA polymerase, primase, helicase, ligase

• Prokaryotic vs. eukaryotic replication: Multiple origins in eukaryotes, single origin in prokaryotes

Equation: $\text{DNA}_{\text{parent}} \rightarrow \text{DNA}_{\text{daughter}}$ (semiconservative model)

Chromatin Organization

Chromatin is the complex of DNA and proteins that forms chromosomes within the nucleus.

• Levels: Nucleosome, 30-nm fiber, looped domains, metaphase chromosome

DNA Technology

Modern DNA technology allows manipulation and analysis of genetic material.

• PCR (Polymerase Chain Reaction): Amplifies DNA segments

• DNA cloning: Inserting DNA into vectors for propagation

• Sequencing: Determining nucleotide order

• DNA fingerprinting: Identifying individuals based on DNA patterns

• CRISPR: Genome editing tool (general concept only)

Ch. 14: Gene Expression: From Gene to Protein

Gene Function and Expression

Genes encode instructions for building proteins, which perform cellular functions.

• Central Dogma: DNA → RNA → Protein

• Transcription: Synthesis of RNA from DNA template

• Translation: Synthesis of polypeptide from mRNA at ribosome

• Prokaryotes vs. Eukaryotes: Transcription and translation are coupled in prokaryotes, separated in eukaryotes

Equation: $\text{DNA} \xrightarrow{\text{transcription}} \text{mRNA} \xrightarrow{\text{translation}} \text{Protein}$

Properties of the Genetic Code

• Codon: Three-nucleotide sequence on mRNA encoding an amino acid

• Redundancy: Multiple codons can code for the same amino acid

• Start codon: AUG (methionine)

• Stop codons: UAA, UAG, UGA

RNA Types and Functions

• mRNA: Messenger RNA, carries genetic code from DNA to ribosome

• tRNA: Transfer RNA, brings amino acids to ribosome

• rRNA: Ribosomal RNA, forms ribosome structure

Mutations

• Point mutations: Single nucleotide changes (silent, missense, nonsense)

• Frameshift mutations: Insertions or deletions altering reading frame

Example: Sickle cell anemia is caused by a missense mutation in the hemoglobin gene.

Ch. 15: Regulation of Gene Expression

Prokaryotic Gene Regulation

Gene expression in bacteria is controlled by operons, which are clusters of genes regulated together.

• Lac operon: Inducible system controlling lactose metabolism

• Trp operon: Repressible system controlling tryptophan synthesis

• Positive vs. negative control: Activators increase transcription; repressors decrease transcription

Eukaryotic Gene Regulation

• Transcription factors: Proteins that bind DNA and regulate transcription

• Epigenetic modifications: DNA methylation, histone acetylation

• Post-transcriptional regulation: Alternative splicing, mRNA stability

Ch. 16: Development, Stem Cells, and Cancer

Development of Multicellular Organisms

Development involves cell division, differentiation, and morphogenesis.

• Cell differentiation: Cells become specialized for specific functions

• Gene regulation: Controls timing and location of gene expression

Types of Stem Cells

• Totipotent: Can form all cell types, including extraembryonic tissues

• Pluripotent: Can form most cell types

• Multipotent: Can form a limited range of cell types

Cancer

• Oncogenes: Mutated genes that promote cell division

• Tumor suppressor genes: Genes that inhibit cell division

• Mutations: Accumulation leads to uncontrolled cell growth

Ch. 17: Viruses

Virus Structure and Life Cycle

Viruses are non-living infectious agents composed of genetic material and a protein coat.

• Genetic material: DNA or RNA

• Capsid: Protein shell

• Life cycle: Attachment, entry, replication, assembly, release

Ch. 18: Genomes and Their Evolution

Genomics and Bioinformatics

Genomics is the study of whole genomes, while bioinformatics uses computational tools to analyze genetic data.

• Genome size and diversity: Varies among organisms

• Comparative genomics: Identifies similarities and differences across species

Mutation Type	Effect	Example
Silent	No change in amino acid	GAA → GAG (both code for Glu)
Missense	Change in amino acid	Sickle cell anemia (Glu → Val)
Nonsense	Premature stop codon	Cystic fibrosis (Gly → Stop)
Frameshift	Altered reading frame	Tay-Sachs disease

Additional info: These notes expand on the provided study guide by including definitions, examples, and key concepts for each chapter relevant to molecular genetics, gene expression, and evolution, as outlined in the original document.