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BIOL 3080 Lecutre 1 - Biology Study Notes

The Universal Features of Cells on Earth

  • Cells share similar structures and metabolic pathways.

All Cells Store Their Hereditary Information in the Same Linear Chemical Code: DNA

  • Building Block of DNA:

    • Composed of a phosphate group, sugar, and base.

    • Nucleotide: The monomer that makes up DNA, consisting of these three parts.

Differences Between DNA and RNA

  • Sugar Component: 2' OH group in RNA makes it more reactive than DNA.

  • Bases:

    • Purines (double ring): Adenine (A), Guanine (G)

    • Pyrimidines (single ring): Cytosine (C), Thymine (T - only in DNA), Uracil (U - only in RNA)

  • RNA Components: Consists of ribose sugar, uracil instead of thymine.

  • DNA Components: Consists of deoxyribose sugar, thymine as a base.

Structures of DNA

  • DNA is composed of purines and pyrimidines.

  • Double-stranded structure forms through complementary base pairing:

    • Example DNA Sequence:

      • Strand: 5'-A G T A G G C T C A-3'

      • Complement: 3'-T C A T C C G A G T-5'

  • Hydrogen bonds between bases:

    • Adenine pairs with Thymine (A-T)

    • Guanine pairs with Cytosine (G-C)

Functions of DNA

  • Acts as a template for the replication.

  • During replication, the two strands of a DNA double helix are separated; each strand serves as a template for a new strand.

RNA Synthesis

  • Cells transcribe portions of their hereditary information into RNA through a process called transcription.

  • mRNA is synthesized from DNA, followed by the translation of RNA to form proteins.

The Role of Proteins

  • All cells use proteins as enzymes to catalyze chemical reactions, evidenced by enzymes like lysozyme.

Gene Transfer and Function

  • Genes can be transferred between organisms thus playing roles in heredity and evolutionary biology.

  • Each protein is encoded by a specific gene.

  • Genes can also code for functional RNA.

  • Viruses can facilitate gene transfer between eukaryotic hosts, and gene mixing occurs during sexual reproduction.

Gene Families Across Domains

  • Table features gene families common to Archaea, Bacteria, and Eukarya across various functions:

    • Information processing, metabolism, translation, etc.

    • Example counts include:

      • Translation: 63 genes

      • Energy production: 19 genes

Comparative Cell Biology: Prokaryotes vs Eukaryotes

  • Prokaryotic Cells:

    • Size: Small (1-2 µm), high surface area to volume ratio, no organelles.

    • Contains ribosomes, plasma membrane, etc.

  • Eukaryotic Cells:

    • Size: Larger (10-20 µm), contains organelles like nucleus and mitochondria.

    • Lower surface area to volume ratio compared to prokaryotic cells.

Understanding Biochemical Diversity Among Prokaryotes

  • They exhibit various shapes:

    • Spherical (Cocci), Rod-shaped (Bacilli), Spiral (Spirilla), etc.

The Tree of Life and Evolution

  • Three primary branches: Bacteria, Archaea, and Eukaryotes.

  • Model organisms help elucidate fundamental biological mechanisms:

    • E. coli: Key for understanding DNA replication and protein synthesis.

Genome Complexity in Different Organisms

  • Eukaryotic genomes are larger than prokaryotic genomes:

    • Examples of genome sizes:

      • E. coli: 4.6 million nucleotide pairs

      • Human: ~3.2 billion nucleotide pairs

  • Table includes organisms like:

    • Saccharomyces cerevisiae (yeast): ~13 million nucleotide pairs.

    • Arabidopsis thaliana (plant): ~220 million nucleotide pairs.

Eukaryotic Genomes and Model Organisms

  • Model plants like Arabidopsis are widely used due to their small size and fast life cycle.

  • Fruit Fly (Drosophila melanogaster): Provides insights into vertebrate development and gene functions.

  • Zebrafish: Transparent embryos aid in the study of development.

Chromosomal Structures and Functions

  • Eukaryotic DNA is packaged into chromosomes, each containing long strings of genes.

  • The organization requires centromeres, telomeres, and replication origins.

Nucleosomes and Chromatin

  • Nucleosomes consist of DNA wrapped around histone proteins, forming the basic unit of chromosomal structure.

  • Chromatin exists in forms:

    • Heterochromatin: Tightly packed, often inactive.

    • Euchromatin: Lightly packed, typically active in transcription.

Gene Expression and Regulation

  • Genes contain introns and exons. Exons are retained in matured mRNA while introns are removed.

  • Gene regulation through histone modification can affect gene expression.