Cell Pt. 2. Understanding the Cell Nucleus and Genetics

Sep 6, 2024

Lecture Notes on the Cell Nucleus and Genetic Code

Nucleus

  • Large, dark sphere in cells containing genes.
  • Most cells have one nucleus; exceptions:
    • Red blood cells: Do not have a nucleus.
    • Muscle cells: May have multiple nuclei due to fusion of cells during growth.
  • Essential for cell division; a cell must have at least one nucleus.
  • Surrounded by two membranes with pores, forming a boundary with the cytoplasm.

Nucleolus

  • Located inside the nucleus.
  • Functions as a factory for ribosomal RNA (rRNA).

Chromosomes and Genes

  • Chromosomes carry hereditary characteristics.
  • One gene codes for one protein.
  • Humans have 46 chromosomes (23 from each parent).
    • Diploid: Two sets of chromosomes.
    • Haploid: One set of chromosomes.
  • 30,000 to 40,000 genes packed in a DNA double helix (~2 meters long).
    • Organized by coiling around histone proteins.
    • Tightly wrapped during mitosis, forming visible X-shaped structures.
    • Centromere: The central point where the X shape crosses.

DNA and Genetic Code

  • DNA: Double helix formed by two nucleotide strands connected by hydrogen bonds.
  • Triplet/Codon: Three nucleotides in a row, coding for one amino acid.
  • Proteins are chains of amino acids.

Protein Synthesis

Transcription

  1. Identify and unwind the specific gene on the DNA.
  2. DNA remains in the nucleus; a copy (mRNA) is made and sent out.
  3. mRNA: Messenger RNA, a single-stranded copy of genetic information.

Translation

  1. mRNA exits the nucleus and enters a ribosome.
  2. rRNA (ribosomal RNA) reads nucleotide codons.
  3. tRNA (transfer RNA) brings amino acids from cytoplasm, attaching them to grow the polypeptide chain.

RNA Types

  • mRNA: Messenger RNA, carries genetic information from DNA to ribosomes.
  • rRNA: Ribosomal RNA, part of ribosomes, decodes mRNA.
  • tRNA: Transfer RNA, transports amino acids to ribosome.

Key Processes

  • Transcription: Copying DNA to mRNA using RNA polymerase.
  • Translation: Converting mRNA sequence to protein structure.

Remembering the Processes

  • Transcription: Transfer information from DNA to mRNA.
  • Translation: Convert genetic language (nucleotides) to protein language (amino acids).