MBG: BLOCK 2: TOPIC 2: CHROMOSOME STRUCTURE AND FUNCTION

General/Background

• Chromatin: DNA and associated proteins in the nucleus, forms chromosomes.
• Chromosome: A highly organized structure of DNA and proteins that contains genetic material.
• Chromatid: One of the two identical copies of a chromosome, joined at the centromere.
• Chromosome Territories: Regions within the nucleus where chromosomes occupy specific positions.
• Histone: A protein that associates with DNA to form nucleosomes.
• Nucleosome: The basic unit of chromatin structure, consisting of DNA wrapped around a core of eight histone proteins.
• Centromere: A constricted region of the chromosome where spindle fibers attach during cell division.
• Kinetochore: A protein complex assembled at the centromere, which connects to microtubules during cell division.
• Neocentromere: A newly formed centromere at a different location on a chromosome.
• Telomere: Repetitive DNA sequences at the ends of chromosomes, protecting them from degradation.
• Karyogram: A visual representation of chromosomes arranged in order by size and shape.
• Karyotype: The characteristic chromosome complement of an individual or species.
• Autosome: Any chromosome that is not a sex chromosome (X or Y).
• Repetitive DNA: DNA sequences that are repeated many times in the genome.
• Pseudoautosomal Regions: Regions on the X and Y chromosomes that share homologous sequences.
• Banding/Banding Pattern: Distinctive patterns of light and dark bands on chromosomes, revealed by staining techniques.
• Euchromatin: Less condensed, gene-rich regions of chromosomes.
• Heterochromatin: Highly condensed, gene-poor regions of chromosomes.
• Locus (loci): The specific location of a gene on a chromosome.
• Allele: An alternative form of a gene.

Chromosome Structures and Function

• Types of DNA sequences: Different DNA sequences influence chromosome structure; repetitive DNA and gene-rich regions play a specific role.
• Chromosome structure and histone variants: Histone variants contribute to the formation of different chromosome structures.
• Chromosome Condensation:
  • Components: Histones, topoisomerases, and other proteins are involved in chromosome condensation.
  • Consequences of protein change: Alterations in protein availability or modifications impact condensation levels.
• Centromere:
  • Function: Attaches to spindle fibers during cell division, ensuring proper chromosome segregation.
  • Location: Constricted region of the chromosome.
  • Gene Content: Centromere contains unique repetitive DNA sequences and a few genes involved in centromere function.
  • Importance: Essential for proper chromosome segregation and cell division.
• Kinetochore:
  • Function: Attaches to microtubules, mediating chromosome movement during mitosis and meiosis.
  • Location: Attached to the centromere.
• Kinetochore, chromosome condensation, and centromere positioning:
  • A tightly regulated process, involving kinase activity and the Anaphase Promoting Complex (APC).
• Telomere:
  • Function: Protect chromosome ends from degradation and fusion, and regulate cell lifespan.
  • Length: Telomeres shorten with each cell division; telomerase enzyme adds nucleotides to the ends to prevent depletion.
  • Telomerase activity: Can be regulated by various factors, influencing cell ageing and proliferation.
  • Consequences of telomere change: Changes in telomere length affect cellular processes such as cell division, aging, and cancer development.
• Telomere Associated Proteins:
  • They protect telomeres and regulate telomerase activity.

Test your understanding of chromatin, chromosomes, and their structures with this quiz. Dive into essential concepts such as chromatids, histones, and the function of nucleosomes. This quiz will help reinforce your knowledge of cell division and genomic organization.