Chromosomes and Their Structure

Study Notes

Thread-like structures found in the nucleus of plant and animal cells.
Contain DNA, the basic genetic material passed from one generation to another.
Humans have 23 pairs
Chromosomes allow for the organization and transport of genetic material during cell division.

Centromere (or Kinetochore): Primary constriction in the center of a chromosome, where spindle fibers attach.
- This is critical for the movement of chromosomes during anaphase (cell division).
Chromatid: Each of the two identical halves of a chromosome joined by the centromere during cell division.
- Each chromatid contains DNA and is considered a separate chromosome strand.
Chromatin: A complex of DNA, RNA, and proteins found within the nucleus of eukaryotic cells.
- This complex forms the chromosomes.
- Chromatin is important for organizing the genetic material within the nucleus.
Secondary Constriction: Region involved in nucleolar organization.
- This constriction is present during cell division.
Telomere: The terminal region at each end of a chromosome.
- Telomeres protect the ends of chromosomes and play a role in aging.
Chromonema: A thread-like, coiled filament that controls the size of the chromosome.
- It contains gene-bearing chromomeres.
Chromomeres: Bead-like structures arranged along the chromonema.
- Contain genes which are constant in number for each chromosome.
Matrix (Pellicle): A jelly-like substance made of non-genetic material that surrounds each chromosome.
- Matrix holds the other components together.