· GENETICS – Terms – Chromosome
- Chromosome contains single DNA molecule packaged by various proteins
into a compact domain.
Chromosome is like ziped DNA.
- Stretched out DNA would form a very thin thread about 2 m long.
This DNA has to be packaged into the chromosome within a nucleus that
is much smaller than a printed dot.
At the point of maximum compaction, human chromosomes range in size
from about 2 to 10 micrometers in length.
- Chromosomes come in pairs of two.
Human has 46 chromosomes organized in 23 pairs.
- In idle phase chromosomes are not visible under the light microscope
because they are extremely thin.
During cell division, mitosis or meiosis, they become compacted into
shorter and thicker structures that can be seen under the microscope.
At this time they appear as paired rods with defined ends, called
telomeres, and they remain joined at a constricted region, the centromere.