a) Leptotene- It is the beginning of the prophase and the chromosomes appear as thin long threads. The condensation of chromosome is still not done by this phase. b) Zygotene- By this phase, the homologous chromosomes start pairing up and the chromosomes appear condensed and thick.
Are chromosomes thin?
After DNA replication, the chromatin condenses to form visible chromosomes which appear as long thin threads comprising pairs of replicated DNA molecules.
What is the main difference between chromatin and chromosomes?
Chromatin is a complex formed by histones packaging the DNA double helix. Chromosomes are structures of proteins and nucleic acids found in the living cells and carry genetic material. Chromatin is composed of nucleosomes. Chromosomes are composed of condensed chromatin fibers.
What stage do chromosomes appear?
Metaphase is a stage in the cell cycle where all the genetic material is condensing into chromosomes. These chromosomes then become visible. During this stage, the nucleus disappears and the chromosomes appear in the cytoplasm of the cell.
What is the pachytene stage?
Pachytene is a lengthy phase, lasting about 12 days in the rat; during this time there is a marked increase in cellular and nuclear volume. As the cells enter diplotene and diakinesis, the chromosomes begin to separate and condense further while synaptonemal complexes disappear.