Cytology I: The Nucleus Flashcards
(30 cards)
True or False. The nuclear membrane is not continuous with the rough endoplasmic reticulum of the cytoplasm.
False. It is.
Describe the nucleolus.
It is a non membrane bound structure, containing fibrils and granules rich in RNA. It is electron dense in the EM. Basophillic.
Where is the site of RNA synthesis and initial ribosomal assembly?
The nucleolus.
What are long tangled threads consisting of DNA, some RNA, and associated proteins.
A) Chromatin
B) Chromosones
What is euchromatin?
Dispersed, extended chromatin. It is present in the lightly stained regions of the nucleus and contains the potion of the genome actively being transcribed.
What is condensed, tightly coiled, regions of chromatin?
Heterochromatin.
How does heterochromatin appear in the microscope?
It appears electron dense in the EM and extremely basophilic in the LM.
Describe a euchromatic nucleus.
It is transcriptionally and metabolically active. Lot of dispersed chromatin and a large well developed nucleus.
Describe a heterochromatic nucleus.
It is transcriptionally and metabolically inactive. It has a lot of condensed, coiled chromatin and a small poorly developed nucleolus.
Describe Interphase.
- Nucleus appears normal.
- DNA is duplicated in the previous S phase.
- Copies of chromosomes are attached to centromeres.
- Two pairs of centrioles are present.
In what phase do chromosomes condense into a dark coil?
Prophase.
How does Prophase end?
With the disappearance of the the nuclear membrane and nucleolus.
In which phase do the chromosomes line up at the equator of the cell?
Metaphase.
In what phase are chromosomes the most condensed?
Metaphase.
When are chromosomes karyotyped?
Metaphase
Where do mitotic spindles attach to the chromosome?
They attach at the kinetochore.
What happens in Anaphase?
Sister chromatids split apart at the centromere forming two seperate chromosomes. They are then pulled to opposite poles.
When do chromosomes begin to uncoil and no longer be visible?
Telophase
How does Telophase end?
The nuclear membrane and nucleolus reform.
What is karyotyping?
The visualization of the number and morphology of the chromosomes of an individual.
What is the use of colcchicine?
It is added to the medium of dividing cells to block the cells in metaphase.
What is a Barr Body?
An inactivated X chromosome (sex chromatin)
What happens in G1?
Protein + RNA synthesis. Grow and perform specialized functions.
When does DNA synthesis and proteins associated with chromatin form?
S phase
