The Cell Nucleus Flashcards
What are the functions of the nucleus?
- store and maintain the cells DNA
- DNA replication
- Transcription occurs in the nucleus
- Ribosomal Biogenesis
- Controls communication between the nucleoplasm and the cytoplasm
How many pairs of chromosomes does a human cell have?
Humans have 23 pairs of chromosomes.
What are the key structural features of a chromosome?
Contains telomeres, which protects the ends of chromosomes and maintain stability, and contains a centromere, which is needed during cell division as it holds sister chromatids together during G2 of the cell cycle, as well as making sure that the chromosomes are evenly divided between the two daughter cells. Finally it also contains replication origins (an area which replication is initiated).
How can we identify the different types of chromosomes visually?
By looking at the light and dark bands from the g banding, which helps us identify the type of chromosome but this is dependant on the location of the centromere.
What are the arms labelled as?
The ‘p’ arm is the top half whereas the bottom half is labelled as the ‘q’ arm.
What does metacentric, submetacentric and acrocentric mean?
Metacentric is when the ‘p’ arm length is equal to the length of the ‘q’ arm.
Submetacentric means when the ‘p’ arm is smaller than the ‘q’ arm.
Acrocentric is when the ‘p’ arm is much smaller than the ‘q’ arm.
What is the name of the technique used to visualise human chromosomes?
Karyotyping.
This technique is only used to see gross chromosomal abnormalities but cannot detect the small deletions, insertions etc.
What type of karyotyping can be used to visualise small deletions and insertions within chromosomes?
Spectral Karyotyping and this modern method uses a fluorescent dye.
How are chromosomes organised within the nucleus during metaphase?
They are condensed and tightly packed.
How are chromosomes organised within the nucleus during interphase?
They are relaxed and loosely packed.
How can chromosomes be seen during metaphase?
They can be seen using light microscopy and also using a technique called ‘FISH’ where a certain number of chromosomes have been tagged yellow.
Where is the location of the nucleus where it is gene-rich?
Periphery of the nucleus.
Where is the location of the nucleus where it is gene-poor?
Interior of the nucleus.
What is heterochromatin?
It is highly condensed chromatin which is found near centromeres and telomeres on chromosomes.
It is gene-poor.
It is highly condensed and is more resistant to gene expression.
It is also associated with the nuclear envelope.
A typical cell will have 10% of its genome made with heterochromatin.
What is euchromatin?
It is less condensed chromatin and is gene-rich.
Active genes are usually found within euchromatin.
A typical cell will have majority (90%) of its genome made with euchromatin.
