MCBG Session 4 - Meiosis and Mitosis Flashcards
Briefly discuss the phenomena of missegregation in meiosis.
- 30% of human meiosis is faulty
- Consequences are: miscarriages and infertility
How can chromosome analysis be performed?
- Metaphase spread
- Stained metaphase chromosomes
- Actively dividing cells are needed
Outline the format of karyotyping.
- Standard format to describe the karyotype
- Chromosome number, sex complement and structural changes, separated by commas. For example:
I. 46, XX - normal female
II. 46, XY - normal male
III. 47, XY, +21 - male with trisomy 21
- No spaces in the karyotype
Outline mitotic non disjunction & its effects.
Outline mosaicism.
- Mosaicism: the presence of two/more cell lines in an individual. It can occur throughout the body or be tissue limited.
- The degree of mosaicism depends on when:
I. The first post-zygotic division occurs
II. Later mitotic divisions occur
Discuss role of mitotic spindle in mitosis and in cancer proilferation.
- The mitotic spindle ensures the accuracy of chromosome segregation. Chromosome segregation occurs on the microtubule-based mitotic spindle.
- The mitotic spindle is a proven target for successful cancer treatment. These treatments interfere with microtubules, preventing the cell from dividing hence stopping rapidly dividing cells such as cancer cells.
- Human cells are diploid. Homologous chromosomes only ever pair up during meiosis. In mitosis, sister chromatids pair up. However, most cancer cells are aneuploid and exhibit chromosome instability.
Discuss the role of TSG.
- Tumour suppressor genes (TSG) stop cancer growth.
- Oncogenes promote cancer.
- Centrosome amplification is often seen in conjunction with oncogene and TSG mutation.
Discuss numerical chromosome instability (CIN).
- Mitotic errors promote numerical chromosome instability (CIN) and tumour heterogeneity.
- Tumour heterogeneity leads to the ‘plasticity’ of cancer.
- Amplified centrosomes leads to multipolar spindles that promote CIN.
- Cancer cells frequently possess amplified centrosomes.
What is microtubule nucleation?
- The centrosome is the main site for microtubule nucleation in cells.
What regulates spindle polarity?
Spindle polarity is regulated by centrosome number.
What is cell clustering and what is the effect of it?
- Cancer cells have mechanisms to cluster amplified centrosomes.
- Clustering extra centrosome allow cancer cells to survive.
Explain therapeutic strategies around centrosome clustering.
Therapeutic strategies: inhibition of centrosome clustering.
