Meiosis/Mitosis Flashcards
Why does meiosis end in haploid cells?
To keep the same number of chromosomes from generation to generation
How does meiosis achieve genetic diversity
crossing over - chiasmata
random assortment
Define mosaicism, what does degree of mosaicism depend on?
Two or more cell lines in an individual - depends on how early in the zygote the mitotic non-disjunction occurs. Earlier = more cells affected
What can non-disjunction in mitosis vs meiosis cause? When is the exception?
Mosaicism vs Aneuploidy. If non-disjunction occurs in the first zygotic mitotic division it will appear as aneuploidy not mosaicism.
When is one time you may see monosomy as viable?
If it is the X chromosome - Turners Syndrome
Mosaicism is an example of a ________ mutation
Somatic
Meiosis error is an example of a ________ mutation
Germline
Name 3 consequences (disease etc) of faulty meiosis
Miscarriage
Mental retardation
Infertility
Are Kleinfelters and Turners example of mosaicism or aneuploidy? Are they inherited?
Can be both. Aneuploidy in meiosis = more symptoms. So can be both germline and somatic mutations. Not inherited. Mostly infertile
What does degree of mosaicism depend on?
How early the mutation is - earlier = more cells affected
What is SRY?
Sex determining region on Y chromosome.
What are the relevance of PAR regions? What type of gene are they called?
PAR1&2 on XY are only regions that should be crossed over during meiosis as only homologous genes. Other genes are sex-linked. They are pseudoautosomal and are the regions that help line up X with Y in meiosis
Which is more severe, aneuploidy in sex chromosomes or autosomes?
Autosomes as they are more likely to be genes essential for life. Can survive with 1/3 chromosomes (with 2/3 in normal/Kleinfelters one X is usually inactivated anyway)
What is anaphase lag, what can anaphase lag cause? When is it useful?
It is delayed chromosome movement/faulty spindle attachment leading to aneuploidy or mosaicism. It is useful in trisomy rescue as can make the cell normal
What are microtubules made of?
Tubulin
What are amplified centrosomes? What can this cause? Why?
Increased number of centrosomes making the cell multipolar, happens in cancer cells. They do have a mechanism to help prevent it called clustering - helps reduce aneuploidy so cancer cells can live on. Number of centrosomes at each end determines polarity and where chromosomes will go. Inhibit cancer cell clustering as a therapeutic target - wouldn’t affect cells that don’t cluster i.e normal cells.
How would a cancer drug that targets tubulin help treat cancer? e.g. Paclitaxel
Microtubules prevented from assembling - Prevents metaphase/anaphase leads to mitotic arrest = prevents division of cancer cells, prolonged cell cycle arrest = apoptosis
What is the centrosome made up of?
Microtubules/Centrioles etc (whole organelle)
How can an increase in centrosomes add to cancer heterogeneity?
Increase in centrosomes = multipolar cell division = aneuploidy in cancer cells = mutations and genetic variation = tumour heterogeneity
What are 4 things that all lead to cancer plasticity (heterogeneity)?
- Aneuploidy
- Translocations
- DNA damage
- Treatment resistance - mutation
Name 3 tumour suppressors
APC, p5, BRCA1/2
Name 3 Oncoproteins
RAS, Myc
Name two viral proteins that can inactivate p53
E6/E7
Do cancer cells have active telomerase? What could you use this for? Whats the risk?
Yes - could target in treatment to increase cancer cell genetic instability = apoptosis. Risk of increasing tumour heterogeneity.
