Cell Cycle Flashcards
How long do mammalian cells take to divide?
~24 hours.
What are the major stages of the cell cycle?
Interphase Prophase Metaphase Anaphase Telophase
What is mitosis?
Cell division which occurs in all somatic cells (except those involved in egg and sperm production).
Produces 2 identical daughter cells which have the same genetic content as the parent cell.
What is meiosis?
Cell division which occurs exclusively in the gonad. Replication occurs as in mitosis but 2 successive cell divisions occur so that the resultant cells only have half the genetic content of the parent cell e.g. 23 chromosomes.
Reduction division.
How does meiosis achieve genetic variation?
Recombination between chromosomes - this shuffles genetic information creating new combinations of genes on a chromosome.
Independent assortment - homologous chromosomes independently move to each pole during first meiotic division. This ensures mixing of genetic characteristics.
What happens at meiosis I and II?
Meiosis I - replication and first division of homologous chromosomes.
23 chromosomes go to each daughter cell following crossing over and independent assortment.
Meiosis II - much like mitosis. Replicated chromosomes divide at the centromere and sister chromatids separate and are divided into 2 daughter cells.
Total number of haploid cells - 4.
What is a major difference between meiosis in the female v the male?
Male meiosis produces 4 viable sperm whereas female meiosis produces 1 x egg and up to 3 polar bodies.
At what stage does meiosis in the female pause until sexual maturity?
Diplotene of prophase I. This resting phase is termed dictyotene.
What are the 5 stages of prophase I in meiosis I? Comment on anything of note that occurs.
Leptotene
Zygotene (chromosomes pair up and form bivalent, held together by synaptonemal complex)
Pachytene (chromosomes held in very close contact - physical exchange of material aka crossing over or recombination)
Diplotene (chromosomes repel but stay attached at chiasmata, female meiosis holds from here aka dictyotene - this lasts 15-45yrs)
Diakenesis (chiasmata holding them together move to the ends, cell enter remaining stages of meiosis I)
What is imprinting?
Mechanism by which a gene is expressed dependant on which parent it has been inherited from e.g. mat v pat
What are the different stages of the cell cycle? Briefly, what happens at each?
G0 - non-cycling stage
G1 - cell produces components needed for DNA synthesis
S - synthesis of DNA
G2 - period of growth before cell division
M- metaphase or cell division
Does DNA synthesis occur simultaneously for all chromosomes?
No. Areas replicate at different times, for example an inactivated X always replicates late.
These set times are consistent within a cell type but differ between cell types.
