Meiosis Flashcards
What are some differences between meiosis and mitosis?
Meiosis results in haploid cells, mitosis diploid cells. In mitosis chromosomes line up on metaphase plate individually, in meiosis they line up paired. Mitosis has identical daughter cells whereas meiosis has genetically different daughter cells
How to chromosomes align in meiosis
Replicated chromosomes align to form a bivalent
What are chiasma?
This is the point at which chromosomes cross over, exchanging DNA, increasing genetic variation. Genes close together are less likely to be crossed
What is a holiday junction?
A cross-shaped structure that forms during the process of genetic recombination. It has the capacity to nick strands of DNA and rejoin them
On male Y chromosome where do you get recombination events?
On pseudoautosomal regions
Describe the activity of MPF during meiosis and what is it
MPF - Maturation promoting factor, it is a cyclin dependant kinase. There is high activity of MPF when chromosomes are separating
Describe the control of meiosis
Destruction of cyclin limits its activity, securin inhibits separase so must be degraded in order for chromosomes to be separated and degradation of cohesion complexes
Describe the loss of cohesion complexes in meiosis one and meiosis two.
Meiosis 1 - loss of cohesion complexes from the arms of the chromosomes but remain in the centrosome. In meiosis two there are loss of cohesion complexes in the centromere, allowing for chromosomes to separate
Describe some meiotic errors
Trisomy - Cells have an extra chromosome (Trisomy 21), or cells can have one (monosomy) or no chromosomes.
What is a uniparental heterodisomy mutation?
Occurs when a cell received both chromosomes from the one parent but are genetically different due to meiotic 1 error
What is a uniparental isodisomy?
Where both chromosomes come from one parent but are also genetically identical due to a meiotic 2 error
What is the relationship between meiotic errors and maternal age
the errors increase with maternal age
What is the difference between spermatogenesis and Oogensis
Spermatogenesis takes much less time than oogenesis
When does meiosis 2 occur in Oogenesis
not till after fertilisation
When does meiosis 1 finish?
After puberty
