Meiosis (L14) Flashcards
How do cells ensure that each gamete receives exactly one copy of each chromosome pair?
Meiosis = meiosis ensures that haploid chromosomes are generated in the zygote.
What are the benefits of the sexual cell cycle?
- allow species to survive better under different pressures
- increase evolutionary flexibility
- decrease competition amongst offspring
Egg For the Couriers make them Better!
What are the phases of meiosis?
Interphase — Meiosis 1 — Meiosis 2
What happens in interphase of meiosis?
Pair of homologous chromosomes in diploid chromosome diploid means two sets - one from mum and one from dad
= a diploid cell with duped chromosomes
What happens in Meiosis 1?
Remember: all of the action occurs in meiosis 1.
the phases are all the same as mitosis but just slightly different
But meiosis 1 focuses on separating the homologous chromosomes so by the end of it, you have a haploid number of chromosomes. So only one pair of chromosomes!!
What happens during Prophase 1? Why is this a significant phase in Meiosis?
- the homologous chromosomes align and synapse
- crossing over occurs at Prophase = which is a great source of genetic variation
When two chromosomes line up and genetic information is being exchanged.
Crossing over / genetic recombinance
What is the difference between Metaphase of Mitosis and Meiosis? (There’s 2)
- for mitosis the centromeres line up. And there is a diploid number of chromosomes on the metaphase plate
- for meiosis the chiasmata line up. And there is a haploid number of chromosomes on the metaphase plate (to separate into individual chromatids)
What happens during Anaphase 1?
Homologous chromosomes separate or disjoin into sister chromatids
Why is the cell in Telophase known as haploid?
Because only half the genetic information is in each new cell.
What happens in meiosis 2?
sister chromatids separate during meiosis 2.
Remember: Meiosis 2 is a lot like mitosis. However it still produces a haploid number of daughter cells.
What are some key differences between Mitosis and Meiosis 1?
- Metaphase. In mitosis chromosomes align independently; in meiosis homologous chromosomes synapse to carry out crossing over
-Centromere = mitosis ; Chiasmata = meiosis
-Disjunction. In mitosis chromatids disjoin 2n => 2n
In meiosis chromosomes disjoin 2n => n
-Daughter cells in mitosis => identical to parent species; daughter cells in meiosis => non identical to parent species
How does sexual reproduction produce genetic diversity?
Independent assortment of chromosomes
Crossing over
Random fertilisation of genes
Crossing over occurs between what?
Non sister chromatids
When can non-disjunction occur?
Anaphase 1 & 2
