Stages of meiosis Flashcards
(9 cards)
1
Q
Step of meiosis
A
Meiosis 1:
- prophase 1
- metaphase 1
- anaphase 1
- telophase 1
(cytokines)
Meiosis 2
- prophase 2
- metaphase 2
- anaphase 2
- telophase 2
(cytokines)
2
Q
Prophase 1
A
- Chromosomes condense and become
visable - Homologous chromosomes link together
- called synapsis
- each pair is a bivalent - Chromatids wrap around each other join
at points called chiasmata - At the chiasmata crossing over happens
- Nuclear membrane disintegrates
- Nucleolus has disappeared
3
Q
Metaphase 1
A
- Pairs of homologous chromosomes
arrange themselves at the equator of the
spindle
- in a homologous pair
- one chromosome from each parent - Lie at the equator randomly with either
facing the pole - the combination of chromosomes that
goes into each daughter cell is random
- independent assortment
- produces new genetic combinations
4
Q
Anaphase 1
A
- Chromosomes in each bivalent seperates
- Spindle shortens and pulls one of each
pair of chromosomes to each pole - Each pole receives one of each
homologous pair - Because of their random order in
metaphase 1 theres a random mixture of
chromosomes from both parents
5
Q
Telophase 1
A
In some species the nuclear envelope reforms and the chromosomes uncoils back to chromatid
In many species the chromosomes stay in their condensed form
6
Q
Prophase 2
A
- chromosomes condense and become
visible again - nuclear membrane disintegrates
- centrioles separate and create a new spine at a right angle to the old spindle
7
Q
Metaphase 2
A
- Chromosomes line up on the equator of
the spindle - Each chromosome attached to a spindle
fibre by its centromere - Independent assortment happens
because the chromatids can face either
pole
8
Q
Anaphase 2
A
- Spindle fibres shorten
- Centromeres separate and pulling the
chromosomes to opposite pole
9
Q
Telophase 2
A
- Chromatids lengthen at the poles
- No longer distinguishable in the
microscope - Spindle disintegrates
- Nuclear envelope and nucleolus re-forms
