2.3 b) Meiosis Flashcards
What is meiosis?
the division of the nucleus which creates four gametes from a gametocyte
Meiosis is the ___ of the ___ which results in the production of ___ gametes from a ___ ___.
division, nucleus, haploid, diploid gametocyte
A gametocyte is a cell which ___ (by meiosis) to form ___.
divides, gametes
In diploid cells, chromosomes typically appear as ___ ___.
homologous pairs.
What are homologous chromosomes?
chromosomes of the same size, centromere position and sequence of genes at the same loci
(loci = specific point on chromosome)
Homologous chromosomes are chromosomes of the same ___, ___ ___, and sequence of ___ at the same loci.
size, centromere position, genes
Meiosis is split into which stages?
Meiosis I and Meiosis II
The chromosomes (which replicated ___ meiosis I) each consist of two genetically ___ chromatids, attached at the ___.
before, identical, centromere
During meiosis I the chromosomes ___ and the ___ chromosomes line up along…
condense, homologous, the equator of the spindle. (They line up perpendicular to the equator)
___ form at the points of contact between the non-___ chromatids of a ___ pair, and sections of ___ are ___.
Chiasmata, sister, homologous, DNA, exchanged
What is a chiasmata?
the point at which non-sister chromatids of a homologous pair touch/cross over, before sections of DNA are exchanged
The crossing over of ___-___ chromatids occurs at a chiasmata, resulting in new ____ of ___ in the affected ____.
non-sister,
combinations, alleles, genes
Linked genes are those in the ___ ___.
same chromosome (they are close together)
The exchange of DNA sequences at a chiasmata leads to the ___ of ___ of linked genes.
recombination, alleles. (Linked genes are more likely to stay together when sections of DNA are exchanged at the chiasmata -as they are close together)
The transfer of DNA at a chiasmata is ___, and produces genetically ___ recombinant ___.
random, different, chromosomes
Recombination is responsible for the production of genetically different ___.
gametes
Spindle fibres attach to the ___ ___ and line them up parallel to the…
homologous pairs, equator of the spindle
The ___ of the pairs of ___ ___ at the equator is ___.
orientation, homologous chromosomes, random
Each pair of ___ ___ is positioned ___ compared to the other pairs at the equator of the spindle.
They are arranged irrespective of their ___ or ___ origin.
This is known as ___ ___.
homologous chromosomes, independently, maternal, paternal.
independent assortment
What is independent assortment?
the fact that homologous chromosomes are positioned independent of the other pairs, regardless of its maternal or paternal origin.
Chromosomes of each ___ pair are separated, and move towards ___ ___ of the cell.
Then ___ occurs, creating two ___ ___.
homologous, opposite poles.
cytokinesis, daughter cells
In meiosis II, each of the two cells produced in ___ _, undergoes a further ___ in which the ___ ___ of each ___ are separated.
meiosis I, division, sister chromatids, chromosome.
At the end of meiosis II, a total of _, ___ cells are formed.
4, haploid (tho the cells produced in meiosis 1 were also haploid, just with two chromatids per chromosome)
What happens in meiosis I?
- the (homologous) chromosomes condense and line up along the equator.
- sections of DNA are exchanged between non-sister chromatids at the chiasmata.
- Spindle fibres attach to the homologous pairs and line them up along the equator of the spindle. (independent assortment happens)
- The chromosomes are pulled to opposite poles of the cell.
- cytokinesis happens, producing 2 haploid cells
What happens in meiosis II?
the 2 haploid cells produced in meiosis I divide into 4 haploid gametes
During the Prophase of Mitosis, the chromosomes (condense/decondense), and they (condense/decondense) during the Telophase.
At the start of Meiosis I, the chromosomes (condense/decondense).
Prophase: condense
Telophase: decondense
meiosis I: condense
