Meiosis Flashcards
What is meiosis?
Meiosis is the division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte.
In diploid cell how do chromosomes appear?
As homologous pairs
What are homologous pairs?
Are chromosomes of the same size, same centromere position and with the same sequence at the same loci.
What do the chromosomes consist of in Meiosis 1 - at the start
Consist of two genetically identical chromatids attached at the centromere
Stage 1 of meiosis 1
The chromosomes condense and the homologous chromosomes pair up
Stage 2 of meiosis 1
after the homologous chromosomes pair up
Chiasmata form at points of contact between the non-sister chromatids of a homologous pair and sections of DNA are exchanged.
What are linked genes?
Those that are on the same chromosome.
What is the result of crossing over?
Can result in new combinations of the alleles of these genes
What is the role of Chiasmata
are essential for the attachment of the homologous chromosomes to opposite spindle poles and their subsequent segregation to the opposite poles during meiosis I
Features of crossing over of DNA
This crossing over of DNA is random and produces genetically different recombinant chromosomes.
Stage 3 of meiosis 1
after chiasmata and DNA is exchanged - crossover
Spindle fibres attach to the homologous pairs and line them up at the equator of the spindle
What is the orientation of the homologous pairs at the equator?
Random
What is independent assortment?
Each pair of homologous chromosomes is positioned independently of the other pairs, irrespective of their paternal or maternal origin.
Stage 4 of meiosis 1
after spindle fibres attach and equator
The chromosomes of each homologous pair are separated and move towards opposite poles.
Stage 5 of meiosis 1
after chromosomes are separated
Cytokinesis occurs and two daughter cells are formed
