biology - 2.3b - meiosis Flashcards
What is meiosis?
The division of the nucleus that results in the formation of haploid gametes from a diploid gametocyte.
In diploid cells, what do chromosomes typically appear as?
Homologous pairs.
What are homologous chromosomes?
Chromosomes of the same size, same centromere position and with the same sequence of genes at the same loci.
What do the chromosomes, which have replicated prior to meiosis I, each consist of?
Two genetically identical chromatids attached at the centromere.
What happens to the chromosomes?
They condense and the homologous chromosomes pair up.
Where do 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 on the same chromosome
What can crossing over of the linked genes result in?
New combinations of the alleles of these genes.
What is this crossing over of DNA?
Random and produces genetically different recombinant chromosomes.
What do spindle fibres do?
They attach to the homologous pairs and line them up at the equator of the spindle.
What is the orientation of the pairs of homologous chromosomes at the equator?
Random.
How is each pair of homologous chromosomes positioned?
Independently of the other pairs, irrespective of their maternal and paternal origin. This is known as independent assortment.
What happens to the chromosomes of each homologous pair?
They are separated and move towards opposite poles.
What happens after the pairs of chromosomes are separated?
Cytokinesis occurs and two daughter cells form.
What happens in meiosis II?
Each of the two cells produced in meiosis I undergoes a further division during which the sister chromatids of each chromosome are separated.
