Figure 1. Early in prophase I, homologous chromosomes come together to form a synapse. The chromosomes are bound tightly together and in perfect alignment by a protein lattice called a synaptonemal complex and by cohesin proteins at the centromere.
Does homologous recombination occur in prophase 1?
Recombination occurs when two molecules of DNA exchange pieces of their genetic material with each other. One of the most notable examples of recombination takes place during meiosis (specifically, during prophase I), when homologous chromosomes line up in pairs and swap segments of DNA.
What are homologous chromosomes connected by?
Recombination. During MI, homologous chromosomes pair and are held together by synapses. Chiasmata form along the chromosomes at positions where genetic exchange or recombination takes place. These physical connections are important for keeping chromosomes together until they separate in anaphase I.
What are the chromosomes called in prophase 1?
During prophase I, homologous chromosomes pair and form synapses, a step unique to meiosis. The paired chromosomes are called bivalents, and the formation of chiasmata caused by genetic recombination becomes apparent. Chromosomal condensation allows these to be viewed in the microscope.
What is the function of prophase 1?
Prophase I highlights the exchange of DNA between homologous chromosomes via a process called homologous recombination and the crossover at chiasma(ta) between non-sister chromatids. Thus, this stage is important to increase genetic variation.
What does telophase 1 look like?
At each pole, during this stage, there is a complete haploid set of chromosomes (but each chromosome still has two sister chromatids). A cleavage furrow appears, and by the end of this stage the parent cell has divided into two daughter cells. This separation of the cytoplasm is called cytokinesis.
What does it mean when two chromosomes are homologous?
The two chromosomes in a homologous pair are very similar to one another and have the same size and shape. Most importantly, they carry the same type of genetic information: that is, they have the same genes in the same locations.