Question

Synapsis occurs between
a. mRNA and ribosome
b. Spindle fibres and centromere
c. Two homologous chromosomes
d. A male and female gamete

Answer 1

Synapsis occurs during phase I of meiosis. Sybenga suggested that there may be certain places (locations) called zygomers where mating begins. zygomeris can be present in large or small numbers. There are several places to start pairing.

Complete answer:
Let's study each option one by one

Option A:
Protein synthesis takes place within the Ribosomes. mRNA or Messenger RNA contains a genetic sequence of a gene. Synapsis is not observed between mRNA and ribosome. Thus it is an incorrect option.

Option B:
The centromere is a specialized DNA sequence of a chromosome that holds two chromosomes together. The center of the centromere consists of small disc-shaped structures called kinetochores. Spindle fibres are formed of microtubules and they are responsible for the separation of chromosomes into two daughter chromosomes by attaching themselves to the kinetochores. After the attachment chromosomes move to the spindle equator and later get migrated to opposite poles. Thus it is an incorrect option.

Option C:
During the Zygotene prophase I sub-stage of meiosis I, chromosomes begin to pair together and this process is referred to as synapsis. These pairs of chromosomes are known as homologous chromosomes. Therefore, option C is right.When observed under an electron microscope it can be observed that this synapsis is also accompanied by the formation of a complex structure made of protein-RNA complex called synaptonemal complex. The paired homologous chromosome containing the synaptonemal complex is called bivalent or tetrad. Thus it is a correct option.

Option D:
Synapsis is not observed between a male and a female gamete. Crossing over takes place between a male and a female gamete during prophase of meiosis. The point at which the crossing overtakes is called chiasma or chiasmata. The genetic material of the daughter cell differs from the parent cell because of crossing over. Thus it is an incorrect option.

Hence, the correct answer is option (C).

Note: Synaptonemal complexes are the structures of proteins formed during meiosis between homologous chromosomes and possibly mediating synapse and recombination during meiosis I in eukaryotes. It is currently believed that SC acts primarily as a scaffold to allow chromatid interactions to complete their crossing activity.The paired homologous chromosome containing the synaptonemal complex is called bivalent or tetrad.