Question

Synapsis occurs between
A)Spindle fibres and centromere
B)Two homologous chromosomes
C)A male and female gamete
D)mRNA and ribosomes

Answer 1

Synapsis is the process of fusion of chromosome pairs at the start of meiosis. It takes place by crossing over the chromosome pairs. It takes place in the Prophase I of meiosis.

Complete answer:
Synapsis occurs between homologous chromosomes pairs during the zygotene stage of meiotic prophase. It is a meiotic-specific process. Homologous chromosomes are DNA fragments within a diploid organism of the same size one from each parental source. In meiosis, a single cell divides to produce four cells containing half the original amount of genetic information. This type of cell division occurs in sex cells – sperm in males, eggs in females.

Synapsis allows matching up of homologous pairs prior to their segregation. It allows chromosomal crossover and thus genetic material can be exchanged between the homologous chromosomes. The result of synapsis is a tetrad. During synapsis, the homologous pairs of sister chromatids line up together and connect. Synapsis refers to the even closer alignment of the homologs, usually via the parallel alignment of the meiotic chromosome cores that form a complex.

Option A: During cell division, the spindle fibre attaches to the centromere of chromosomes via kinetochore. Since synapsis does not occur between spindle fibres and centromere.
Therefore, this is the incorrect option.

Option B: Since synapsis does occur between two homologous chromosomes during the zygotene stage of meiotic prophase. Therefore, this is the correct option.

Option C: Gametes are haploid cells. Synapsis between the gametes does not occur. Therefore, this is the incorrect option.

Option D: During translation, the mRNA is embedded in the larger and smaller subunits of ribosomes. Since synapsis does not occur between mRNA and ribosomes. Therefore, this is the incorrect option.

Hence, the correct answer is option (B)

Note: The homologous chromosomes exchange the chromosomal segment after synapsis which causes genetic recombination. This recombination causes variation in the gene pool of the population. The result of synapsis is a tetrad.