Cell Cycle and Chromosomes

Roots from onion can be easily grown in the lab.

The correct option is 4.

Meiosis results into 4 daughter cells. It is irrespective of the number of chromosomes.

The synaptonemal complex forms during Meiosis I (specifically zygotene sub-stage of prophase I) to facilitate synapsis between homologous chromosomes. It does not form in mitosis or meiosis II.

Some cells split via budding (for example baker yeast), resulting in a 'mother' and 'daughter' cell. The offspring organism is smaller than the parent. Budding is also known on a multicellular level; an animal example is the hydra which reproduces by budding. The buds grow into fully matured individuals which eventually break away from the parent organism.

inactive x chromosome

haploid DNA content of an organism

Down's syndrome is a trisomic condition on the 21st chromosome which is the result of non disjunction, i.e. failure of synapsed homologous chromosomes to separate during anaphase-I of meiosis. 

The homologous chromosomes pair up and form synaptonemal complex during this phase.

Aneuploidy refers to a condition where the chromosome number is not an exact multiple of the haploid set, involving the loss or gain of individual chromosomes. Polyploidy involves the addition of entire sets of chromosomes, while polyteny refers to giant chromosomes formed by repeated replication without division.

Translocation is a chromosomal abnormality where a segment from one chromosome breaks off and attaches to a non-homologous chromosome. This differs from inversion, where a segment is reversed within the same chromosome, or deletion, where a segment is lost.

An increase in the number of X chromosomes (X complement), such as in Klinefelter syndrome (XXY) or Triple X syndrome (XXX), is often associated with cognitive deficits and mental retardation. While Y chromosome abnormalities exist, the X complement has a more pronounced effect on neurodevelopmental outcomes.

Edward's syndrome is caused by trisomy 18, which is the presence of an extra 18th autosomal chromosome. Down's syndrome involves chromosome 21, and Patau's syndrome (misspelled as Paton's in the options) involves chromosome 13.

Endomitosis is a process where chromosomes replicate within a cell without the subsequent division of the nucleus or the cell itself. This leads to endopolyploidy, increasing the number of chromosome sets within a single nucleus.

Pollen grains are haploid (n), so if their chromosome number is X, then n = X. In angiosperms, the endosperm is formed by triple fusion (one male gamete plus two polar nuclei), making it triploid (3n). Therefore, the number of chromosomes in the endosperm will be 3X.