Cell Cycle and Chromosomes

The mixed lymphocyte reaction is used for typing MHC class II polymorphic variants.

The clinical presentation of short stature, webbed neck, and primary amenorrhea is characteristic of Turner syndrome, which is caused by a 45,XO karyotype.

An octomer that consists of four histone pairs complexed with DNA is called nucleosome.

Electron microscopic studies have shown that chromosomes consist of a number of substructures like centromere, secondary constriction, nuclear organizers, telomeres and satellites. Centromere is the joining point of two arms of a chromosome.

Synapsis is the pairing of homologous chromosomes during zygotene phase of meiosis. Homologous chromosomes are two chromosomes of the same type, size morphology and arrangement of gene loci. Out of the two homologous chromosomes present in an individual one is derived from the father and other from mother.

A zygote is formed by the fusion of a haploid sperm and a haploid egg. This fusion results in a diploid cell containing two sets of chromosomes.

Multiple alleles refer to the existence of more than two allelic forms of a gene at a specific locus within a population. While a single diploid individual can only carry two alleles, a population can harbor many variants due to different mutations.

Synapsis takes place during the zygotene stage of prophase one of meosis.

Chromosomes - In a cell which is not dividing, DNA is present as a part of chromatin material. Chromatin material is visible as entangled mass of thread like structures, But whenever the cell is about to divide, the chromatin material gets organized into chromosomes. Chromosomes are composed of DNA and protein. 

Reason: Nucleus contains chromosomes, which are visible as a rod shaped structures only when the cell is about to divide chromosomes composed of DNA and protein. DNA (Deoxyribose nucleic acid) helps in carrying information from parents to next generation. DNA is negatively charged and proteins associated with it are positively charged. The role of protein is to pack DNA. Vitamins or lipids cannot be used to pack DNA.Therefore (B) is correct answer 

Amniocentesis involves analyzing amniotic fluid to detect chromosomal abnormalities, such as Turner's syndrome and Klinefelter's syndrome, and it can also reveal the sex of the fetus.

Karyotaxonomy is a branch of taxonomy that uses the number, size, and structure of chromosomes to classify organisms and determine their evolutionary relationships.

Meiosis is a reduction division. If the mother cell has 40 chromosomes, the resulting microspores will have half that number, which is 20.

 CELL CYCLE SEQUENCE IS M,G1,S,G2.

  Structure of chromosome is studied at Metaphase stage.