Cell Cycle and Chromosomes

In human beings, the presence of a Y-chromosome is required for the development of a male sex phenotype. In human beings, the presence of a Y-chromosome is required for the development of a male sex phenotype.

In Klinefelter’s syndrome, the chromosomal constitution of man is 22AA + XXY.Few men have XX karyotype and yet are males. This is a rare phenomenon due to translocation of a small segment of Y chromosome attached to an X chromosome and is inherited in concert with X. In Klinefelter’s syndrome, the chromosomal constitution of man is 22AA + XXY.Few men have XX karyotype and yet are males. This is a rare phenomenon due to translocation of a small segment of Y chromosome attached to an X chromosome and is inherited in concert with X.

Kinetin is a cytokinin that specifically promotes cytokinesis (cell division) by activating cell division-related genes. It does not directly cause karyokinesis (nuclear division), cell elongation (auxin function), or differentiation (complex process requiring multiple factors).

Translocation involves the exchange of chromosomal segments between two non-homologous chromosomes. Deletion, inversion, and duplication typically involve abnormalities within a single chromosome.

Protoplast fusion requires first removing the cell wall to isolate protoplasts (naked plant cells). Only after isolation can protoplasts be fused using techniques like PEG or electrofusion. Hybridization is the goal, not the first step, and somatic cell collection precedes protoplast isolation.

Statement (c) 'Linkage is usually complete' is false because crossing over between homologous chromosomes during meiosis can break linkage, making it incomplete. Statements (a), (b), and (d) are true: long pollen is dominant in Lathyrus, Drosophila has 4 chromosome pairs, and Mendel's law applies to genes on different chromosomes.

Meiosis I is referred to as a reductional division because it separates homologous chromosomes producing two haploid cells. During meiosis, crossing over takes place at pachytene stage. Kinetochore microtubules pull chromosomes towards opposite spindle poles in anaphase I.

Chromosomes are made of DNA and proteins (specifically histones). The DNA wraps around histone proteins to form the chromatin structure, which then condenses into chromosomes during cell division. Vitamins and lipids are not structural components of chromosomes. Option D is incorrect because it excludes DNA, which is the genetic material.

Genome stands for an entire set of genes in a cell or an organelle. Hence, this option is the correct answer.

Acridine orange is a nucleic acid selective fluorescent cationic dye useful for cell cycle determination. It is cell-permeable, and interacts with DNA and RNA by intercalation or electrostatic attractions respectively.

A locus is the specific fixed position on a chromosome where a particular gene is located. Chiasma refers to crossover points, while cistron is a functional unit of gene action.

Interchange of chromosome segments between non-homologous chromosomes is called translocation. Translocations can create reproductive barriers and lead to speciation because individuals with different translocation arrangements may have reduced fertility when mating. The other options describe chromosomal duplications, inversions, and deletions, which are less likely to cause species differentiation on their own.

Pisum sativum (garden pea), the plant Mendel used in his experiments, has a diploid chromosome number of 2n=14. This means somatic cells contain 14 chromosomes (7 pairs of homologous chromosomes). Option C (7) represents the haploid number (n) found in gametes, not somatic cells.

Pisum sativum (garden pea) has a diploid chromosome number of 2n=14, with n=7. This was Mendel's classic experimental organism for his inheritance studies. The haploid number is 7, so somatic cells contain 14 chromosomes arranged as 7 homologous pairs.