Q.Idiogram means:

An idiogram is a diagrammatic representation of the chromosomes (a schematic karyotype).

After chromosomes are photographed at metaphase and arranged in homologous pairs by size and centromere position (the karyotype), the standardised line-drawing of that arrangement is called an idiogram. It lets geneticists compare chromosome morphology and spot abnormalities. This is core NCERT Class 12 Biology genetics vocabulary.

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In human karyotyping, X belongs to group C and Y belongs to group G.

Human chromosomes are sorted into seven groups (A to G) by size and centromere position in the Denver system. The X chromosome is a medium-sized submetacentric chromosome and is grouped with group C (chromosomes 6-12). The Y chromosome is small and acrocentric and is placed in group G (with chromosomes 21 and 22).

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Human chromosomes 14 and 15 belong to classification Group D.

The standard (Denver) system groups the 23 pairs of human chromosomes (A-G) by size and centromere position; Group D comprises chromosomes 13, 14 and 15, which are acrocentric (centromere very near one end) and of medium length, often bearing satellite regions associated with nucleolar organiser regions. Group C, E and F correspond to different chromosome-number ranges and morphologies (e.g., Group …

Colchicine blocks mitotic spindle formation, arresting dividing cells at metaphase so their chromosomes can be studied in karyotyping.

Colchicine binds to tubulin and prevents microtubule (spindle-fibre) polymerisation, so cells cannot proceed past metaphase — the stage where chromosomes are maximally condensed and easiest to visualise and count, which is exactly what karyotyping (used to detect chromosomal disorders such as Down or Klinefelter syndrome) needs. Interferon is an antiviral signalling protein, endonucleases cut DN …