NEET BIOLOGY

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CELL STRUCTURES AND FUNCTION

CELL CYCLE

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Chromosomes are often made visible using Giemsa staining. This stain shows specific banding patterns for chromosomes, and helps scientists organize them under a microscope. Considering that chromosomes are the standard unit of organization for a cell’s DNA, during which phase of the cell cycle would chromosomes most likely be visible?
A
G2 Phase
B
Mitosis Phase
C
All Phases
D
S Phase
E
G2 Phase
Explanation: 

Detailed explanation-1: -Giemsa staining has been used for identifying individual human chromosomes. Giemsa-dark and-light bands generally are thought to correspond to GC-poor and GC-rich regions; however, several experiments showed that the correspondence is quite poor.

Detailed explanation-2: -A karyotype is the number and appearance of chromosomes, and includes their length, banding pattern, and centromere position. To obtain a view of an individual’s karyotype, cytologists photograph the chromosomes and then cut and paste each chromosome into a chart, or karyogram, also known as an ideogram (Figure 1).

Detailed explanation-3: -Chromosomes are visualized using Giemsa staining (G-banding). Light bands represent early replicating regions, rich in guanine and cytosine nucleotides. Dark bands represent late replicating regions, rich in adenine and thymine nucleotides.

Detailed explanation-4: -What causes a dark band on the chromosome? The Giemsa stain causes these dark bands to form on the chromosome. The specific pattern of Giemsa bands can help identify the chromosome. Additionally, G-banding can help identify specific chromosomal abnormalities and aberrations.

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