Question

Which of the following statements is incorrect regarding the band region of the polytene chromosome?
A. Feulgen negative area
B. Absorb ultraviolet light at 2600 A˚
C. Chromonemata is tightly packed
D. Stain intensify with basic stain

Answer 1

Hint: Polytene chromosomes are chromosomes which contain thousands of DNA strands. These polytene chromosomes provide a high level of function in certain tissues such as salivary glands of insects.

Complete answer:
In insects, polytene chromosomes are commonly located in the salivary glands; they are also called "salivary gland chromosomes". The chromosome are of large size and this large size is due to the presence of many longitudinal strands known as chromonemata .
The chromosomal strands are formed after repeated division of the chromosome when the cytoplasmic division is not present.The polytene chromosome contains two types of bands 1.Dark bands 2. Interbands
 The dark bands are stained darkly and the inter bands are lightly stained with the nuclear stains. The dark bands have more DNA and less RNA. The interbands have more RNA and less DNA.
The bands of polytene chromosomes become enlarged at some of the times to form swellings that are called puffs. The formation of puffs is known as puffing. In the regions of puffs, the chromonemata uncoil and also it opens out to form many loops. The puffing is caused by the uncoiling of the individual chromomeres in a band. These puffs indicate the site of active genes where mRNA synthesis takes place.
Feulgen absorption spectra of polytene chromosome regions,these are differing in types of DNA composition and also of chromatin compactness, which were determined micro spectrophotometrically in squashed salivary glands of a species called as Rhynchosciara americana. The absorption curves exhibited a secondary maximum at their ascending branch after the chromatins were maximally depurinated.
Polytene chromosomes are euchromatic in nature and contain large amounts of DNA, small amounts of RNA and certain basic proteins. The chromosome is divided into dark bands (stain positive) and interbands (stain negative). The band is Feulgen positive or stained by Feulgen stain

So, the correct answer is 'Feulgen negative area'. Option A.

Note:
Polytene chromosomes are also found in dipteran flies; for example Drosophila, Chironomus and Rhynchosciara. They are present in another group of arthropods of the class Collembola, a protozoan group Ciliophora, mammalian trophoblasts and antipodal, and suspensor cells in plants.