Final answer:
Exposure of polytene chromosomes to thermal stress can lead to denaturation of DNA, chromosomal abnormalities, and disruption of proteins involved in chromosome structure.
Step-by-step explanation:
If the polytene chromosomes are exposed to thermal stress, they may undergo various changes. One possible effect is the denaturation of DNA, which occurs when high temperatures cause the hydrogen bonds between the bases to break. This can lead to chromosomal abnormalities and impact the proper functioning of the cell. Additionally, thermal stress can also result in the disruption of proteins involved in chromosome structure, such as condensins, which could affect the condensation and segregation of chromosomes during cell division.