DDT stands for dichloro-diphenyl-trichloroethane. The first kind of synthetic/artificial insecticides came into use in the 1940s. The earlier usage of DDT include: a) Killing of malarial vectors, b) Combatting Typhus and other insect borne human diseases, c) As a pest control in crops d) as a pest control in garden, live stock production and even at homes.
The negative impact of DDT could be felt for the first time when the pests that were earlier killed by use of DDT have now become pesticides resistant. In the 1950s in USA, the regulatory measures were adopted to reduce the usage of DDTs as its effects as a pesticides were no more long significant and also it was creating detrimental physical and psychological impacts on the human and environment.
It was in 1972 that the U.S. Environmental Protection Agency cancelled the order for banning the usage of DDT based on the adverse impact it produced on the environment, human and other life forms. Since then continuous studies are being conducted to analyse the impact of DDTs. In some later years it was established that DDT is the cause of producing tumors in liver.
Some of the common negative impacts produced by DDT as per the U.S. Department of Agriculture :
a) The non destructive nature – DDT can not be destroyed and thus it remains persistent in the atmosphere
b) It attacks the tissues of living organisms especially the animals and humans ( fatty tissue)
c) It can penetrate the atmosphere to deeper extent.
Now as per the current stuation, The use of DDT is controlled and other alternatives of pest control organisms is being deduced. As per the treaty of Stockholm Convention on POPs (Persistent organic pollutants) , usage of DDT for malarial control is justified but it puts a restrictive use of DDT as pesticides in other areas.
Answer:
Since cells are utilized at a point or the other in the organism life we can say the general concept of life-is-cellular holds and abandon the cell membrane partitions notion
Explanation:
where the metabolic processes occur that keep the organism alive is the cellular level of an organism (the general concept of life-is-cellular)
Study a chemical process and a chemical transformation.
Answer: Option E
Maintaining very long telomeres promotes cancer cell formation.
Explanation:
Telomere refers to either of the sequences of DNA at each end of a eukaryotic chromosome.
Usually, in eukaryote chromosome replication, telomeres are not replicated.
Hence, they are usually lost resulting in the shortening of the telomere ends after repeated cycle of cell division. This also leads to cell aging and stoppage of cell division.
The shortening of telomere combined with stoppage of cell division, and cell aging initiation prevent CANCER, which thrives on lengthy telomeres
Answer
When a eukaryotic cell is not undergoing mitosis, the DNA and its associated proteins appear as a visible network of dark fibers called the Chromatin.
Definition
Chromatin is a thread like structure that can be seen inside nucleus before cell division. It is a complex of DNA and histone proteins.
Forms of chromatin
Chromatin exist in two forms, that is
a. Euchromatin
It is less condensed and can be easily transcribed.
b. Heterochromatin
It is highly condensed and not transcribed as easy.
Organization of chromatin
Microscopy has shown the appearance of chromatin as beads on a string. The beads are called nucleosomes.
Nucleosome
Each nucleosome is composed of DNA wrapped around eight histone proteins. The nucleosome is then wrapped into a 30nm spiral called solenoid.
