Question

The structure of E. coli chromosomal DNA is
A. Double-stranded, right-handed and circular
B. Single-stranded, right-handed and circular
C. Double-stranded, left-handed and linear
D. Double-stranded, left-handed and circular

Answer 1

Hint: The DNA, deoxyribonucleic acid, is the genetic material. It is present in all types of organisms either prokaryotes or eukaryotes in the form of chromosomes. It acts as the messenger of genetic information generation over generation. It helps in the transfer of genetic information from parents to their offspring through gametes during reproduction.

Complete answer:
E. coli is a prokaryotic organism, which does not contain a nucleus and nuclear wall. Usually, the eukaryotic cell contains a well-developed nucleus surrounded by a nuclear wall. The DNA is found within the nucleus. It controls the overall function of a cell with the help of genetic information stored in DNA or chromosomes.

The DNA of E. coli is present in the cytoplasm due to lack of a well-developed nucleus. It contains a single chromosome located in the middle of the bacterial cell. It is a double-stranded molecule that is circular in structure. It is right-handed and highly supercoiled.

A double standard DNA molecule is made up of two strands of DNA, which are running in opposite or in antiparallel direction. They are held together with the help of hydrogen bonds between bases. The single-stranded DNA is made up of only one strand of DNA.

Hence, the correct answer is option (A), as the DNA of E. coli is double-stranded, right-handed and circular.

Note: The DNA of all types of cells (prokaryote or eukaryotes) duplicates itself by the process of DNA replication. The replicated DNA is divided equally into two daughter nuclei to be transferred in offspring. After the division of the nucleus, the cell cytoplasm is divided and produces two similar cells or offspring.