Question

Thinking about the number of different cell types on the planet has changed over the years. We now recognize

A.   2 basic cell types: prokaryotes and eukaryotes

B.   3 basic cell types: bacteria, archaea and eukaryotes

C.   2 basic cell types: that have a nucleus and cells that have an internal membrane system

D.   3 basic cell types: cells with a nucleus, cells with endoplasmic reticulum, and cells with mitochondria

E.   only 1 type of cells: cells with DNA as genetic material

Answer 1

Initiallly cells are divided into two main classes based on whether they contain nucleus that is prokaryotic cells and eukaryotic cells which have the nucleus in which the genetic material is separated from cytoplasm. Due to absence of nucleus their genomes are less complex than eukaryotic because they do not contain cytoplasmic organelles. So this indicates that all present day cells are produced from single primordial ancestor.

After that RNA has been initial genetic system and early stage of chemical evolution and this period known as RNA world. Then these RNA and amino acids evolved into present day genetic code and DNA which is at the end replaced RNA as genetic material.

Hence option (E) is correct.