Video Transcript
Before it was established that DNA
was the genetic material, which biological molecule was commonly believed to carry
the genetic information?
This question asks about DNA and
early perceptions of genetic material. DNA was not always considered the
genetic material of cells, which passes on characteristics from parents to
offspring. As early as the 20th century,
scientists recognized that genetic material was passed from one generation to the
next. But they were unsure of how this
occurred and what molecule actually carried this information.
DNA was discovered in 1869 by a
scientist called Friedrich Miescher. He isolated the molecule from the
nuclei of immune cells and named it nuclein, but he didn’t know what function it
performed. In 1902 and 1903, two scientists
called Sutton and Boveri worked separately but reached similar conclusions. They put forth the chromosome
theory of inheritance. This theory stated that chromosomes
were responsible for carrying genetic material in the cells of living organisms.
Let’s quickly go over what
chromosomes are. Most of the cells in our body have
chromosomes in their nuclei. Chromosomes are linear structures
that contain tightly compacted DNA. This DNA is wound around special
proteins called histones. When organisms reproduce,
chromosomes are responsible for carrying genetic material from one generation to the
next.
What Sutton and Boveri didn’t
figure out was whether it was the DNA or the proteins in chromosomes that actually
carry this genetic material. At the time, most scientists
actually believed that the answer was proteins and not DNA. Over the course of the 20th
century, several groups of scientists performed experiments that eventually settled
the debate and convinced the world that DNA was the genetic material and not
proteins.
Now we can answer the question. Before it was established that DNA
was the genetic material, it was commonly believed that proteins carried the genetic
material.
