Chapter 9 of genetics
Robert J. Brooker, 7th edition
Chapter 9
9.1
molecular genetics - the study of DNA structure and function at a molecular level.
genetic material must meet four criteria:
1. The genetic material must contain the information necessary to construct an entire
organism.
2. During reproduction, the genetic material must be passed from parents to offspring,
transmission.
3. The genetic material must be copied, replication.
4. Within any species, a significant amount of phenotypic variability occurs, variation.
chromosomes are the carriers of genetic material. They contain DNA, RNA, and proteins.
Griffith's experiments indicated that genetic material could transform streptococcus.
Streptococcus is also known as the bacterium pneumococci. Certain strains of this secrete a
polysacharide capsule, whereas other strains do not. When streaked onto petri plates
containing a solid growth medium, capsule-secreting strains produce colonies with a smooth
morphology, whereas those strains unable to secrete a capsule produce colony with a rough
appearance. If the one with the smooth morphology enters an animal, the bacteria enter the
immune system and that can kill the animal. If the one with the rough appearance enters an
animal, the immune system of the animal will destroy the bacteria. In the experiment of
Griffith, a mouse got injected with rough morphology and with heat-killed smooth
morphology. Eventually the mouse died, and he found living smooth bacteria. He indicated
that the dead smooth bacteria were transforming the rough bacteria into smooth bacteria,
transformation.
Avery, MacLeod, and McCarty showed that DNA is the substance that transforms bacteria.
DNA, RNA, proteins, and carbohydrates are major constituents of living cells. To separate
these components and to determine if any of them was the genetic material, they used
established biochemical purification procedures and prepared extracts from smooth bacterial
strains that contained each type of these molecules. They discovered that only the one that
contained purified DNA from smooth bacteria, was able to convert rough bacteria into smooth
bacteria. If no DNA abstract was added, no smooth bacteria colonies were observed on the
petri plates. A DNA abstract is not 100% pure. This means that RNA and proteins also can be
the genetic material. To further verify that the DNA was responsible for the transformation,
they treated it with enzymes that digest DNA (DNase), RNA (RNase) and proteins (protease).
When the DNA abstract were treated with RNase and protease, they still converted type R
bacteria into type S. When it was treated with DNase, it lost its ability to convert type R
bacteria in type S bacteria. So, DNA is the genetic material. ("DNA is the transforming
principle").
Hershey and Chase provided evidence that DNA is the genetic material of T2 phage. T2 is a
virus that infects Escherichia Coli bacterial cells and is therefore known as a bacteriophage. A
phage only contains DNA and proteins. During infection, the phage coat remains attached on
the outside of the bacterium and does not enter the cell. Only the genetic material of the phage
Robert J. Brooker, 7th edition
Chapter 9
9.1
molecular genetics - the study of DNA structure and function at a molecular level.
genetic material must meet four criteria:
1. The genetic material must contain the information necessary to construct an entire
organism.
2. During reproduction, the genetic material must be passed from parents to offspring,
transmission.
3. The genetic material must be copied, replication.
4. Within any species, a significant amount of phenotypic variability occurs, variation.
chromosomes are the carriers of genetic material. They contain DNA, RNA, and proteins.
Griffith's experiments indicated that genetic material could transform streptococcus.
Streptococcus is also known as the bacterium pneumococci. Certain strains of this secrete a
polysacharide capsule, whereas other strains do not. When streaked onto petri plates
containing a solid growth medium, capsule-secreting strains produce colonies with a smooth
morphology, whereas those strains unable to secrete a capsule produce colony with a rough
appearance. If the one with the smooth morphology enters an animal, the bacteria enter the
immune system and that can kill the animal. If the one with the rough appearance enters an
animal, the immune system of the animal will destroy the bacteria. In the experiment of
Griffith, a mouse got injected with rough morphology and with heat-killed smooth
morphology. Eventually the mouse died, and he found living smooth bacteria. He indicated
that the dead smooth bacteria were transforming the rough bacteria into smooth bacteria,
transformation.
Avery, MacLeod, and McCarty showed that DNA is the substance that transforms bacteria.
DNA, RNA, proteins, and carbohydrates are major constituents of living cells. To separate
these components and to determine if any of them was the genetic material, they used
established biochemical purification procedures and prepared extracts from smooth bacterial
strains that contained each type of these molecules. They discovered that only the one that
contained purified DNA from smooth bacteria, was able to convert rough bacteria into smooth
bacteria. If no DNA abstract was added, no smooth bacteria colonies were observed on the
petri plates. A DNA abstract is not 100% pure. This means that RNA and proteins also can be
the genetic material. To further verify that the DNA was responsible for the transformation,
they treated it with enzymes that digest DNA (DNase), RNA (RNase) and proteins (protease).
When the DNA abstract were treated with RNase and protease, they still converted type R
bacteria into type S. When it was treated with DNase, it lost its ability to convert type R
bacteria in type S bacteria. So, DNA is the genetic material. ("DNA is the transforming
principle").
Hershey and Chase provided evidence that DNA is the genetic material of T2 phage. T2 is a
virus that infects Escherichia Coli bacterial cells and is therefore known as a bacteriophage. A
phage only contains DNA and proteins. During infection, the phage coat remains attached on
the outside of the bacterium and does not enter the cell. Only the genetic material of the phage
