BIO 2 GO!
NUCLEIC ACIDS
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Nucleic Acids are organic molecules that carry the genetic information
for every living organism. All living things contain nucleic acids. The
DNA and RNA are responsible for providing a plan for the construction
of new cells and organisms. Failures in this system lead to mutation and
sometimes death.
NUCLEIC ACIDS
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At the end of this unit of study, you should be able to do the following:
1. Describe and explain the basic structure of DNA and RNA
2. Describe and explain the function of DNA and RNA
4. Describe and explain the process of DNA replication
6. Describe and explain the basic structure of a nucleotide
7. Describe and explain the function(s) of a nucleotide
8. Be able to use the following terms correctly:
DNA
single strand
RNA
DNA replication
nucleotide
genetic information
double helix
sugar, phosphate, nitrogen bases
Nucleic Acids
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Let’s keep this simple. When we talk about nucleic acids we are talking
about either DNA or RNA. DNA is the most important. DNA is an organic
molecule that contains the genetic information, or building plan, for all living
things. DNA tells the cell how to build whatever it needs. DNA also makes
up the genes for all living organisms, including humans. Genes and protein are
what make up the chromosomes for all living things. The chromosomes carry
all of the genes. They are located in the nucleus of every living cell.
REMEMBER THIS !!!
DNA and RNA are the nucleic acids.
Interesting Scientific Fact: A human being has about 100,000 genes.
Function of DNA, RNA
DNA has 1 important function. Its job is to convey the correct genetic
information from 1 generation to the next - from parent to child.
RNA has several functions, 2 of which are the following: To copy the
DNA of a cell and transport the DNA copy to the ribosomes so they can
make new protein for use by the cell.
Question 1. What are the two types of nucleic acids?
Question 2. What is the function of DNA?
Question 3. What are the 2 functions of RNA?
DNA Explained
DNA contains the genetic information for all living things - including
you. In other words, DNA determines what all living things will look like.
That is called the genetic information for an organism. Genetic information
is the plan that determines what all living things will look like and what they
can do.
DNA is the genetic information and is responsible for correctly
transferring the plan from one generation to the next. In your case, for
instance, your DNA determines your height, hair color and eye color.
DNA also determines whether a living organism will grow into a tree, a
turtle, or you. Living things receive their DNA from their parents. You
inherited your DNA from your mother and father.
One half came from your mother and one half came from your father.
That is why children often look like their parents. That is why all oak trees
look alike. That is why all rockfish look alike.
Interesting Scientific Fact: Sometimes the genetic information is not
transferred correctly. As a result, the offspring may inherit something
different from that of the parents. This process is called a mutation.
Whenever the offspring do not correctly inherit the DNA plan from a
parent, a mutation has occurred. Mutations are quite frequent. Normally,
they are unnoticed by the organism. However, sometimes they produce
abnormalities in the offspring. In humans such abnormalities include sickle
cell anemia, cystic fibrosis, and Mongoloidism. Sometimes the mutations are
even fatal.
Example of a mutation
Line 1 is a normal strand of DNA.
Line 2 has a piece of DNA being cut out of it.
Line 3 is the new piece of DNA that is now different from the
original (Line 1) so it is called a mutation.
Interesting Scientific Fact: A number of things in the environment seem to
cause mutations in humans. Some of the better known are: ultraviolet light,
certain controlled substances (drugs), and radiation.
REMEMBER THIS !!!
Genetic information is the plan that determines what a living thing will
look like. DNA is the genetic information. DNA is found in the nucleus
of all living cells in every living organism.
Interesting Scientific Fact: Werewolves do not exist. However, there is a
gene in humans that if inherited from both parents, causes a lot of hair to
grow on the upper body and even cover the face, ears, nose, cheeks,
forehead, even eyelids-much like a picture of a werewolf. This gene does not
affect personality. In fact, there are pictures of a family in Europe that
passed this gene on from generation to generation. They were regarded
with great admiration by the rulers at that time.
Question 4. Describe and explain how genetic information and DNA are
related.
Question 5. Explain how genetic information is transferred from parent to
offspring in all living things.
Question 6. What determines whether a living organism will grow into a
human or a flower?
RNA Explained
One of the things that RNA does is to make a copy of the DNA and take
it to a place in the cell (the ribosome) where it can be “read” to make protein
for use by the cell. As you have already learned, protein is widely used to
make all living things. For instance, proteins make up muscles, tissues and
organs. The RNA is responsible for copying the DNA correctly and having
another part of the cell create the new protein.
It is important to know that both DNA and RNA look similar because
they are made from nucleotides. We will discuss nucleotides in the next
section.
REMEMBER THIS !!!
One function of RNA is to copy DNA and then have another part of
the cell use the copy to make protein.
Nucleotides Explained
Nucleotides are the building blocks that make up both DNA and RNA.
Nucleotides contain 3 parts: sugar, phosphate, and a nitrogen base. You will
need to remember the three parts of a nucleotide. Although the sugar and
phosphate is the same in all nucleotides, the nitrogen bases may vary. That
is why there is more than 1 type of nucleotide.
Nucleotides have a phosphate group, a
sugar (deoxyribose sugar) and a
nitrogen base (the Adenine).
Interesting Scientific Fact:
bases in every adult human.
There are about 3,000,000,000 nitrogen
REMEMBER THIS !!!
All nucleotides are made from 3 things: a sugar, a phosphate, and a
nitrogen base.
REMEMBER THIS !!!
Both DNA and RNA are composed on nucleotides.
Question 7. How would you describe and explain the function of RNA?
Question 8. What is the importance of nucleotides?
Question 9. What are the three parts of a nucleotide?
Question 10. If you were going to build a single strand of RNA, what would
you need to use?
DNA Replication – putting it all together
The way DNA is made is an interesting process. First it is important to
know a little about the structure of a DNA molecule. You already know that
DNA is made from nucleotides. You probably do not know this next part.
In every molecule of DNA there are two strands of DNA, much like a
ladder. Now imagine twisting the ladder so that it looks more like a circular
staircase. This is called a double helix. DNA is a double helix. It would look
like a twisted ladder. This is important to remember.
In the first step of DNA replication the double helix is divided so that
DNA is separated into 2 separate strands. Imagine cutting the steps of a
ladder top to bottom so that the ladder splits into two identical pieces.
That is what happens to the DNA.
When the DNA strands are separated, new nucleotides come in to
replace the DNA strand that has been separated. Because of this, each
DNA strand gets what it needs to become a double helix again. As a result,
there are now 2 double helix (helices) instead of just 1. The DNA has
replicated itself!
REMEMBER THIS !!!
DNA divides, separates, and attracts new nucleotides to replace the
strand that split away.
Interesting Scientific Fact: DNA and RNA work together to make
protein. Protein, as you recall, is the type of molecule of which most living
things are made. Here is how it works. The first part of the process is
similar to DNA replication – the DNA double helix splits and separates.
After the DNA has separated into 2 strands, the RNA comes in and makes a
copy of the DNA. However, RNA is a single strand. Therefore it can only
copy one side of the DNA at a time. In other words, it copies only one
side of the ladder.
The RNA then takes copies of the DNA to a particular place in the cell,
called ribosomes, where the RNA tells the ribosomes how to arrange the
amino acids in order to make the correct protein for the construction or
repair of the living thing. That is how protein is made. You will need to
know this process in a later chapter.
REMEMBER THIS !!!
DNA is a double helix, RNA is a single strand.
Question 11. How would you describe and explain a double helix to someone?
Question 12. Explain the process where RNA helps to make proteins.
Similarities and Differences in DNA, RNA
Similarities
1. Both DNA and RNA are made from nucleotides
2. Both are found in every living cell
Differences
1. DNA is a double helix, RNA is a single strand
2. DNA is the genetic information; RNA makes copies of the DNA code
Summary
Nucleic acids are molecules in a cell that store a code, also called
the genetic information, for that cell. This code helps the cell arrange its
amino acids together in the correct order to make its proteins. The two
types of nucleic acids are DNA (deoxyribonucleic acid) and RNA
(ribonucleic acid). DNA and RNA molecules are made of nucleotides.
Nucleotides are linked together to make DNA and RNA like amino acids are
linked together to make proteins.
A nucleotide is made of three parts, a sugar, a phosphate group,
and a nitrogen base. In DNA, there are four different types of nitrogen
bases. DNA is two strands of nucleotides, hooked together and twisted into
a ladder shape called a double helix.
RNA is a nucleic acid that is a single strand of nucleotides. Its
job is to copy the code in the DNA and to use the copy to make a cell’s
proteins. DNA’s role is to store genetic information, or code, in the nucleus
of a cell. It also allows parents to pass on their genetic information to their
offspring.
James Watson and Frances Crick (at left)
discovered the structure of DNA in 1953,
building of the work of other scientists
Chargraff, Franklin, and Wilkins.
Matching
_____ 1. single strand
a. molecules that store a code
_____ 2. amino acids
b. RNA ( ribonucleic acid )
DNA ( deoxyribonucleic acid )
_____ 3. nucleic acids
c. copies the DNA code
_____ 4. DNA
d. building blocks of DNA and RNA
_____ 5. RNA
e. shape of an RNA molecule
_____ 6. nucleotides
f. building blocks of a protein
_____ 7. double helix
g. shape of a DNA molecule
True or False
_____1. The code in DNA helps the cell arrange its amino acids together in
the correct order to make its proteins.
_____ 2. The two types of nucleic acids are DNA and RNA.
_____ 3. Amino acids are the building blocks of nucleic acids.
_____ 4. Nucleotides are the building blocks of nucleic acids.
_____ 5. A nucleotide is made of a sugar, a phosphate, and a nitrogen base.
_____ 6. There are several different nitrogen bases.
_____ 7. Carbohydrates are a major component of nucleic acids
_____ 8. RNA is made of two strands of nucleotides.
_____ 9. A double helix is like a twisted ladder.
_____ 10. The shape of DNA is a double helix.
_____ 11. The job of RNA is to store genetic information in the nucleus of
a cell.
_____ 12. A function of DNA is to allow parents to pass on their genetic
information to their offspring.
_____ 13. The function of RNA is to help the cells use the code in the DNA
to make new proteins for the cell.
Completing Sentences
nucleic acids
nucleotides
nitrogen base
DNA
sugar
double helix
RNA
phosphate
single strand
1. The two types of nucleic acids are _____________ and
_______________.
2. __________________________ are the building blocks of nucleic
acids.
3. Each nucleotide is made of a __________________, a
_________________________and a ________________________.
4. A double helix is used to describe the shape of
____________________________.
5. A single strand is used to describe the shape of
___________________________.
6. The shape of a DNA molecule is called a
____________________________.
7. __________________________ are molecules that help the cell make
its proteins correctly.
8. RNA and DNA are classified as ____________________________.
9. The shape of an RNA molecule is described as ___________________.
Answer the following.
1. What are the two types of nucleic acids?
2. What are the building blocks of nucleic acids?
3. What are the three parts of a nucleotide?
4. What is the shape of a DNA molecule?
5. How are RNA and DNA different?