Download DNA and RNA

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Biology
• So far in the course we have discussed the many
aspects of the cell. What is the control center of the
cell? What is present in the nucleus of the cell? What is
a chromosome made up of? DNA is the cells genetic
A gene is a
stretch of DNA that
codes for a specific
protein. The proteins produced by the cell make
material. What is a gene?
life as we know it possible.
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Biology
DNA, which stands for
Deoxyribonucleic Acid, is one of the major
•
organic molecules that we discussed along with
The
structure of a DNA molecule is
called a double helix. The best way to
carbohydrates, fats, and proteins.
visualize a double helix is to think of a ladder that
has been twisted.
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Biology
The long strands of DNA are made up of
The
building blocks are called
Nucleotides. Nucleotides are
made up of three different
substances: Sugar, Phosphate,
and Bases. The sugar and phosphates represent
monomers, or building blocks.
the sides of the ladder and the bases represent the
rungs of the ladder.
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Biology
There
are four
bases
present
in DNA:
Adenine,
Guanine,
Thymine,
and
Cytosine.
The base pairs have specific
matching patterns. Adenine (A)
always pairs with (T) A-T. Guanine
(G) always pairs with Cytosine (C)
G-C. This base pairing is called complementary.
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Biology
The base pairs from each strand form a bond between each other
creating the double helix.
•Form the complementary strand to this section of DNA.
T T A G C C G C T T T G T C T G A A G C C A T
Chargaff’s Rule:
In double stranded DNA the
number adenines equals the
number of thymine’s (A equals
T), and the number of guanines
equals the number of cytosine’s
(G equals C)
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Biology
DNA Replication
When cells replicate (divide)
they need to make copies of the
genetic information so that the
new cells can function properly.
•
This process of
replication is conducted
by an enzyme called DNA
polymerase. Another enzyme
(helicase) unzips the double helix creating a
replication fork.
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Biology
•Notice that two new
molecules of DNA are
being produced, this
occurs simultaneously.
•The complementary
base pairing is
conducted by the
DNA polymerase,
which is reading and
bringing in the
correct base pairs to
build a new strand.
• Enzymes
(helicase)
which are
proteins
responsible for
the unzipping
of the original
strand.
• Each strand of the old DNA serves as a template for new strand
production. For example, a strand that has the bases TACGTT
produces a strand with the complementary bases ATGCAA.
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Biology
RNA and Protein Synthesis
• As we have already learned DNA is the blueprint to produce all
of the proteins we need to be a functioning organism. Where
does the production of proteins occur?
The production of proteins occurs in cytoplasm and more
The DNA
molecule is too large to
leave the nucleus of the
cell, therefore there needs to be a
specifically on the ribosomes.
system of relaying the genes to the
cytoplasm. RNA, or ribonucleic
acids, carry out the process of
making proteins.
The Structure of RNA
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Biology
RNA like DNA consists of a long chain of nucleotides. Each
nucleotide is made up of a sugar, phosphate, and base. There are
three main differences between RNA and DNA.
1.
The sugar in RNA is ribose
instead of deoxyribose.
2. RNA is a single strand.
3. RNA contains Uracil in place
of Thymine.
Types of RNA
• The assembly of amino acids into proteins is controlled by RNA.
There are three different types of RNA
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Biology
molecules and their main function is protein
synthesis.
1.
Messenger RNA (mRNA): These
RNA molecules are copies of the
gene that move from the nucleus to
the cytoplasm. They serve as “messengers”
from DNA to the rest of the cell.
2. Ribosomal RNA (rRNA): Proteins are
constructed on the ribosome which is made of
rRNA.
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Biology
3. Transfer RNA
(tRNA): When the
protein is being built
this third type of
molecule brings the
amino acids to the
ribosome.
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Biology
Transcription
• Transcription is the
process in which a
messenger RNA
molecule is made by
copying a segment of
the DNA (gene).
Transcription requires
an enzyme known as
RNA polymerase.
•RNA polymerase uses one
strand of DNA as a template
from which nucleotides are
assembled into a strand of
mRNA. The mRNA is small
enough to leave the nucleus.
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Biology
RNA Editing
• Before the RNA can leave the nucleus there is some
modification that takes place. RNA/DNA is made up of two
types of sequences, introns and exons. The introns are
sequences of RNA that are non coding, these stretches of
RNA are cut out of the molecule. The exons are the areas of
the gene that are responsible for the expression of a gene.
The diagram above displays the process of RNA editing. The
introns are cut out and removed to form the mRNA that is a
pure coding strand.
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Biology
•Now that a messenger RNA strand has been produced
(transcription) the information can be moved to the ribosome
in the cytoplasm. This whole process is geared towards
producing proteins; let’s review the structure of a protein.
•Proteins are one of the four major organic molecules in the
The
protein is a polymer which is made up of
individual building blocks called amino acids.
human body. They have multiple jobs in the body.
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Biology
The
arrangement of the bases in mRNA determines
the arrangement of the amino acids. The
There are a total of 20 different amino acids.
The
code for an amino acid is only
three bases long (this is called
a Codon); for example, let’s look at the following
“language” of mRNA is called the genetic code.
mRNA sequence.
UCGCACGGU
This sequence would be read three bases at a time from left
to right.
UCG-CAC-GGU
The codons represent the different amino acids:
UCG-CAC-GGU
Serine-Histidine-Glycine
Because there are four different bases, there are 64 possible
three-base codons (4x4x4=64).
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Biology
•Notice that many of the codons represent the same amino
acid. There are also codons that determine when the
translation stops.
Translation
•The decoding of mRNA messages into a protein is
known as translation. During translation, the cell uses
information from the mRNA to produce proteins. This
production of protein occurs on the ribosomes.
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Biology
•Translation begins when an mRNA molecule in the cytoplasm
attaches to a ribosome.
•As each codon of the mRNA molecule moves through the
ribosome, the proper amino acid is brought into the ribosome
and attached to the growing protein chain.
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Biology
The amino acid is brought
to the ribosome by transfer
One
end of the
tRNA carries
the amino acid
and the other
end has three
bases that
read the
mRNA that are
called
anticodon.
RNA (tRNA).
• Like an assembly line worker who attaches one part to
another the ribosome forms the bonds between the amino
acids. The protein chain continues to grow until the ribosome
reaches the stop codon. When the ribosome reaches the stop
codon, it releases the newly formed protein and the mRNA
molecule, completing the process of translation.
Name ________________________________________ Date ______________ Block__
Biology