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•Humans share 50% of their DNA with bananas.
•Cells can contain 6-9 feet of DNA. If all the DNA in your body
was put end to end, it would reach to the sun and back over 600
times.
•DNA in all humans is 99.9 percent identical. It is about one tenth
of one percent that makes us all unique, or about 3 million
nucleotides difference.
•DNA can store 25 gigabytes of information per inch and is the
most efficient storage system known to human. So, humans are
better than computers!!
•In an average meal, you eat approximately 55,000,000 cells or
between 63,000 to 93,000 miles of DNA.
•It would take a person typing 60 words per minute, eight hours a
day, around 50 years to type the human genome.
In the next
60 seconds
your body
will produce
enough new
DNA that
if it was
linked
together,
it would
stretch
100,000 km
Big Idea: Characteristics from parents are
passed to offspring in predictable ways.
Unit 2 Lesson 6 DNA Structure and Function
Essential Question: What is DNA?
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Unit 2 Lesson 6 DNA Structure and Function
Cracking the Code
What is DNA?
• The genetic material in cells is contained in a
molecule called deoxyribonucleic acid, or DNA.
• Scientists describe DNA as containing a code. A
code is a set of rules and symbols used to carry
information.
• To understand how DNA functions, you first need
to learn about the structure of the DNA molecule.
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Unit 2 Lesson 6 DNA Structure and Function
How was DNA discovered?
P = phosphate
S = Sugar
A = Adenine
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Unit 2 Lesson 6 DNA Structure and Function
How was DNA discovered?
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Unit 2 Lesson 6 DNA Structure and Function
How was DNA discovered?
• Many scientists from all over the world contributed
to our understanding of DNA.
• Some scientists discovered the chemicals that
make up DNA, and others learned how these
chemicals fit together.
• Still others determined the three-dimensional
structure of the DNA molecule.
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Unit 2 Lesson 6 DNA Structure and Function
Unraveling DNA
What does DNA look like?
• Experiments and imaging
techniques have helped scientists
to infer the shape of DNA.
• The structure of DNA is a twisted
ladder shape called a double
helix.
• The two sides of the ladder are
made of sugars and phosphate
groups.
• The rungs of the ladder are made
of pairs of bases.
Unit 2 Lesson 6 DNA Structure and Function
What does DNA look like?
• A base, a sugar, and a phosphate group make a
building block of DNA called a nucleotide.
• There are four different nucleotides in DNA.
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Unit 2 Lesson 6 DNA Structure and Function
What does DNA look like?
• The bases in nucleotides are
paired, or complementary.
• Adenine always pairs with thymine
(A-T).
• Cytosine always pairs with guanine
(C-G).
• The order of the nucleotides in
DNA is a code that carries
information.
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Unit 2 Lesson 6 DNA Structure and Function
What does DNA look like?
• Genes are segments of DNA that relate to a certain trait.
• The code in the nucleotide order has information about which
proteins the cells should build.
• The types of proteins that your body makes help determine
your traits.
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Unit 2 Lesson 6 DNA Structure and Function
Replication and Mutation
How are copies of DNA made?
• The cell makes copies of DNA molecules
through a process known as replication.
• During replication, the two strands of DNA
separate.
• The bases on each side of the molecule are
used as a pattern for a new strand.
• As bases on the original molecule are exposed,
complementary nucleotides are added.
• When replication is complete, there are two
identical DNA molecules.
1. UNZIPPING:
The DNA
molecule opens
up, separating
into two strands
2. COMPLEMENTARY
BASE PAIRING:
Nucleotides move
into position to bond
with the
complementary bases
on the DNA chain.
This process continues along
the primary chain until we have
2 IDENTICAL STRANDS of
DNA molecules (assuming
there have been no errors
made).
Unit 2 Lesson 6 DNA Structure and Function
p152
How are copies of DNA made?
Nucleotides
DNA
2 Strands
Identical
Molecules
Unit 2 Lesson 6 DNA Structure and Function
When are copies of DNA made?
• Before a cell divides, it copies its DNA so that each new
daughter cell has a complete set of instructions
• Our cells can replicate DNA in just a few hours, because
replication begins in many places along a DNA strand.
• Many groups of proteins are working to replicate your DNA
at the same time.
What are mutations?
DNA has the ability to mutate (change). This allows for
new characteristics and abilities to appear which may help
an individual to survive and reproduce (EVOLUTION).
Unit 2 Lesson 6 DNA Structure and Function
What are mutations?
• Mutations are changes in the number, type, or order of
bases on a piece of DNA.
• There are three main kinds of mutations:
• Deletion - a base is left out.
• Insertion - an extra base is added.
• The most common mutation – Substitution - when one
base replaces another.
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GENE MUTATIONS
Deletion: one nucleotide base is left out. All of the amino acids after
a deletion will be wrong, so SHAPE and FUNCTION of protein are altered.
Serious.
Insertion: one extra nucleotide base is added. This will also change
the entire amino acid sequence of the protein, so SHAPE and FUNCTION
of protein are altered. Serious.
Substitution: when single bases or short pieces are replaced with
one another.
Example: Sickle-Cell Anemia, only one nucleotide base is switched.
This causes only 1 amino acid to change, but it is an important one.
This type of mutation is usually not as serious as the 1st two. It just
depends on which amino acid is affected
Unit 2 Lesson 6 DNA Structure and Function
What are mutations?
• Which type of mutation is shown in each row?
Unit 2 Lesson 6 DNA Structure and Function
What are mutations?
Mutations can occur naturally, randomly or through
environmental factors.
Environmental mutagens include some
chemicals (food additives, pesticides, plastics) and
radiations (X-rays to UV light).
•Cells make proteins that
can fix errors in DNA, but
sometimes the mistake is
not corrected.
•The mistake then
becomes part of the
genetic code.
Unit 2 Lesson 6 DNA Structure and Function
What are mutations?
• A genetic disorder results from mutations that
harm the normal function of the cell.
• Some genetic disorders are inherited, or passed
on from parent to offspring.
• Other disorders result from mutations during a
person’s lifetime. Most cancers fall in this
category.
Unit 2 Lesson 6 DNA Structure and Function
Protein Factory
What is the role of DNA and RNA in
building proteins?
• Some of the information in the DNA is copied
to a separate molecule called RNA, or
ribonucleic acid.
• RNA is used to build proteins.
• Like DNA, RNA has a sugar-phosphate
backbone and the bases adenine (A),
guanine (G), and cytosine (C).
• Instead of thymine (T), RNA contains uracil
(U).
Unit 2 Lesson 6 DNA Structure and Function
Unit 2 Lesson 6 DNA Structure and Function
Protein Factory
What is the role of DNA and RNA in
building proteins?
• Three types of RNA have special roles
in making proteins.
• mRNA – Messenger RNA:
Provides instructions for building
proteins
• rRNA – Ribosomal RNA: Makes
up the ribosome
• tRNA – Transfer RNA: Transfers
amino acids to the ribosome
during translation
Unit 2 Lesson 6 DNA Structure and Function
What is the role of DNA and RNA in
building proteins?
• When a cell needs to make a
protein, it makes an RNA copy
of a section of the DNA. This
is called transcription.
• In transcription, DNA is used as
a template to make a
complementary strand of
messenger RNA (mRNA).
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Unit 2 Lesson 6 DNA Structure and Function
What is the role of DNA and RNA in
building proteins?
• The information in the mRNA is then used to build
proteins. This is called translation.
• In translation, the mRNA passes through a protein
assembly line within a ribosome.
Unit 2 Lesson 6 DNA Structure and Function
What is the role of DNA and RNA in building
proteins?
• A ribosome is a cell organelle
made of ribosomal RNA (rRNA)
and protein.
• As mRNA passes through, transfer
RNA (tRNA) delivers amino acids
to the ribosomes.
• The amino acids are joined
together to form a protein.
Process
Transcription
Translation
What molecules
are involved
DNA, mRNA
tRNA, ribosome
(rRNA), mRNA
Product
Complimentary
Strand
Protein