DNA
● What is deoxyribonucleic acid?
● What is the structure of DNA?
● Who discovered DNA?
● Why is DNA important?
● How does DNA replicate
during mitosis?
First, what do you already know?
What is deoxyribonucleic acid?
What is the structure of DNA?
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Deoxyribonucleic acid, or DNA, is the molecule that
carries all of our genes, the information that determines
what we look like.
It is found in the nucleus, but there is also DNA in
mitochondria.
On this page, write down what you think you know about
the questions on the previous slide.
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What is deoxyribonucleic acid?
What is the structure of DNA?
Who discovered DNA?
Why is DNA important?
How does DNA replicate during mitosis?
A unit of DNA is called a nucleotide. A nucleotide is made
of three parts
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A sugar
A phosphate
A base
There are 4 different bases
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Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
What is the structure of DNA?
What is the structure of DNA?
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● The sugar and phosphate make a
“backbone” for the DNA.
● The bases are connected in the
middle.
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Guanine and Cytosine pair together (G
and C)
Adenine and Thymine pair together (A
and T)
Who discovered DNA?
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Together, these parts then spiral into a “twisted ladder” shape that we
normally associate with DNA, called a double helix.
When DNA wraps around proteins called histones, which together,
make chromatin.
Chromatin condensed together makes the chromatids, which make
chromosomes.
Rosalind Franklin was an English scientist who used X-ray
diffraction to make images of the DNA. These images
helped reveal the main structure of DNA.
James Watson and Francis Crick used Franklin’s pictures
to figure out the “twisted ladder” structure of DNA. This
structure is called a “double helix”.
How does DNA replicate during
Mitosis?
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The double helix breaks in half, and proteins will make a
new strand for each strand.
Why is DNA important?
Why is DNA important?
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DNA’s most important function is to make proteins.
These proteins make up everything in our bodies!
Proteins are molecules with many, many, many jobs…
These can include telling when the cell needs to divide,
transport things within the cell, to tell the cell to start or
stop different jobs, etc.
DNA makes protein by making a
special copy of the DNA called
mRNA (messenger ribonucleic acid).
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mRNA, and RNA is slightly different from
DNA. In RNA, instead of having thymine,
there is uracil (U).
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The mRNA is delivered to ribosomes
outside the nucleus.
The ribosome “reads” the mRNA, and
makes proteins from those
instructions.