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The Genetic Material
DNA/RNA Notes
Bodies  Cells  DNA
 Bodies are made up of cells
 All cells run on a set of
instructions spelled out in DNA
1. DNA:
What is the role of DNA in heredity?

DNA stores genetic information. It tells our eyes
which color to be, it tells our cells which proteins
to make, and when to make them.

DNA copies genetic information. Before a cell
divides, it must copy its DNA

DNA transmits genetic information from one
generation to the next.
*** a gene is a part of the DNA that codes for one
specific protein.
The Structure of DNA:
Made of 100s of repeating
units called nucleotides.
Nucleotides include:
a. Deoxyribose (a sugar)
b. A Phosphate Group
c. One of four possible
Nitrogenous Bases…
The Four Nucleotides in DNA


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1.
2.
3.
4.
Adenine
Thymine
Guanine
Cytosine
Adenine Guanine
Thymine
Cytosine
Phosphate group
Deoxyribose
Nucleotide Use


Like letters in the alphabet, these four
nitrogenous bases are strung together
in many different arrangements that
code for the genetic information.
DNA’s structure is what allows it to code
for, copy, and transmit the information
need by our cells to function.
1953 | 1962
2. Structure of DNA

James Watson and
Francis Crick worked
out the threedimensional structure
of DNA, based on
work by Rosalind
Franklin and Maurice
Wilkens
Wilkins
Rosalind Franklin (1920-1958)
Her picture of DNA,
taken by x-ray
diffraction, helped
Watson and Crick
tease out the double
helix structure of the
DNA molecule
2. The Structure of DNA
The Double Helix:
 Adenine always bonds to Thymine
A-T
 Cytosine always bonds to Guanine
C-G
-This attraction (called Base Pairing) is
caused by hydrogen bonds between the
bases.
Twisted Ladder



The double helix looks
like a twisted ladder.
The rungs of the ladder
are the nitrogenous
bases (A, T, C, G)
The sides of the ladder
are the Phosphate and
the sugar (sometimes
called the backbone of
the molecule)
More on the double helix

Two separate and
opposite (called
anti-parallel)
strands wrap
around each other
Sugarto form a stable phosphate
twisting molecule backbone
called a double helix
Nucleotide
Hydrogen
bonds
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Let’s try building a DNA
molecule

Build a DNA
Molecule
New
Strand
Original
Strand
DNA
Polymerase
3. DNA Replication
Before a cell divides, it duplicates its DNA.
This process is called replication and it is
controlled by a series of enzymes.


1. Each strand of DNA has all the information to
create the other strand by “base pairing.”
2. DNA strands are Complementary (or
opposites) if the two strands are separated, they
can recreate their own complementary strand.
Process of DNA Replication:


1. Enzymes “unzip” a molecule of DNA
by breaking the hydrogen bonds
between base pairs. (DNA Helicase)
2. The two strands unwind and each
becomes a template for the other
strand.
Process of DNA Replication:


3. Free nucleotides in the nucleus
attach to each of the strands, forming
two identical sets of DNA!
4. DNA Polymerase- one of the
enzymes involved in replication, adds
the new bases (nucleotides) and proofreads each strand so there are very few
mistakes.
Let’s try Worksheet #3
A Science Odyssey: You Try It: DNA
Workshop
4. RNA


The main role of RNA is to aid in Protein
Synthesis
RNA is similar to DNA in that both are
made of nucleotides
What is RNA?
RNA is different than DNA:
Sugar backbone in RNA is Ribose (not
Deoxyribose)
 RNA is single stranded while DNA is double
stranded
 RNA contains Uracil in place of Thymine.
(U in place of T)
 DNA always stays in the nucleus, while RNA
can be found in the nucleus and cytoplasm.

Types of RNA
Messenger RNA (mRNA)
 The role of mRNA is to carry instructions for
making proteins from DNA to Ribosomes.
Ribosomal RNA (rRNA)
 One of the building blocks of Ribosomes
Transfer RNA (tRNA)
 Transfers amino acids to ribosomes in the
specific order that mRNA states in order to
make a specific protein.
Process of Protein Synthesis

Cells store a huge amount of coded information in
their genes. Much of this information is used to make
1000s of proteins that each cell requires for its
functions and the structures it contains. The cell’s
proteins are made at the ribosomes according to the
directions stored in the cell’s DNA code.
RNA carries the DNA code from the Nucleus to
the ribosomes in the cytoplasm.
 Protein synthesis is divided into two parts:


Transcription
Translation
5. Transcription-
before we can make a
protein, we need a copy of the code that can leave the
nucleus


Transcription is the process of making
strands of RNA from DNA.
Transcription requires the enzyme
RNA Polymerase.
A Look at Transcription
•Synthesis of a protein starts in the nucleus
•DNA molecule unzips (just like in DNA replication)
•RNA polymerase adds nucleotides in groups of three
• Adenine pairs with Uracil instead of Thymine
• Cytosine pairs to Guanine
Let’s try it
A Science Odyssey: You Try It: DNA
Workshop
DNA Transcription - YouTube
6. The Genetic Code &
Protein Synthesis
1. Proteins are made by joining long chains of
amino acids together to form polypeptides.
a. There are a total of 20 different
amino acids.
b. Different proteins are made by
different combinations and numbers
of these amino acids.
c. These amino acids are assembled
using the Genetic code. Cells store this
code in their DNA.
More on Protein Synthesis
RNA contains 4 different bases A, U, C,
and G. The order of these subunits is
the Genetic code.
a. The genetic code is read three letters
at a time, this is called a “Codon.”
b. Each codon instructs for one amino
acid to be built into a chain.
Example:
 RNA: UCGCACGGU is read as a series
of three codons:
UCG-CAC-GGU
 These different codons represent three
different amino acids.
UCG
CAC
GGU
Serine - Histadine - Glycine

The codons
for the
specific amino
acids are
listed using
this table:
7. Translation

The process
of a cell using
mRNA and
ribosomes to
make proteins
is translation
How translation takes place
How translation takes place

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mRNA carries the codons to the ribosome.
A tRNA that has a complementary codon
binds to the mRNA by base pairing.
The tRNA carries on its other end an amino
acid that corresponds to the codon.
As each tRNA binds to the mRNA, the amino
acids bond together to form polypeptide
chains.
A Science Odyssey: You Try It: DNA
Workshop
Putting it all together

DNA
 RNA
Transcription

Proteins
 Traits
Translation
•This simple phrase links all the important
genetic components together and is the basis
for the science of molecular biology
8. Mutations

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Mutations are changes in the
nucleotide sequence in a DNA
molecule that can be inherited.
Can have no affect at all
Or they can change the amino acid
being inserted into a protein and make
that protein nonfunctional.
Mutations can benefit an organism or
harm it.
What is Different?
DNA sequence 1- GCC-ATC-CGC-ATT-AGA
DNA sequence 2- GCC-ATC-CAC-ATT-AGA
Mutations –gene mutations


The most common type of mutation is a
Point Mutation that occur at a single point
in the DNA sequence.
These generally occur during replication of
the DNA.
Examples of Point mutations
Substitution:
CTT - CAT in the DNA
The mRNA switches from
GAA to GUA
instead of glutamic acid, valine is added to the
polypeptide chain.
Sickle cell disease affects the shape of red blood cells.
It is the result of a point mutation.
Evolution: Library: A Mutation Story
Point Mutations

Types of Point mutations are:
 Substitutions- one base is changed to
a different base
 Insertions or deletions- one base is
inserted or deleted from the DNA
sequence
Insertions/deletions

Insertions and deletions can cause a shift in the
reading frame of the mRNA codons during
translation.
AUG – GCT – ATT - CGA
AUG – GAC – TAT – TCG - A
This will change the amino acids being inserted from
that point of insertion/deletion through the rest of
the mRNA code. This is called a frameshift
mutation
Types of Chromosomal
Mutations
Deletion
Duplication
Inversion
Translocation
Chromosomal Mutations


Changes in the number or structure of
the chromosomes themselves
Occur when part of a chromosome
breaks off and is lost, reattached in
reverse order, or attached to a different
chromosome.
Mutagens
Chemical agents that affect the DNA
ex: pesticides, tobacco smoke,
formeldyhyde
 Physical agents in the environment
ex: UV radiation from the sun,
electromagnetic radiation, radon.

Repair mechanisms
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Repair mechanism that fix mutations n
cells have evolved. Much like a book
editor, enzymes proofread the DNA and
replace mistakes with the correct
nucleotide. However, the greater the
exposure to a mutagen, the more likely
a mistake will not be corrected.
the problem with tanning booths…….
Gene Expression and Environment

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Both the internal and external environment of
the cells can influence which genes are
activated in the cell. Some of this influence
may occur during the development, leading
to the many different types of cells that an
organism needs.
Although genes are inherited, an organism’s
environment can affect the ways some genes
are revealed, or expressed.
Examples of
gene/environment interaction:
1. Effect of light on
chlorophyll production.
 Without light, a yellow
pigment is produced
 With light, a green
pigment is produced.

2). Effect of temperature
on the hair color in
Himalayan rabbits.

body fur is - white

on the tail, feet, nose,
ears the fur is – black
This is because the
temperature is cooler on
these parts of the rabbits
body.
 If Ice is applied to skin of
rabbit, black fur will grow.