2. 1. DNA
DNA is a Special molecule:
1. DNA stores and carries genetic
information from one generation to the
next.
2. DNA determines heritable
characteristics of organisms.
3. DNA is easily copied since it is
replicated during cell division.
3. The Structure of DNA:
Made of units called nucleotides.
Nucleotides include:
a. Deoxyribose (a sugar)
b. A Phosphate Group
c. One of four possible
Nitrogenous Bases…
4. The Four Nucleotides in DNA
1. Adenine (AD-un-
neen)
2. Thymine (THY-
meen)
3. Guanine (GWAH-
neen)
4. Cytosine (SY-to-
zeen)
Adenine Guanine
Cytosine
Thymine
Phosphate group Deoxyribose
5. Nucleotide Use
Like letters in the alphabet, these four
nitrogenous bases are strung together
in many different arrangements in order
to code for and carry genetic
information.
6. 2. The Structure of DNA
The Double Helix:
A. “A twisted ladder” forms when adenine and
thymine attract to each other.
-Cytosine and Guanine attract as well.
-So A=T and G=C in a DNA molecule
-This attraction (called Base Pairing) is caused
by hydrogen bonds between the bases.
7. More on the double helix
Two separate
and opposite
strands wrap
around each
other to form a
stable twisting
molecule
Nucleotide
Sugar-
phosphate
backbone
Hydrogen
bonds
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
8. 3. Chromosomes
Chromosomes are made of long strands of
DNA nucleotides wrapped around histone proteins.
1. The smallest of the 46 human chromosomes
contains 30 million (that’s 30,000,000) base
pairs.
2. There is 1 meter of DNA in each typical cell
nucleus in the human body
3. Tightly wrapped histones and DNA form
Chromatin while the cell is in interphase,
chromosomes when it is dividing.
9. 4. Chromatin
generally exists as
a long coiled
thread, but during
mitosis/meiosis it
becomes even
more coiled, this is
what is seen during
Prophase through
Anaphase and is
called a
chromosome
Chromosome Nucleosome
Supercoils
Coils
Histones
DNA
double
helix
10. 4. 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.
12. Process of DNA Replication:
1. Enzymes “unzip” a molecule of DNA
by breaking the hydrogen bonds
between base pairs.
2. The two strands unwind and each
becomes a template for the other
strand.
13. 3. New nucleotides 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 proof-
reads each strand so there are very few
mistakes.
14. RNA
The main role of RNA is to aid in Protein
Synthesis
RNA is similar to DNA in that both are
made of nucleotides
15. 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.
16. 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.
17. Transcription
Transcription is the process of making
RNA molecules from DNA molecules.
Transcription requires the enzyme
RNA Polymerase.
18. A Look at Transcription
Adenine (DNA and RNA)
Cytosine (DNA and RNA)
Guanine(DNA and RNA)
Thymine (DNA only)
Uracil (RNA only)
19. 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.
20. 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.
21. 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
22. The codons
for the
specific amino
acids are
listed using
this table:
24. How translation takes place
Protein
Chain
Ribosome
tRNA
Amino
acid
mRNA
tRNA
ribosome
mRNA
25. Putting it all together
DNA RNA Proteins Traits
Transcription Translation
•This simple phrase links all the important
genetic components together and is the basis
for the science of molecular biology
26. 6. Mutations
Mutations are mistakes cells make when
copying DNA.
The most common type of mutation is a
Point Mutation, this is when one nucleotide
is replaced by another.
These mutations sometimes alter the RNA
molecules transcribed and the proteins
translated by the ribosomes.
This type of mutation will take place on a
piece of DNA that codes for a protein and will
be known as a gene mutation
