WARM-UP
If the DNA sequence is --AAA TAT CCG TAG CAA ATG
Write the mRNA sequence, tRNA anticodon
sequence, and the six amino acids.
DNA:
AAA TAT CCG TAG CAA ATG
mRNA:
tRNA:
Amino acids:
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Review
Chromosomes v. Genes v. DNA
• Chromosomes
contain genetic
information
• Genes are
sections of
chromosomes
• Segments of
genes are called
DNA
DNA and RNA are
examples of what major
macromolecule?
Nucleic Acids
What are the other
3 macromolecules?
-Lipids
-Carbohydrates
-Proteins
3
What does DNA stand for?
Deoxy-ribo-nucleic acid
• DNA is often called the blueprint of life
• DNA contains the instructions for what
traits (eye/hair color, etc.)
are inherited from
generation to generation
• Where is it found? Nucleus
4
DNA Structure
• Composed of sub-units called Nucleotides
• Nucleotides can be broken down into 3 parts
1. Phosphate Group
2. Deoxyribose Sugar (5 carbon sugar)
3. Nitrogenous Base
• Cytosine (C)
• Guanine (G)
• Adenine (A)
• Thymine (T)
1. Phosphate
3. Nitrogenous Base
2. Deoxyribose Sugar
(A, T, G, C)
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The Shape of DNA
• The basic shape is like
a twisted ladder or
zipper.
– This is called a
double helix, which
means it is double
stranded
“Rungs of ladder”
Nitrogenous
Base (C,G, A or T)
“Legs of ladder”
Phosphate &
Sugar Backbone
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One Strand of DNA
• One strand of DNA
is a polymer of
nucleotides.
• One strand of DNA
has many millions
of nucleotides.
nucleotide
phosphate
deoxyribose
bases
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Nucleotides
O
O -P O
O
O
O -P O
O
One deoxyribose together
with its phosphate and base
make a nucleotide.
O
O -P O
O
Phosphate
Nitrogenous
base
O
C
C
C
O Deoxyribose
8
5
DNA
O
3
3
P
5
O
O
C
G
1
P
5
3
2
4
4
P
5
P
2
3
1
O
T
A
3
O
3
5
O
5
P
P9
Double Stranded DNA
• Remember, DNA has
2 strands that fit
together like a zipper.
• The teeth are the
nitrogenous bases but
why do they stick
together?
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Chargaff’s Rule
• They stick together because of
hydrogen bonds of the nitrogenous
bases
• Adenine always pairs with Thymine
–A
T
• Cytosine always pairs with Guanine
T
A
–C
G
G
C
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DNA by the Numbers
• Each cell has about 2
m of DNA.
• The average human
has 75 trillion cells.
• The average human
has enough DNA to go
from the earth to the
sun more than 400
times.
• DNA has a diameter of
only 0.000000002 m.
The earth is 150 billion m
or 93 million miles from
the sun.
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What about RNA?
Stands for: Ribo-nucleic acid
• Structure similar to DNA but different
– Nucleotides divided into 3 parts
1. Phosphate Group
2. Ribose Sugar
3. Nitrogenous Base
–
–
–
–
Adenine (A)
Uracil (U) (Replaces Thymine)
Guanine (G)
Cytosine (C)
– Single stranded
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How are DNA and RNA related?
• DNA codes for RNA, which guides
protein synthesis
– The reading and expression of genes is
from DNA to RNA to protein
– DNA -> RNA -> Protein = Central
Dogma of Biology
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DNA Structure
• Rosalind Franklin took
diffraction x-ray
photographs of DNA
crystals
• In the 1950’s, Watson &
Crick built the first model
of DNA using Franklin’s
x-rays
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DNA Nucleotide
Phosphate
Group
O
O=P-O
O
5
CH2
O
N
C1
C4
Sugar
(deoxyribose)
C3
C2
Nitrogenous base
(A, G, C, or T)
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Pentose Sugar
• Carbons are numbered clockwise
1’ to 5’
5
CH2
O
C1
C4
Sugar
(deoxyribose)
C3
C2
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Antiparallel Strands
• One strand of
DNA goes from
5’ to 3’ (sugars)
• The other
strand is
opposite in
direction going
3’ to 5’ (sugars)
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Nitrogenous Bases
• Double ring PURINES
Adenine (A)
Guanine (G)
A or G
• Single ring PYRIMIDINES
Thymine (T)
Cytosine (C)
T or C
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Base-Pairings
• Purines only pair with
Pyrimidines
• Three hydrogen bonds
required to bond Guanine
& Cytosine
3 H-bonds
G
C
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•Two hydrogen bonds are
required to bond Adenine &
Thymine
T
A
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DNA
Replication
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3 Questions about
DNA Replication
1. What is DNA Replication? the
process where DNA make a copy of itself
2. Why does DNA need to copy?
Simple: Cells divide for an organism to
grow or reproduce, every new cell needs
a copy of its DNA or instructions to know
how to be a cell.
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3 Questions about
DNA Replication
3. When does DNA replication
occur?
– It occurs right before the cell
divides
– During the S Phase of
interphase of the cell cycle
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Synthesis Phase (S phase)
• S Phase during interphase of the
cell cycle
S
DNA replication takes
place in the S phase.
phase
G1
interphase
G2
Mitosis
-prophase
-metaphase
-anaphase
-telophase
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DNA Replication is Semiconservative
• The two strands of the parental molecule separate, and each
acts as a template for a new complementary strand
• In other words: when DNA makes a copy, one half of the OLD
strand is always kept in the NEW strand.
– This helps reduce the number of COPY errors.
• New DNA consists of 1 PARENTAL (original) and 1 NEW
strand of DNA
DNA Template
Parental DNA
New DNA
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Semiconservative
Replication
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Question:
• What would be the
complementary DNA
strand for the following
DNA sequence?
DNA 5’-CGTATG-3’
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Answer:
DNA 5’-GCGTATG-3’
DNA 3’-CGCATAC-5’
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1. What is the complimentary mRNA sequence to DNA sequence
A-T-T-G-C-A?
A. T-A-A-C-G-T
C. U-A-A-C-G-T
B. U-A-A-C-G-U
D. T-A-A-G-C-U
2. What causes the two sides of the double helix of DNA to stay joined
together?
A. joining of phosphate molecules
C. joining of base pairs
B. joining of sugar molecules
D. joining of RNA
3. What the three main parts of a nucleotide of DNA? (Choose all that Apply)
A. phosphate group
C. deoxyribose sugar
B. ribose sugar
D. nitrogenous base
4. The process whereby DNA unzips and makes a strand of mRNA is
called?
A. replication
C. translation
B. transcription
D. complementation
5. When does DNA replication occur?
A. During transcription
C. During translation
B. During mitosis
D. During the S phase of interphase
6. Determine the amino acids sequence from this mRNA sequence:
AUG CCC GGA UUA UAG (Use amino acid chart on board)
A. Met Pro Gly Leu Stop
C. Met Leu Pro Gly Stop
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B. Stop Leu Pro Gly Met
D. Met Pro Cys Gly Stop
Lesson Closure
3 things you learned in class today
2 questions you have about the
lesson
1 real-life connection
MIND MAPS
Create a map using all of the following terms
Be sure to link them together
DNA
Nucleotide
Transcription
Translation
Uracil
Ribose sugar
Amino acid
Nucleus
Double Helix
RNA
Thymine
chromosome
nucleic acid
deoxyribose sugar
mRNA
Unzipping
Protein
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