Download DNA - Miss Schwippert

DNA

Molecular basis of
herdity
How much DNA is in my body?
DNA is found in every cell (except red blood cells)
Each cell contains roughly 2 meters of DNA containing ~3
BILLION base pairs
The human body has ~ 10,000,000,000,0000 cells
If you unraveled all the DNA from all of your cells and
stretched it out end to end, it would stretch to the sun and back
several times!
You could fit 25,000 strands of DNA side by side in the width
of a human hair!
What is DNA?

Importance of DNA


DNA stands for
deoxyribonucleic acid.
It is one of two nucleic
acids found in the cell.
What is DNA?

Importance of DNA


DNA is the blueprint for life.
Every living thing uses
DNA as a code for making
proteins, which
determines traits.
What is DNA?

Importance of DNA

For example, DNA
contains the
instructions for making
the proteins (called
pigments) which give
your eyes color.
What is DNA?



DNA is packaged into
chromosomes.
Each chromosome is
composed of one
continuous DNA
molecule.
The DNA molecule is
wrapped around
proteins and coiled
tightly for protection
What is DNA?


Remember,
chromosomes are found
in the nucleus of
eukaryotic cells.
Prokaryotic cells have a
single chromosome
free-floating in the
cytoplasm.
Fill It In …
DNA
What?
Where?
Used for?
Discovery of DNA structure



Many scientists worked
to determine the source
of heredity.
Heredity is the passing
of traits from parent to
offspring.
But how are those traits
passed?
Video
Discovery of DNA structure

First, scientists
determined that
chromosomes
controlled heredity and
are made of DNA and
proteins.
Discovery of DNA structure

Then, scientists
determined DNA was
the chemical that
controlled
characteristics (traits
of the organism)
DNA Clearly Stated
Discovery of DNA structure

Then, the race was
on to reveal the
structure of the DNA
molecule
Discovery of DNA structure


Rosalind Franklin was the
first to take a clear
“picture” of DNA using a
technique called X-ray
crystallography
The “picture” offered a
clue of the shape of DNA
Discovery of DNA structure

Watson and Crick
received credit for finalizing
the model of DNA by using
the picture taken by
Franklin (given to them by
Franklin’s research
assistant - Maurice
Wilkins), and by
syntehsizing work
completed by other
scientists.
Structure of the DNA molecule


DNA is a double helix.
The double helix looks
like a twisted ladder.
Structure of the DNA molecule


The building blocks of
DNA are called
nucleotides.
A nucleotide consists of
three parts:



A sugar (named
deoxyribose)
A phosphate group
One of four nitrogen
bases
Structure of the DNA molecule

The four possible
nitrogen bases in a
DNA molecule are
named:




Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
Fill It In …
(From small to large)
N _____ base + sugar + phosphate
N __________
Two strands held together by _______ ______
D_______ H_________
Structure of the DNA molecule

There are two strands
of nucleotides in every
DNA molecule held
together by weak
hydrogen bonds
between the nitrogen
bases.
Structure of the DNA molecule




The nitrogen bases bond
in a specific way.
Adenine bonds with
thymine (A-T).
Guanine bonds with
cytosine (G-C).
This pattern is called
complementary base
pairing.
DNA Structure and
Function
Anti-parallel
strands

Nucleotides in DNA
backbone are bonded
from phosphate to sugar
between 3 & 5 carbons


5
3
3
5
DNA molecule has
“direction”
complementary strand
runs in opposite direction
Copying DNA

Replication of DNA


base pairing allows
each strand to serve
as a template for a
new strand
new strand is 1/2
parent template &
1/2 new DNA
Fill It In …
On this diagram:
 Highlight a
nucleotide
 Then write out the
NAME of the sugar
beside one of the
sugar molecules
 Finally, draw a box
around the
“backbone” and
label.
Check Yourself!
1.
How is DNA connected to your traits?
2.
What larger structure is composed of DNA?
3.
What two parts of the nucleotide make up the sides
(backbone) of a DNA molecule?
4.
What makes up one rung/”step” of the DNA “ladder”?
5.
What type of bond holds the rungs together?
Check Yourself!
1.
2.
3.
How is DNA connected to your traits? DNA CONTAINS
THE INSTRUCTIONS FOR MAKING PROTEINS
What larger structure is composed of DNA?
What two parts of the nucleotide make up the sides
(backbone) of a DNA molecule?
4.
What makes up one rung/”step” of the DNA “ladder”?
5.
What type of bond holds the rungs together?
Check Yourself!
1.
2.
3.
How is DNA connected to your traits? DNA CONTAINS
THE INSTRUCTIONS FOR MAKING PROTEINS
What larger structure is composed of DNA?
CHROMOSOMES
What two parts of the nucleotide make up the sides
(backbone) of a DNA molecule?
4.
What makes up one rung/”step” of the DNA “ladder”?
5.
What type of bond holds the rungs together?
Check Yourself!
4.
How is DNA connected to your traits? DNA CONTAINS
THE INSTRUCTIONS FOR MAKING PROTEINS
What larger structure is composed of DNA?
CHROMOSOMES
What two parts of the nucleotide make up the sides
(backbone) of a DNA molecule? SUGAR
(DEOXYRIBOSE) AND PHOSPHATE GROUP
What makes up one rung/”step” of the DNA “ladder”?
5.
What type of bond holds the rungs together?
1.
2.
3.
Check Yourself!
1.
2.
3.
4.
5.
How is DNA connected to your traits? DNA CONTAINS
THE INSTRUCTIONS FOR MAKING PROTEINS
What larger structure is composed of DNA?
CHROMOSOMES
What two parts of the nucleotide make up the sides
(backbone) of a DNA molecule? SUGAR
(DEOXYRIBOSE) AND PHOSPHATE GROUP
What makes up one rung/”step” of the DNA “ladder”?
(COMPLEMENTARY) NITROGEN BASE PAIRS
What type of bond holds the rungs together?
Check Yourself!
1.
2.
3.
4.
5.
How is DNA connected to your traits? DNA CONTAINS
THE INSTRUCTIONS FOR MAKING PROTEINS
What larger structure is composed of DNA?
CHROMOSOMES
What two parts of the nucleotide make up the sides
(backbone) of a DNA molecule? SUGAR
(DEOXYRIBOSE) AND PHOSPHATE GROUP
What makes up one rung/”step” of the DNA “ladder”?
(COMPLEMENTARY) NITROGEN BASE PAIRS
What type of bond holds the rungs together?
HYDROGEN BOND
Structure of the DNA molecule
Do all my cells have the same
DNA?

DNA replication
copies DNA for new
cells
What is DNA?
DNA replication


DNA is needed in each
cell to make necessary
proteins.
Because DNA is so
important, when a cell
divides, it must pass
on an exact copy of
the DNA to function
correctly.
DNA replication

Therefore, DNA is
copied (replicated)
during the S phase of
the cell cycle (part of
interphase, before
mitosis/meiosis)
Fill It In …
Enzyme Review!
 What are enzymes?

How do enzymes work?
Let’s meet
the team…
DNA Replication

Large team of enzymes coordinates replication
Process of DNA replication


An enzyme breaks the
weak hydrogen bonds
between the paired
nitrogen bases.
This allows DNA to
“unzip” as the two
strands move apart.
Replication: 1st step

Unwind DNA

helicase enzyme
unwinds part of DNA helix
 stabilized by single-stranded binding proteins

helicase
single-stranded binding proteins
replication fork
Process of DNA replication


The newly unpaired
nucleotides are paired
(A-T and G-C) with
extra nucleotides
present in the nucleus.
This process is
catalyzed by another
enzyme.
Process of DNA replication

Enzymes then link the
nucleotides along the
newly constructed
side of the DNA
ladder by bonding
sugar to phosphate.
Replication: 2nd step
 Build daughter DNA
strand
add new
complementary bases
 DNA polymerase III

DNA
Polymerase III
But…
Where’s the
We’re missing
ENERGY
something!
for the bonding!
What?
5
3
energy
Replication
DNA

Adding bases

can only add
nucleotides to
3 end of a growing
DNA strand


need a “starter”
nucleotide to
bond to
strand only grows
53
B.Y.O. ENERGY!
The energy rules
the process
Polymerase III
energy
DNA
Polymerase III
energy
DNA
Polymerase III
energy
DNA
Polymerase III
3
5
3
Replication fork / Replication
bubble
5
3
5
DNA polymerase III
leading strand
5
3
3
5
3
5
5
5
3
lagging strand
3
5
3
5
lagging strand
5
5
leading strand
growing
replication fork 5
3
growing
replication fork
leading strand
3
lagging strand
5 5
5
5
3
Starting DNA synthesis: RNA
primers
Limits of DNA polymerase
III

can only build onto 3 end of
an existing DNA strand
5
3
3
5
5
3
5
3
5
growing
3
replication fork
DNA polymerase III
primase
RNA 5
RNA primer


built by primase
serves as starter sequence
for DNA polymerase III
3
Replacing RNA primers with DNA
DNA polymerase I

removes sections of RNA
primer and replaces with
DNA nucleotides
DNA polymerase I
3
5
5
5
3
ligase
growing
3
replication fork
RNA
5
3
But DNA polymerase I still
can only build onto 3 end of
an existing DNA strand
Process of DNA replication

The DNA is proofread
by enzymes for any
errors.
Editing & proofreading DNA

1000 bases/second =
lots of typos!

DNA polymerase I

proofreads & corrects typos

repairs mismatched bases

removes abnormal bases


repairs damage
throughout life
reduces error rate from
1 in 10,000 to
1 in 100 million bases
Result of DNA replication



Two identical DNA
molecules have been
produced.
Each “daughter” DNA
molecule is composed
of one “old” strand and
one “new” strand
(Here a “strand” refers to
one chain of nucleotides)
Result of DNA replication

Each copy of DNA is
packaged as a
chromatid on a
doubled chromosome.
Result of DNA replication


After mitosis, each
daughter cell will receive
one of the two identical
copies of DNA.
This happens when the
doubled chromosome is
split, each new
chromosome going to a
new daughter cell.
DNA Replication
Amoeba Sisters
Fill It In …
Replication
 What?

Where?

Used for?

When?
Check Yourself!
1.
Why does each cell need DNA?
2.
3.
What is the name of the process which makes a
copy of DNA?
When does DNA replication occur?
4.
What catalyzes each step of DNA replication?
5.
At the end of DNA replication, each molecule is
composed of one _____ strand and one _____
strand.
Check Yourself!
3.
Why does each cell need DNA?
TO MAKE NECESSARY PROTEINS
What is the name of the process which makes a
copy of DNA?
When does DNA replication occur?
4.
What catalyzes each step of DNA replication?
5.
At the end of DNA replication, each molecule is
composed of one _____ strand and one _____
strand.
1.
2.
Check Yourself!
3.
Why does each cell need DNA?
TO MAKE NECESSARY PROTEINS
What is the name of the process which makes a
copy of DNA? REPLICATION
When does DNA replication occur?
4.
What catalyzes each step of DNA replication?
5.
At the end of DNA replication, each molecule is
composed of one _____ strand and one _____
strand.
1.
2.
Check Yourself!
1.
2.
3.
4.
5.
Why does each cell need DNA?
TO MAKE NECESSARY PROTEINS
What is the name of the process which makes a
copy of DNA? REPLICATION
When does DNA replication occur?
INTERPHASE/S-PHASE OF INTERPHASE
What catalyzes each step of DNA replication?
At the end of DNA replication, each molecule is
composed of one _____ strand and one _____
strand.
Check Yourself!
1.
2.
3.
4.
5.
Why does each cell need DNA?
TO MAKE NECESSARY PROTEINS
What is the name of the process which makes a
copy of DNA? REPLICATION
When does DNA replication occur?
INTERPHASE/S-PHASE OF INTERPHASE
What catalyzes each step of DNA replication?
ENZYMES
At the end of DNA replication, each molecule is
composed of one _____ strand and one _____
strand.
Check Yourself!
1.
2.
3.
4.
5.
Why does each cell need DNA?
TO MAKE NECESSARY PROTEINS
What is the name of the process which makes a
copy of DNA? REPLICATION
When does DNA replication occur?
INTERPHASE/S-PHASE OF INTERPHASE
What catalyzes each step of DNA replication?
ENZYMES
At the end of DNA replication, each molecule is
composed of one OLD strand and one NEW
strand.