DNA & Protein Synthesis

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14 Δεκ 2012 (πριν από 4 χρόνια και 10 μήνες)

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DNA Replication &
Protein Synthesis


The student will investigate and
understand common mechanisms of
inheritance and protein synthesis.


Key concepts include:


f) the structure, function, and replication of
nucleic acids (DNA and RNA); and


g) events involved in the construction of
proteins.


The student will investigate and
understand common mechanisms of
inheritance and protein synthesis.


Key concepts include:


h) use, limitations, and misuse of genetic
information; and


i) exploration of the impact of DNA
technologies.

History


Before the 1940’s scientists didn’t know
what material caused inheritance.


They suspected it was either DNA or
proteins.


History


A series of experiments proved that DNA
was the genetic material responsible for
inheritance.

History



In
1952
, Alfred
Hershey and Martha
Chase did an
experiment using a
virus that infects
E.
coli

bacteria.



The experiment
proved that DNA and
not protein is the
factor that influences
inheritance.

History


Erwin Chargaff
discovered the base
pairing rules and ratios
for different species.


Adenine pairs with
Thymine


Cytosine pairs with
Guanine.

History


Rosalind Franklin & Maurice Wilkins had
taken the 1
st

pictures of DNA using X
-
ray
crystallization

This proved that DNA had a helical
shape.

History


The Nobel Prize in Medicine
1962


Francis Harry Compton Crick


James Dewey Watson


Maurice Hugh Frederick Wilkins


Rosalind Franklin

(Died of cancer
1958
)

Wilkins has become a
historical footnote and
Watson & Crick are
remembered as the
Fathers of DNA

Watson

Crick

DNA


O

O=P
-
O


O

Phosphate


Group

N

Nitrogenous base


(A, T
,

G, C)

CH2

O

C
1

C
4

C
3

C
2

5


Sugar

(deoxyribose)

Nitrogen Bases


2 types of Nitrogen Bases


Purines


Double ring


G & A



Pyrimidines


Single ring


C & U & T

PGA

CUT PY

DNA
-

double helix

P

P

P

O

O

O

1

2

3

4

5

5

3

3

5

P

P

P

O

O

O

1

2

3

4

5

5

3

5

3

G

C

T

A

T

A

DNA


The genetic code is a
sequence of DNA
nucleotides in the
nucleus of cells.


DNA


DNA is a double
-
stranded molecule.


The strands are
connected by
complementary
nucleotide pairs (A
-
T &
C
-
G) like rungs on a
ladder.


The ladder twists to form
a
double helix
.

DNA


During S stage in
interphase, DNA
replicates itself.


DNA replication is
a semi
-
conservative
process.

DNA


Semi
-
conservative
means that you
conserve part of
the original
structure in the
new one.



You end up with
2
identical strands of
DNA.

DNA


Gene

-

a segment of
DNA that codes for a
protein, which in turn
codes for a trait (skin
tone, eye color, etc.)



A gene is a stretch of
DNA.

DNA


A mistake in DNA
replication is called a
mutation.



Many enzymes are
involved in finding and
repairing mistakes.


Mutations


What causes mutations?


Can occur spontaneously


Can be caused by a mutagen



Mutagen: An agent, such as a chemical,
ultraviolet light, or a radioactive element,
that can induce or increase the frequency
of mutation in an organism.

Mutations


Some mutations can:



Have little to no effect



Be beneficial (produce organisms that are
better suited to their environments)



Be deleterious (harmful)


Mutations


Types of mutations


Point Mutations or Substitutions
: causes
the replacement of a single base
nucleotide with another nucleotide



Missense
-

code for a different amino
acid


Nonsense
-

code for a stop, which can
shorten the protein


Silent
-

code for the same amino acid
(AA)


Mutations


Example: Sickle Cell Anemia

Mutations


Types of mutations


Frame Shift Mutations
: the
number of nucleotides
inserted or deleted is not a
multiple of three, so that
every codon beyond the
point of insertion or deletion
is read incorrectly during
translation.


Ex.: Crohn’s disease

Insertion

Deletion

Mutations


Types of mutations


Chromosomal Inversions
: an entire section of
DNA is reversed.


Ex.: hemophilia,

a bleeding disorder

DNA Repair


A complex system of
enzymes, active in the G
2

stage of interphase,
serves as a back up to
repair damaged DNA
before it is dispersed into
new cells during mitosis.

RNA


O

O=P
-
O


O

Phosphate


Group

N

Nitrogenous base


(A,
U

,

G, C )

CH
2

O

C
1

C
4

C
3

C
2

5


Sugar


(ribose)

RNA


Function: obtain
information from
DNA & synthesizes
proteins



3 differences from DNA

1.
Single strand
instead of double
strand


2.
Ribose instead of
deoxyribose


3.
Uracil instead of
thymine

3 types of RNA

1.
Messenger RNA

(mRNA)
-

copies information from DNA
for protein synthesis


Codon
-

3 base pairs that

code for a single amino

acid.

codon

3
types of RNA

2.
Transfer RNA

(tRNA)
-

collects amino acids for
protein synthesis



Anticodon
-
a sequence
of 3 bases that are
complementary base
pairs to a codon in the
mRNA

3
types of RNA

3.
Ribosomal RNA

(rRNA)
-

combines with proteins to form
ribosomes

Amino Acids


Amino acids
-

the
building blocks of
protein



At least one kind of tRNA
is present for each of the
20 amino acids used in
protein synthesis.

Transcription

-

mRNA is made from DNA
& goes to the ribosome

Translation

-

Proteins are made from the
message on the mRNA


Transcription


In order for cells to make
proteins, the DNA code
must be transcribed
(copied) to mRNA.


The mRNA carries the
code from the nucleus to
the ribosomes.

Translation


At the ribosome,
amino acids (AA)
are linked together
to form specific
proteins.


The amino acid
sequence is
directed by the
mRNA molecule.

ribosome

Amino acids

Make A Protein


DNA sequence

ATG AAA AAC AAG GTA TAG




mRNA sequence

UAC UUU UUG UUC CAU AUC

Make mRNA


mRNA sequence

UAC UUU UUG UUC CAU AUC



tRNA sequence

AUG AAA AAC AAG GUA UAG

Make mRNA


tRNA sequence

AUG AAA AAC AAG GUA UAG



Amino Acid sequence

met lys asn lys val stop

Human Genome Project



The Human Genome Project is a
collaborative effort of scientists around the
world to map the entire gene sequence of
organisms.



This information will be useful in detection,
prevention, and treatment of many genetic
diseases.

DNA Technologies


DNA technologies
allow scientists to
identify, study, and
modify genes.



Forensic identification
is an example of the
application of DNA
technology.

Gene Therapy


Gene therapy is a technique for correcting
defective genes responsible for disease
development.


Possible cures for:


diabetes


cardiovascular disease


cystic fibrosis


Alzheimer's


Parkinson’s


and many other diseases is possible.

Genetic Engineering



The human manipulation of the genetic
material of a cell.


Recombinant DNA
-

Genetically
engineered DNA prepared by splicing
genes from one species into the cells of
a different species. Such DNA becomes
part of the host's genetic makeup and is
replicated.

Genetic Engineering



Genetic engineering techniques are used in
a variety of industries, in agriculture, in
basic research, and in medicine.

This genetically
engineered cow
resists infections of
the udders and can
help to increase dairy
production.

Genetic Engineering



There is great potential for the development
of useful products through genetic
engineering


EX., human growth hormone, insulin, and pest
-

and disease
-
resistant fruits and vegetables

Seedless
watermelons are
genetically
engineered

Genetic Engineering



We can now grow new body parts and soon
donating blood will be a thing of the past,
but will we go too far?

Photo of a mouse
growing a "human ear"