Download DNA (Deoxyribonucleic Acid)

DNA
(Deoxyribonucleic Acid)
RNA
(Ribonucleic Acid)
Both DNA and RNA
• Are Nucleic Acids
– Macromolecules
essential for Life
• Have backbones of
made of a sugar and
phosphate group
P
P
P
• Both have contain
four nitrogenous
bases attached to
the backbone
• Only certain bases
are a part of DNA
and RNA
• The phosphate
group, sugar and
nitrogen bases
make a nucleotide.
Nucleotide
Phosphate
Group
O
O=P-O
O
5
CH2
O
N
C1
C4
Sugar
C3
C2
Nitrogenous base
What makes DNA and RNA different from
each other?
– Structure (Single or Double stranded)
– The sugar (Deoxyribose or Ribose)
– Nitrogenous Bases on the Nucleiotide (ACTG
or ACUG)
– Function in the organisms (Holding
information to code for specific protein that
determines an organism’s traits, OR to copy
instructions on how the protein should be
assembled)
DNA vs. RNA
• DNA
– Double Helix (double
stranded
– Looks like a twisted
ladder
5 O
P
3
3
O5
5 O
1
G
4
P
P
3
C
2
3
5
• DNA
O
2
3
4
1
A
P
O5
3
P
T
O5
P
– Sugar is Deoxyribose
– This gives DNA it’s
name of
Deoxyribonucleic Acid.
• DNA
T
A
G
C
– Nitrogen bases are
• Adenine (A)
• Thymine (T)
• Cytosine (C)
• Guanine (G)
• A always pairs with T
• G always pairs with C
BASE-PAIRINGS
H-bonds =Very weak bonds
G
C
T
A
• DNA
• The function of DNA is to hold the
information that codes for certain proteins
which determine an organism’s traits.
• It is the master copy of information for the
organism. When the cell is replicated it
has to make copies of its DNA before it
can divide.
• This process is called DNA replication.
DNA Replication
• DNA must be copied before a
cell can divide.
• This is called DNA Replication.
• The DNA molecule produces 2
IDENTICAL new complementary
strands following the rules of
base pairing:
A-T, G-C
•Each strand of the
original DNA serves as
a template for the new
strand
DNA Replication
Watson and Crick
showed: the two
strands of the parental
molecule separate,
and each functions as
a template for
synthesis of a new
complementary
strand.
.
DNA Template
Parental DNA
New DNA
•
•
•
•
•
•
•
•
•
•
•
•
A---?
G---?
C---?
T---?
A---?
G---?
A---?
G---?
C---?
A---?
G---?
T---?
•
•
•
•
•
•
•
•
•
•
•
•
A---T
G---C
C---G
T---A
A---T
G---C
A---T
G---C
C---G
A---T
G---C
T---A
DNA vs. RNA
• RNA
– Single stranded
– Looks like one-half
of a zipper
• RNA
– Ribose sugar
– This is where RNA
gets it’s name of
Ribonucleic Acid.
Ribose
• RNA
– Nitrogen bases are
• Adenine (A)
• Uracil (U)
• Cytosine (C)
• Guanine (G)
• A always pairs with U
• G always pairs with C
• Remember that DNA holds the instructions
for making proteins that code for certain
traits of an organism.
• RNA copies the instructions, carries it to
the appropriate part of the cell and
translates it into the amino acids that code
for proteins.
• RNA takes the info from DNA to make
proteins
Car Analogy
From DNA to Proteins
1.One type of RNA, messenger RNA, copies
the information from DNA in the nucleus,
and brings these instructions to the cell’s
factory floor, the cytoplasm.
This process is called Transcription.
2. On the factory floor, mRNA moves to the
assembly line, a ribosome.
3. The ribosome, made of Ribosomal RNA,
binds to the mRNA and uses the
instructions to assemble the amino acids
in the correct order.
4. The third type of RNA, transfer RNA is the
supplier. tRNA delivers amino acids to the
ribosome to be assembled into a protein.
This is called Translation.
• Three nitrogen bases
on mRNA= a codon
• Three nitrogen bases
on tRNA= an
anticodon
• Codon and
Anticodons code for
amino acids that
make proteins.
Genetic Diversity…
• Different
arrangements of
NUCLEOTIDES in a
nucleic acid (DNA)
provides the key to
DIVERSITY among
living organisms.
Genetic Changes
• DNA controls the structure and function of
the cell.
• So what happens when the sequence of
DNA nucleotides in a gene is changed?
– A substituted base in the DNA molecule changes the
structure of a protein
– Sometimes it may have little or no harmful effect.
– Other times, however, the change can cause the cell
to behave differently causing cancers or other harmful
effects.
Causes of Mutations
•
•
•
•
Errors in replication
Errors in transcription
Errors in cellular division
Or by external agents (environmental
factors)
– Too much exposure to radiation
– Pollutants
– Nutritional deficiencies
Gene Mutations
• Point Mutations – changes in
a single base part of
nucleotides
– Substitution
• THE FAT CAT ATE THE RAT
• THE FAT HAT ATE THE RAT
Gene Mutations
• Frameshift mutations- are mutations in
which a single base is added to or deleted
from DNA.
Gene Mutations
• Frameshift Mutations – shifts
the reading frame of the
genetic message so that the
protein may not be able to
perform its function.
– Insertion
• THE FAT CAT ATE THE RAT
• THE FAT HCA TAT ETH ERA T
– Deletion
H
• THE FAT CAT ATE THE RAT
• TEF ATC ATA TET GER AT
H
Repairing DNA
• Much like a book editor, enzymes
proofread the DNA and replace incorrect
nucleotides with correct nucleotides.
• These work well, but they are not perfect.
Mutations in Reproductive Cells
• If a mutation occurs in a reproductive cell
of an organism and this cell takes place in
fertilization, the altered gene would be
passed on to the offspring.
• Usually this is harmful to the offspring,
BUT occasionally the gene mutation has a
positive effect making them more likely to
survive.
• This can contribute to the evolution of the
species.
Mutations in the Body Cells
• If a mutation occurs in a nonreproductive
cell of the body such as in the skin, muscle
or bone, the mutation would not be passed
on to the offspring.
• The damage of the gene may impair the
function of the cell.
• If the mutation affects the cells ability to
control cellular division, the cell may begin
to divide uncontrollably resulting in
cancerous tumors.