2. 4. Free nucleotides base pair to
original polynucleotide.
5. DNA polymerase
enzyme joins the
sugar phosphate
backbone.
6. An enzyme rewinds the
double helix
7. Two new
double helices
each containing
one of the original
polynucleotides
Key:
Red arrow: Original double helix
Blue arrow: Helicase
DNA’s main job
is to store
information, it is
a nucleic acid
made up of
nucleotides
joined into long
strands or
chains by
covalent bonds.
The nucleotides
that make up
DNA are
Adenine,
Thymine,
Cytosine, and
Guanine.
3. Unwinding-Replication
begins at a specific site in
the DNA called the origin
of replication. Unwinding
enzymes called DNA
helicases cause the two
parent DNA strands to
unwind and separate from
one another in both
directions at this site to
from two “Y”-shaped
replication forks. These
replication forks are the
actual site of DNA
copying.
Key:
-A polynucleotide chain can only elongate in one direction
-In the picture a new triphosphate is about to be added to
the growing chain.
4. Key:
-one of the new
polynucleotide chains can
elongate continuously.
-the other growing chain
does so in short lengths
which must later be joined
together.
Complementary pairing up of the nucleotide bases- Each separate DNA strand
now has its sequence of bases exposed and unpaired. Enzymes match up each one of
these exposed bases, in turn, with free nucleotide triphosphates; A with T, and G with
C. It is therefore the sequence of bases on an old original strand which dictates and
specifies the complementary order of bases on the newly created strand.
5. Key:
-One of the new
polynucleotide chains can
elongate continuously
-the other growing chain does
so in short lengths which
must later be joined together.
Continuous and Discontinuous- RNA are added to both strands of DNA in the 5’3’
direction. The replication fork opens unidirectional. The RNA primers are then extended in
the 5’ 3’ direction on both strands as DNA synthesis proceeds. On the leading strand,
synthesis is continuous because the primer is extended without interruption into the
replication fork as it continues to open to the right. On the lagging strand, synthesis is
discontinuous, since new RNA primers must be added as the opening of the replication
fork continues expose new template.
8. A-T
G-C
Cytosine- it’s a
compound found in living
tissue as a constituent
base of nucleic acids. It
is paired with guanine in
double strands DNA.
9. A-T
G-C
C-G
Guanine-a compound
that occurs in guano and
fish scales, and is one of
the four constituent bases
of nucleic acids. A purine
derivative, it is paired with
cytosine in double
stranded DNA.
10. A-T
G-C
Thymine- a compound
that is one of the four
constituent bases of
nucleic acids. A
pyrimidine derivative, it
is paired with adenine
in double-stranded
DNA.
C-G
T-A
21. Mutations
In genetics, a mutation is a change of the nucleotide
sequence of the genome of an organism, virus, or extra
chromosomal genetic element.
Mutations result from unrepaired damage to DNA or to
RNA genomes (typically caused by radiation or chemical
mutagens)
Errors in the process of replication, or form the insertion
or deletion of segments of DNA by mobile genetic
elements.
22.
23. Meiosis
Meiosis is a special type of cell division necessary for
sexual reproduction in eukaryotes, such as animals,
plants and fungi.
The number of sets of chromosomes in the cell
undergoing meiosis is reduced to half the original number.
28. Mitosis
Mitosis is the process, in the cell cycle, by which a cell
duplicates into two genetically alike daughter cells.
In mitosis, chromosomes in the cell nucleus are separated
into two identical sets of chromosomes, each in its own
nucleus.
It is a form of nuclear division.
