intro chapter 10 part1a
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Chapter 10
Molecular Biology of the GenePart 1
Molecular GeneticsMolecular genetics looks at
how genes work on the molecular level.
Studying molecular genetics means studying DNA, RNA
and proteins.
Molecular GeneticsDNA
Our genes are located on the DNA which combines with proteins to make
our chromosomes.DNA is composed of many monomer
units called nucleotides (composed of a deoxyribose sugar, a phosphate
and 1 of 4 nitrogen bases.
Molecular GeneticsNitrogen bases
Molecular GeneticsNucleotide
Molecular GeneticsDNA
The strands of the DNA molecule are composed of the nucleotides
connected sugar to phosphate (making a sugar-phosphate
backbone) with the nitrogen bases dangling off to one side.
Molecular GeneticsDNA strand
Molecular GeneticsDNA
DNA has 2 strands that link to each other with hydrogen bonds between the nitrogen
bases.When matching DNA with DNA the bases
always match up as follows:Adenine – ThymineThymine – AdenineGuanine – CytosineCytosine – Guanine.
Molecular GeneticsDNA double strand
Molecular GeneticsDNA
The two strands run in opposite directions from one another. One
strand is called the 35 strand, while the other is called the 53 strand.The numbers just refer to how the phosphates attach to the sugar’s
carbon atoms.
DNA antiparallel strands
Molecular GeneticsDNA Replication
During the S phase of the cell cycle, the DNA must replicate itself so that
the cell can divide.
The DNA present in the cell serves as a template upon which new DNA will
form.
Molecular GeneticsDNA Replication
One new strand of DNA will form along each of the two original strands
of DNA.The resulting sister chromatids will
each have one original strand and one new strand. This is called the
semi-conservative model.
Molecular GeneticsDNA Replication
Molecular GeneticsDNA Replication
Older, now discarded theories were: 1) that the old DNA was destroyed and two brand new DNA molecules
made (non-conservative).2) that one of the final 2 DNA
molecules was the original and the other was entirely new (conservative).
Molecular GeneticsThis is a short piece of DNA.This will serve as the template or “mother” DNA upon which copies can be made.
Original 35
strand
AG
T C
G C
C T
GA
TG
C T
A T
G C C
A C T
Original53strand
TC
AG
GC
GA
CT
AC
GA
TA
CGG
TGA
Molecular GeneticsDNA Replication
The process of DNA replication begins with the DNA molecule
opening up to allow the strands to be copied.
This is initiated by an enzyme called DNA polymerase. (an enzyme that
makes the DNA polymer).
DNA polymerase
Original53strand
Original 35
strand
C G T A
G CA T
A TCG
C G T A
A T
A T
G C C
G C
G
A T C
G
T
A
Molecular Genetics
Molecular GeneticsDNA Replication
Once the DNA has begun to open, nucleotides, floating freely in the
nucleoplasm, begin to come in and align themselves with their complementary mates
on the original DNA strands.These nucleotides will become new strands
connecting to each original strand.
Molecular Genetics
nucleotides
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C
T
G
A
Original53strand
Original 35
strand
C G T A
G CA T
A TCG
C G T A
A T
A T
G C C
G C
G
A T C
G
T
A
Molecular Genetics
nucleotides
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G C
T
C
T
G
A
Original53strand
Original 35
strand
C G T A
G CA T
A TCG
C G T A
A T
A T
G C C
G C
G
A T C
G
T
A
Molecular GeneticsDNA Replication
The DNA polymerase connects the sugar-phosphate backbones of the new strands but it can only add nucleotides from the 5 end to the
three end.On the original 35 strand, a new 53 strand
will be built. This strand is simple for the polymerase to join together. The enzyme
connects the nucleotides smoothly one by one all along the strand to the end.
Molecular Genetics
nucleotides
A
A
G
G
C
C
T
T
C
T
G
A
A
G
C
T C
T
G
Original 35
strand
C T
GA
TG
C T
A T
G C
CA C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
G
T
G
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
G
T
G
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
G
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
G
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG C
A
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
C
A
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TA
G
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TA
G
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
C
A
T
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
CA
T
NEW53strand
Molecular GeneticsA
C
C
T C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
CA
T
NEW53strand
Molecular Genetics
C
C
C
T
G
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
A
T
Original 35
strand
AG
C
C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
CA
TC
NEW53strand
G
A
Molecular Genetics
C
C
C
T
G
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
A
T
Original 35
strand
AG
C
C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
CA
TC
NEW53strand
G
A
Molecular Genetics
C
C
C
T
G
A
C
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
A
T
Original 35
strand
AG
C
C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
CA
TC
NEW53strand
GA
T
Molecular Genetics
C
C
C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
A
T
Original 35
strand
AG
T C
G C
C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
CA
TC
AG
T
CA
NEW53strand
Molecular Genetics
C
C
C
T
G
A
A
C T
C
T
G
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
A
T
Original 35
strand
AG
T C
G C
C T
GA
TG
C T
A T
G C C
A C T
GT
GG
CA
TAG
CA
TC
AG
T
CA
NEW53strand
G
Molecular Genetics
C
C
C
G
A
A
C
T
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
T
T
C
G
T
Original 35
strand
AG
T C
G C
AA
T
C T
GA
TG
C T
A T
G C C
A TGG
CA
TAG
CA
TC
AG
T
CG
A
AC
G
G
T
NEW53strand
Molecular Genetics
C
C
C
G
A
A
C
T
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
T
T
C
G
T
Original 35
strand
AG
T C
G C
AA
T
C T
GA
TG
C T
A T
G C C
A TGG
CA
TAG
CA
TC
AG
T
CG
A
AC
G
G
T
NEW53strand
Molecular Genetics
C
C
C
G
A
A
C
T
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
T
T
C
G
T
Original 35
strand
AG
T C
G C
AA
T
C T
GA
TG
C T
A T
G C C
A TGG
CA
TAG
CA
TC
AG
T
CG
A
AC
G
G
T
NEW53strand
Molecular Genetics
C
C
C
G
A
A
C
T
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
T
T
C
G
T
Original 35
strand
AG
T C
G C
AA
T
C T
GA
TG
C T
A T
G C C
A TGG
CA
TAG
CA
TC
AG
T
CG
A
AC
G
GT
NEW53strand
Molecular Genetics
C
C
C
G
A
A
C
T
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
T
T
C
G
T
Original 35
strand
AG
T C
G C
AA
T
C T
GA
TG
C T
A T
G C C
A TGG
CA
TAG
CA
TC
AG
T
CG
A
AC
G
GTT
A
NEW53strand
Molecular Genetics
C
C
C
G
A
A
C
T
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
T
T
C
G
T
Original 35
strand
AG
T C
G C
AA
T
C T
GA
TG
C T
A T
G C C
A TGG
CA
TAG
CA
TC
AG
T
CG
A
AC
G
GTT
A
NEW53strand
Molecular Genetics
C
C
C
G
A
A
C
T
C
T
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
T
T
C
G
T
Original 35
strand
AG
T C
G C
AA
T
C T
GA
TG
C T
A T
G C C
A TGG
CA
TAG
CA
TC
AG
T
CG
A
AC
G
GTT
A
NEW53strand
Molecular GeneticsDNA Replication
Building the new 35 strand using the original 53 strand as the template is a little
more difficult.Since polymerase can only add new bases
from the 5 end to the 3 end, it can only join the nucleotides together in short fragments
when building a 35 strand.
Molecular Genetics
nucleotides
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C
T
G
A
Original53strand
Original 35
strand
C G T A
G CA T
A TCG
C G T A
A T
A T
G C C
G C
G
A T C
G
T
A
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C T
G
A
Original53strand
GA
CT
AC
G
A
T
AC
G
G
T
G
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA
T
C
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA
T
C
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA
T
C
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
TG
A
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
TG
A
A
G
C
T
C T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
TG
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
TG
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
TG
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C T
TG
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C T T
G
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C T T
G
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C T T
G
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
G
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C
T
G
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
C
C
T
T
G
A
A
G
C
T
C
TG
A
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
C
C
T
T
G
A
T
C
TG
A
Original53strand
TC
AG
GC
T
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
C
C
T
T
G
A
T
C
TG
A
Original53strand
TC
AG
GC
T
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
C
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
C
C
T
T
G
A
T
C
TG
A
Original53strand
TC
AG
GC
T
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
CG
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
C
C
T
T
G
A
T
C
TG
A
Original53strand
TC
AG
GC
T
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
CGA
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
C
C
T
T
G
A
T
C
TG
A
Original53strand
TC
AG
GC
T
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
CGA
C
NEW35
strand
Molecular Genetics
A
A
G
G
C
C
T
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
C
C
T
T
G
A
T
C
TG
A
Original53strand
TC
AG
GC
T
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
CGA
C
NEW35
strand
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A C
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A C
G
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A C
G T
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A C
G T
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A C
G T
T
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A C
G T
TA
NEW35
strand
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
A
G
G
C
T
C
C
T
T
G
T
C
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA
CGG
T
GA
CGA
C
A C
G T
TA
NEW35
strand
Molecular Genetics
A
C
T
A
G
C
Original 35
strand
A C T
GA
TG
C T
A T
G C
C
G
C
T
C
C
T
T
G
A
T
C
TG
A
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
GA
C
NEW35
strand
Molecular GeneticsDNA Replication
Once the fragments are made, another enzyme, DNA ligase, moves along the chain,
connecting the fragments to each other.
Molecular Genetics
C
C
T
T
G
A C
TG
A
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
GA
C
NEW35
strand
DNA ligase
Molecular Genetics
C
C
T
T
G
A C
TG
A
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
GA
C
NEW35
strandDNA ligase
Molecular Genetics
C
C
T
T
G
A C
TG
A
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
GA
C
NEW35
strand
DNA ligase
Molecular Genetics
C
C
T
T
G
A C
TG
A
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
GA
C
NEW35
strand
DNA ligase
Molecular Genetics
C
C
T
T
G
A C
TG
A
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
GA
C
NEW35
strand
DNA ligase
Molecular Genetics C
T
T
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA T
GA
CGA
C
A C
G T
TA
NEW35
strandDNA ligase
Molecular Genetics C
T
T
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA T
GA
CGA
C
A C
G T
TA
NEW35
strand
DNA ligase
Molecular Genetics C
T
T
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA T
GA
CGA
C
A C
G T
TA
NEW35
strand
DNA ligase
Molecular Genetics C
T
T
TG
A
Original53strand
TC
AG
GC
TT
A
GA
CT
AC
GA
TA T
GA
CGA
C
A C
G T
TA
NEW35
strand
DNA ligase
Molecular Genetics
C
C
T
T
G
A C
TG
A
Original53strand
TC
GA
CT
AC
GA
TA
CGG
TGA T
C
T
GA
GA
C
NEW35
strand
DNA ligase
Molecular GeneticsDNA Replication
The result is two identical “daughter” copies of the double stranded DNA
which are also identical to the original “mother” double stranded DNA.
Now we have two DNA molecules that are identical to each other and to the original DNA. These are sister chromatids. They are still connected to each other at the centromere
Molecular Genetics
A TA T
CG C G T A
A TA T
G C C G C G
A T C G T A
A TA T
CG C G T A
A TA T
G C C G C G
A T C G T A
Newly formed 5 3 strand
Original 35 strand
Original 53 strand
Newly formed 3 5 strand
centromere
Molecular GeneticsDNA Replication
This process does not just start at one end of the DNA and run through to the other end. That would take a very long time and there
is too much risk of error.Instead several points along the DNA open
up simultaneously. These points are called replication origin sites. As the DNA opens wider, these sites form replication bubbles.
Molecular GeneticsDNA Replication
Molecular GeneticsDNA Replication
At each replication site, DNA polymerase attaches to each strand and begins to run down the strand,
bringing in DNA nucleotides to line up with the nucleotides on the strand.
Molecular GeneticsDNA Replication
As the enzyme moves, the DNA opens more and the bubbles get
larger until they finally merge as the replication process is completed.
Molecular GeneticsDNA Replication
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