intro chapter 10 part1a

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


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


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


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.


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.


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


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


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


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

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

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 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

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


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

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

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

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

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

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


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

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

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


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


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.


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.


As the enzyme moves, the DNA opens more and the bubbles get

larger until they finally merge as the replication process is completed.

intro chapter 10 part1a

Technology

c t c t g c t

t c g t

c c t c t g

g g c c t t c c t t

g t c g c t c

t c g c g t

g c t c t g

g g c c t t c t g