Download DNA Replication

Genetics: field of biology that studies
genes and their inheritance
Gene
Segment of DNA
that encodes a
functional
product, usually a
protein
Genome = All of the genetic material (DNA) in a
cell.
 Prokaryotic cell has only one genome located in the
nuclear area.
 Eukaryotic cell has 2 genomes
 Nuclear genome
 Mitochondrial genome
 If not specified, “genome” usually refers to the
nuclear genome.


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In human beings genes constitute only 3 % of
the human genome.
The remaining 97 % of the genome – have yet
no known functions! These regions are called
non-coding regions.
Genome = Coding regions (genes) + noncoding regions.

Genetics is the study of single specific,
individual genes in isolation and their role in
inheritance

e.g. "monogenic" diseases such as sickle cell
anaemia and cystic fibrosis, caused by an
error in a single gene
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Genomics is the study of all the genes in the
genome and the interactions among them
and their environment (or non-genetic
factors such as a person's lifestyle)
Improve understanding of complex diseases
such as diabetes, heart disease, and asthma


Genetics is the study of single specific,
individual genes in isolation and their role in
inheritance
e.g. "monogenic" diseases such as sickle cell
anemia and cystic fibrosis, caused by an
error in a single gene.
• "Genotype" is an organism's full hereditary
information.
• "Phenotype" is an organism's actual observed
properties, such as morphology, development,
or behaviour
Structure and Function of Genetic Material

Genetic Material = DNA or RNA
▪ In the vast majority of organisms, genetic
material is DNA (deoxyribonucleic acid)
▪ In some viruses , genetic material is RNA
(ribonucleic acid)
Genetic Material: Basic Building Units
• Nucleotides
• Phosphate group
• Pentose sugar
• Nitrogenous base

Double stranded (double helix)

Adenine (A), thymine(T),
cytosine(C) and guanine(G)

"Backbone" is deoxyribose-phosphate

Strands held together by hydrogen
bonds between AT and CG

5’ to 3’ (strands are anti-parallel)

Complimentary base pairing
 A-T
• G-C
Hydrogen
bonds

Bacteria have closed, circular DNA

E. coli
 4 million base pairs
 1 mm long (over 1000 times longer that actual
bacterial cell)
 DNA takes up around 10% of cell volume
Helicases
Single stranded DNA
binding protein
Polymerase III
3’
5’
DNA template
RNA Primase
1
Synthesizing leading strand
starts by binding a short RNA
segment (primer) to single
DNA template by RNA primase
in 5’ to 3’ direction.
2
3
DNA Replication
Polymerase III finishes
the building up of
leading strand
continuously in 5’ to 3’
direction
Finally, polymerase I,
a cousin of
polymerase III,
replaces RNA primer
with DNA.
RNA primers
In the synthesis of the
lagging strand, the
helix uncoiling occurs
in
the
opposite
direction
to which
polymerase III works.
Therefore,
the
process has to be
done in pieces (notcontinous).
These
pieces are called
Okazaki fragments.
Polmerase III
synthesizes short
DNA segments
between RNA
primers.
Polymerse I replaces
RNA primers with
DNA.
Finally, DNA
ligase enzyme
binds DNA
pieces together
to create
lagging strand