intro nucleicacid pdf

8/6/2019 Intro NucleicAcid PDF

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Introduction inIntroduction intoto

Nucleic AcidsNucleic Acids

byby

Dr. Solachuddin J. A. Ichwan, PhDDr. Solachuddin J. A. Ichwan, PhD

KulliyyahKulliyyah of Dentistry- IIUMof Dentistry- IIUM


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George Shaw1856-1950

InheritanceLate last century, a young and beautiful actress

proposed marriage to the Nobel Laureate-

playwright,George Shaw.

We will have children who are not onlypretty likeme but also clever like you, the actress said

George Shaw replied, but my dear, what if they

getmy face andyour brain.


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Basic concepts of:

Nucleic Acids: DNA & RNAThe Central Dogma

Chromosome

Genetic code.

Objectives:


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Clone

Dolly, 1996 Snuppy, 2005

Genetic is becoming an increasingly important part of our lives


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DNA as legal evidence (Forensic DNA)

Paternity test

Who is the biological father?


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Genetic testing (diagnosis)

Genetic engineering & gene therapy

including the promise of medical treatments.


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Tissue regeneration


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The term "nucleic acid" is the generic name for a family of

biopolymers, named for their role in the cell nucleus.

Nucleic acids are universal in living things, as they are

found in all cells and viruses.

In biochemistry these molecules carry genetic information

or form structures within cells.

The most common nucleic acids are:

deoxyribonucleic acid (DNA)ribonucleic acid (RNA).

The monomers from which nucleic acids are constructed

are called nucleotides.

Nucleic acid


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Each nucleotide consists ofthree components:

1. a nitrogenous heterocyclic base (either a purine or a pyrimidine)2. a pentose sugar

3. a phosphate group.


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Double helix,

Double strands,

DNADNA

this structure was proposed in

1953 by two Nobel prize winners:

The main role of DNA is the long-termstorage of genetic information (DNA as

genetic material)


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18 August 2009 12Figure 1-2a Molecular Biology of the Cell, Fifth Edition ( Garland Science 2008)


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18 August 2009 13Figure 1-2d,e Molecular Biology of the Cell, Fifth Edition ( Garland Science 2008)

Majorgroove

Minorgroove


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each helix is a chain of nucleotides held together by

phosphodiesterbonds.

The strands are connected byFour nitrogen bases:

Adenin (A)

Guanine (G)

Purine

Cytosine (C)

Thymine (T)Pyrimidine


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Base pairing rules

CG A T

Purinesare always connected by Pyrimidine throughhydrogen bonds

GC bond is stronger than AT bond


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The two strands of DNA are

complimentary,

that means if one strand has the

sequence GCATG, the other strand

would be CGTAC

ATTGCGCTACTAACGCGATG

Antiparallel

Two backbones run in

opposite direction

one helix to 53 direction,

while another one into 35


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The DNA is furthercompacted by twisting the DNA in

each domain around itself, called supercoiling


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The DNA structure


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The total length of all the

strands of DNA in a cell(human) is 2 meters, all of

which to be packed into a

nucleus a few micrometers in

diameter.

This is achieved by the

formation of mixture DNA-

protein complex called

chromatin.

Chromatin makes up

chromosomes.


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Cell

THE NANOSIZETHE NANOSIZE

GENETIC MATERIALGENETIC MATERIAL


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How the DNA is packed


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Eukaryote

vs

Prokaryote

Where is the DNA?


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RNA

Messenger RNA (mRNA): is transcribed from DNA

(transcription), carrying information for protein synthesis.

Transfer RNA (tRNA): mediates recognition of the

codon and provides the corresponding amino acid

Ribosomal RNA (rRNA): the central component of the

ribosome's protein manufacturing machinery (translation).

Small nuclear RNA (snRNA): They are found within the nucleus of

eukaryotic cells and involved in a variety of important processessuch as DNA replication, RNA splicing etc.

Other Non-coding RNA: microRNAs, siRNAs, piRNAs, long

ncRNAs


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Location (in eukaryotes):Cytoplasm(except snRNA)

The pentose sugar unit is

ribose.

Less stable than DNA

Differences with DNA


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Uracil replaces thymine.

It is single strand polymer


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The 3 billions base of the human genome are not all in

one continuous strand of DNA.

Rather, the human genome is divided into 23 separate

pieces of DNA called chromosomes.

Chromosomes are composed ofchromatin. Human have 22 autosomes and the X, Y sex

chromosomes. (cells have two copies of each of thechromosomes).

Chromosomes


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Karyotype: The collection of all

chromosomes in an individual is

called


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The human chromosomes


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NOTE:Protein is never back-translated to RNA or DNA

DNA is never directly translated to protein.

The Central DogmaThe Central Dogma

Transcription

Translation

During replication, DNA is copied to DNA

DNA is transcribedto RNA is translatedto PROTEIN


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DNA is long-term storage

ofgenetic information.

Stable, packaged, and

inert.

Proteins are the 'programs' of the

cells.

They are the physical manifestations of

the abstract information recorded in thegenome.


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Gene:unit (segment) of DNA strand within the

chromosomes that can be inherited.

It carries the instruction for a specific function(protein synthesis).

Genetic code

For example, the globin gene contains instructions for

making the hemoglobin protein.There are more than 50000 different genes in human

body arranged on the 23 chromosomes.


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The sequence of bases in a DNA molecule carries the

information that specifies the orderof amino acids.


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The genetic code describes how base sequences are

converted into amino acid sequences during protein

synthesis (translation). The DNA sequence of a gene is divided into a series of

units of three bases.

Each set of three bases is called codon, which encode

a particular amino acid.

The four bases in DNA can combine as a total of 64codons, which specify the 20 amino acids found in

proteins.


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Since we have 20 amino

acids, this mean a single

amino acid can beencoded by more than

one codon

The codons that specify the

same amino acid are called

synonyms.


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The triplet code: Codon


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TO BE CONTINUEDO BE CONTINUED

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