Title: DNA structure, RNA structure
1Molecular biology
2Nucleic acid
- Nucleic acids allow organisms to transfer genetic
information from one generation to the next. - First discovered by Friedrich Miescher from the
nuclei of the pus cell from discarded surgical
bandages and called it nuclein. - There are two types of nucleic acids
deoxyribonucleic acid, better known as DNA and
ribonucleic acid, better known as RNA. - When a cell divides, its DNA is copied and passed
from one cell generation to the next generation.
3Nucleic acid continue..
- Nucleic acids are composed of nucleotide
monomers. - Nucleotides contain three parts.
- A Nitrogenous Base
- A Five-Carbon Sugar
- A Phosphate Group
- DNA consists of the four nitrogenous
bases adenine (A), guanine (G), cytosine (C),
and thymine (T).
4Nucleic acid continue.
- DNA and RNA each consists of four different
nucleotides. - All nucleotides have a common structure
a phosphate group linked by a phosphoester bond
to a pentose (a five-carbon sugar molecule) that
in turn is linked to an organic base. - In RNA, the pentose is ribose in DNA, it
is deoxyribose. - The bases adenine, guanine, and cytosine are
found in both DNA and RNA thymine is found only
in DNA, and uracil is found only in RNA.
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7Nucleosides and nucleotides
Base Ribonucleoside Deoxyribonucleoside
Adenine Adenosine (A) deoxyadenosin (dA),
Guanine Guanosine (G) deoxyguanosine (dG)
Cytosine Cytidine (C) deoxycytidine(dC)
Uracil Uridine (U) deoxyuridine(dU)
Thymine Ribothymine (T) Deoxythymidine(dT)
Base Ribonucleotide Deoxynucleotide
Adenine AMP,ADP,ATP dAMP,dADP,dATP
Guanine GMP,GDP,GTP dGMP,dGDP,dGTP
Cytosine CMP,CDP,CTP dCMP,dCDP,dCTP
Uracil UMP,UDP,UTP dUMP,dUDP,dUTP
Thymine rTMPTDP,TTP dTMP,dTDP,dTTP
8Chemical structure of ATP
ATP -gt ADP P energy, orATP -gt AMP 2P
energy
9Polynucleotide
- Polynucleotide formed by condensation of two or
more nucleotides. - Occurs between the alcohol of a 5 phosphate of
one nucleotide and 3-hydroxyl of a second with
the elimination of H2O, forming a phosphodiester
bond. - The primary structure of DNA and RNA proceeds in
5 to 3 direction. - Common presentation 5-pGpApTpC-3
10Polynucleotide
11Watson and crick model
- In 1953 using x-ray diffraction
- Nobel prize
- Watson and crick ds helix model describe the
features of B form of DNA - Other forms are A and Z
12Watson and crick model
13DNA double helix
14Types of DNA
15Types of DNA
- B- DNA
- The B-form of DNA is the most common form of
DNA. - The B-DNA when compared to the A-DNA is more
narrower and elongated. - The major groove is wider and is more accessible
to proteins. - The minor groove is narrow. Â
- Helix diameter  23.7 Å
- Rise per Base pair  3.4 ÅÂ
- Base-pair per helical turn 10Â
16Types of DNA
- A- DNA
- A-form of DNA are shorter and wider than the
B-DNA. - Most of the RNA and RNA-DNA duplex are found
in this form. - The major groove is deep and narrow and is not
easily accessible to proteins. - The minor groove is wide, shallow is accessible
to proteins. - The base pairs are tilted to the helical axis.Â
- Helix diameter 25.5 Å
- Rise per base pair 2.3Â Ã…
- Base pair per helical turn  11
17Types of DNA
- Z-DNA
- Z-form of DNA has left handed sense.Â
- This structure of DNA is more narrower and
elongated than A or B helix. Major groove is not
prominent. - The minor groove is narrow.Â
- The base pairs are nearly perpendicular to helix
axis. - Helix Diameter 18.4 Å
- Rise per base pair 3.8Â Ã…Â
- Base pair per helical turn  12
18Types of DNA
19DNA Biological Functions
- Proteins
- DNA carries the codes for proteins. However, the
actual protein differs a lot from the codes
present on the DNA. The basic steps include - Transcription
- Translation
- DNA replication
- DNA inheritance
20RNA
- RNA- Ribonucleic acid, a nucleic acid present in
all living cells. Its principal role is to act as
a messenger carrying instructions from DNA for
controlling the synthesis of proteins, although
in some viruses RNA rather than DNA carries the
genetic information.
21RNA structure
22RNA type Functions
mRNA Carries genetic information copied from DNA in form of three base code
tRNA Transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation.
rRNA In the cytoplasm, ribosomal RNA and protein combine to form a nucleoprotein called a ribosome. The ribosome binds mRNA and carries out protein synthesis.Â
SnRNA Found with nucleus of eukaryotic cells. Involve in RNA splicing and maintain the telomeres.
23RNA type Functions
Small silencing RNA 20-30 nt. First discovered in 1993 Regulate biological pathways Types-SiRNA, miRNA, and Piwi-interacting RNA
Tm RNA Only found in bacteria Recognizes ribosomes that have trouble translating or reading an mRNA, unfinished protein that may detrimental to the cell. TmRNA help in destructing or proteolysis of these unfinished RNA or protein .
24rRNA
25mRNA
26tRNA
27RNA silencing
- RNA interfence- RNA silencing-post-transcriptional
gene silencing or RNA interference  gene
silencing, effects by which the expression of one
or more genes is down regulated or entirely
suppressed by small RNAs- si,mi and pi RNA
28Function of SiRNA
- Potential to be used for therapeutic purposes
where disease-causing genes are selectively
targeted and suppressed. - Eg. Cancer, HIV infection and hepatitis.
29Ribozymes
- Ribozymes (ribonucleic acid enzymes), also
termed catalytic RNA, are RNA molecules that are
capable of catalyzing specific biochemical
reactions, similar to the action of
protein enzymes. - 1982 discovery
- Ribozymes demonstrated that RNA can be both
genetic material (like DNA) and a
biological catalyst (like protein enzymes). - Contributed to the RNA world hypothesis, which
suggests that RNA may have been important in the
evolution for its self-replicating systems. - Discovered by Sidney Altman and Thomas Czech, who
were awarded the Nobel Prize in Chemistry in
1989.
30Ribozymes
- Function
- Ribozymes function (as part of the large subunit
ribosomal RNA) to link amino acids during protein
synthesis. - Includes  RNA splicing- spliceosome
- Hammerhead ribozymes
- VS ribozymes
- Leadzymes
- Hairpin ribozymes
31spliceosome