All about DNA and replication process

2. (Dremstime,2016)
•DNA stands for deoxyribose nucleic acid
•This chemical substance is present in the nucleus
of all cells in all living organisms
•DNA is the genetic material, so it is responsible for carrying all the
hereditary information from one generation to another generation.
•DNA controls all the chemical changes which
take place in cells
•DNA is a very large molecule made up of a long
chain of sub-units
•The sub-units are called nucleotides. Each nucleotide is made up of
a sugar called deoxyribose
a phosphate group -PO4 and
an organic base
•Watson Crick found the structure of the DNA.
The model of DNA is called as double helix because two long strands
twist around each other like a ladder.
Sugar and phosphate molecules make the rails of the ladder.
Hydrogen bonds make the steps of the ladder.
Nucleotide is the basic building block of the DNA.

3. • “Ribonucleic acid,” a type of nucleic acid
• R = “ribose” (a type of sugar)
• Single stranded
• Can be found inside OR outside the nucleus
• RNA is more abundant than DNA.
• Pentose sugar in DNA is deoxyribose and in RNA its
ribose
• What nitrogenous bases are found in RNA?
 Adenine
 Guanine
 Cytosine
 Uracil (U) (There’s no thymine.)
• There are 3 types of RNA
1. mRNA: messenger RNA
2. tRNA: transfer RNA
3. rRNA: ribosomal RNA
(Dremstime,2016)

4. (mRNA)
 Messenger RNA (mRNA) carries
information about a protein sequence
to the ribosomes, the protein synthesis
factories in the cell
 It is coded so that every three
nucleotides (a codon) correspond to
one amino acid
 In eukaryotic cells, once precursor
mRNA (pre-mRNA) has been
transcribed from DNA, it is processed
to mature mRNA
 This removes its introns—non-coding
sections of the pre-mRNA
 The mRNA is then exported from the
nucleus to the cytoplasm, where it is
bound to ribosomes and translated into
its corresponding protein form with the
help of tRNA

5. (rRNA)
Ribosomal RNA (rRNA) is the
catalytic component of the ribosomes
 Eukaryotic ribosomes contain four
different rRNA molecules: 18S, 5.8S,
28S and 5S rRNA
 Three of the rRNA molecules are
synthesized in the nucleolus, and one
is synthesized elsewher
. In the cytoplasm, ribosomal RNA
and protein combine to form a
nucleoprotein called a ribosome
 The ribosome binds mRNA and
carries out protein synthesis
 Several ribosomes may be attached
to a single mRNA at any time.
Nearly all the RNA found in a typical
eukaryotic cell is rRNA.

6. (tRNA)
Transfer RNA (tRNA) is a small
RNA chain of about 80 nucleotides
 It transfers a specific amino acid
to a growing polypeptide chain at the
ribosomal site of protein synthesis
during translation
 It has sites for amino acid
attachment and an anticodon region
for codon recognition that binds to a
specific sequence on the messenger
RNA chain through hydrogen
bonding

7. Types of RNAs Primary Function(s)
mRNA - messenger translation (protein synthesis)
regulatory
rRNA - ribosomal translation (protein synthesis) <catalytic>
t-RNA - transfer translation (protein synthesis)
hnRNA - heterogeneous nuclear precursors & intermediates of mature mRNAs
& other RNAs
scRNA - small cytoplasmic signal recognition particle (SRP)
tRNA processing <catalytic>
snRNA - small nuclear
snoRNA - small nucleolar
mRNA processing, poly A addition <catalytic>
rRNA processing/maturation/methylation
regulatory RNAs (siRNA, miRNA,
etc.)
regulation of transcription and translation,

8. There are four levels of organization
1. Primary structure
2. Secondary structure
3. Tertiary structure
4. Quaternary structure
•Sequence of amino acids.
•Precise sequence can be
determined by gene.
•Changing of this sequence of
amino acid can change entire
protein.
•R group of the amino acids aid in
shaping the protein.
(Majordifferences,2015)

9. •Stretches or strands of proteins or peptides have distinct characteristic local
structural conformations or secondary structure, dependent on hydrogen
bonding.
• The two main types of secondary structure are the α-helix and the ß-sheet.
The α-helix is a right-handed coiled strand.
The side-chain substituent's of the amino acid groups in an α-helix extend
to the outside. Hydrogen bonds form between the oxygen of the C=O of each
peptide bond in the strand and the hydrogen of the N-H group of the peptide
bond four amino acids below it in the helix.
The hydrogen bonds make this structure especially stable. The side-chain
substituent's of the amino acids fit in beside the N-H groups.
The hydrogen bonding in a ß-sheet is between strands (inter-strand) rather
than within strands (intra-strand). The sheet conformation consists of pairs of
strands lying side-by-side.
The carbonyl oxygen's in one strand hydrogen bond with the amino
hydrogen's of the adjacent strand.
The two strands can be either parallel or anti-parallel depending on whether
the strand directions (N-terminus to C-terminus) are the same or opposite.
The anti-parallel ß-sheet is more stable due to the more well-aligned
hydrogen bonds.

10. •The overall three-dimensional shape of an entire protein molecule is the
tertiary structure.
•The protein molecule will bend and twist in such a way as to achieve
maximum stability or lowest energy state.
•Many proteins are made up of multiple polypeptide chains,
often referred to as protein subunits.
•These subunits may be the same (as in a homodimer) or
different (as in a heterodimer).
•The quaternary structure refers to how these protein subunits
interact with each other and arrange themselves to form a
larger aggregate protein complex.
•The final shape of the protein complex is once again
stabilized by various interactions, including hydrogen-bonding,
disulfide-bridges and salt bridges.

11. • The flow of information in the
cell starts at DNA, which
replicates to form more DNA.
Information is then
‘transcribed” into RNA, and
then it is “translated” into
protein. The proteins do most
of the work in the cell.
• Information does not flow in
the other direction. This is a
molecular version of the
incorrectness of “inheritance
of acquired characteristics”.
Changes in proteins do not
affect the DNA in a systematic
manner (although they can
cause random changes in
DNA.)

12. However, a few exceptions to the Central Dogma exist.
• Most importantly, some RNA viruses, called
“retroviruses” make a DNA copy of themselves using
the enzyme reverse transcriptase. The DNA copy
incorporates into one of the chromosomes and
becomes a permanent feature of the genome. The
DNA copy inserted into the genome is called a
“provirus”. This represents a flow of information from
RNA to DNA.
• Closely related to retroviruses are “retrotransposons”,
sequences of DNA that make RNA copies of
themselves, which then get reverse-transcribed into
DNA that inserts into new locations in the genome.
Unlike retroviruses, retrotransposons always remain
within the cell. They lack genes to make the protein
coat that surrounds viruses.

13. •Thinklink oy,(2015) Protein Synthesis
https://www.thinglink.com/scene/733810050967011330
•Manish Biyani and Takanori Ichiki (2014),
<http:http://www.intechopen.com/books/cell-free-protein-
synthesis/solid-phase-cell-free-protein-synthesis-to-
improve-protein-foldability>