DNA recombinant

2.  Exchange of genetic information
 Types :-
- Homologous genetic recombination
- Site specific recombination
- DNA transposition

3.  Maintenance of genetic diversity .
 Specialized DNA repair system
 Regulate of expression of certain genes.
 Programmed genetic rearrangements
during development.

5.  Occur between identical chromosomes .
- eg;- paternal & maternal chromosomal pairs
 Is k/a Holliday model.
 Features :-
- Alignment of homologous DNAs.
- One strand of the each DNA is broken &
joined to the other to form crossover
structure is k/a Holliday intermediate.

6.  The region in which strands from
different DNA molecules are paired is
k/a heteroduplex DNA ,is extended by
branch migration .
 Two strands of Holliday intermediate
are cleaved & breaks are repaired to
form recombinant product.

7.  Exchanges occur only at defined sequence
 Found in virutally all cells but their
functions are different in species to
species .
 Consists of an enzyme recombinase &
short unique DNA sequence (recombinant
site).

8.  Non –homologous recombinant
 Not required special homologous sequcence
 Are segments of DNA
 It moves form one location to another
location of same chromosome or different
 Found in all cells , mainly in eukaryotes.
 Retro-transposons are similar to
transposons that they involve an RNA
intermediate

10.  Viral DNA polymerase is k/a Reverse
transcriptase.
 Uses RNA as template to synthesize DNA.
 RNA dependent DNA polymerase.
 Some viruses as retroviruses carry RNA as their
genetic material .
 Synthesized double stranded DNA from RNA is
k/a Reverse transcription .
 Eg:- human immunodeficiency virus (HIV)
- Causes AIDS.

12.  Polymer of purine and Pyrimidine
ribonucleotides linked together by 3′,5′-
phosphodiester bridges.
 The sugar to which the phosphates, purine
and Pyrimidine bases are attached is ribose
rather than the 2′-deoxyribose of DNA.
 RNA contains the Pyrimidine uracil in place of
thymine of DNA.

13.  A =adenine
 U =uracil
 C = cytosine
 G =Guanine
 codes for protein
 no consistent secondary
structure
 single stranded
 Ribose instead of
deoxyribose
 Thymine (T) replaced by
Uracil

14.  RNA exists as a single strand, whereas DNA
exists as a double-stranded helical molecule.
 Single strand of RNA—is capable of folding
back on itself like a hairpin and acquiring
double stranded structure.
 Does not obeyed Chargaff's rule, due to
presence of sRNA .
-A + G = U + C

15.  Three types :-
 Messenger RNA (mRNA) :-
- template for protein synthesis
 Transfer RNA (tRNA):-
- adaptor molecules that decode the genetic
code
 Ribosomal RNA:-
- catalyzing the synthesis of proteins

16.  Nucleus contains special type of RNA that
turns over rapidly during protein synthesis .
 Consists of mixture of very long RNA
molecules .
 Much longer than m-RNA .
 Are precursors of mRNA
 Modified by attachment of poly A tail &
methylguanosine cap.

17.  Synthesized in the nucleus as heterogeneous
nuclear RNA (hnRNA).
 Its functional mRNA , enter into cytoplasm to
participate in protein synthesis.
 Structure of mRNA :-
 In eukaryotes mRNA :- 5’ end of mRNA is
capped by 7-methylguanosine triphosphate .
 Cap is involved in the recognition of mRNA by
the translating machinery .
 Prevent from attack of 5’ exonucleases .

18. Other 3’end attached with poly A “tail” .
Consists of 20-250 adenylate residues
joined by 3’ to 5’ phosphodiester bonds.
Maintain the intracellular stability of
mRNA .
Preventing from attack of 3’
exonuclease.

19. 5’ 3’
7’methylguanosine PolyA tail Poly A tail
triphosphate
CAP

20.  vary in length from 74 to 95 nucleotides.
 serve as adapters for the translation of
the information
 Function :- carries amino acids in an
activated form to the ribosome for the
translations of the information in the
sequence of nucleotides of the m-RNA.

21.  Structure :-like clover leaf
 Made up of four arms :-
 Acceptor arm:- consists of base paired stem at
3’ end CCA seq. (5’ 3’)
 D arm :- presence of the base dihydrouridine
base.
 Anticodon arm:- contain anticodon that base
pair with the codon on m-RNA.
 TᵠC arm :- contains both ribothymidine &
pseudouridine ᵠ .
 Variable arm :- varies in size .

23. Machinery for synthesis of protein from the m-
RNA.
Composed of large & small subunit.
Prokaryotic & eukaryotic cells having
sedimentation coefficients of 70S & 80S resp.
Function :- participates in protein synthesis.
- Also have catalytic activities .

25.  Enzyme contain RNA component is
ribonuclease P.
 Cleave RNA phosphodiester bonds
 Contain protein & RNA component.
 Catalyzes the maturation of tRNA by removing
nucleotides from 5’ end of precursor tRNA .
 RNA components of ribosome have
ribonucleases & peptidyl transferase activity
carries out protein synthesis.
 Involves in the formation of peptide bonds in
protein synthesis.

26.  Considered as therapeutic agents
for disorders that caused by
expression of the mutated RNA .