Ribosomes

We can describes Ribosomes as workbench of biosynthesis. in general ribosomes are complex ribonucleoproteins particles made up of two subunits & each subunits contains RNA & proteins.
Ribosomes has the ability to catalyze the peptide bonds in both eukaryote & prokaryotes by placing sites for placing mRNA, tRNA & mRNA-tRNA complementary. 

Ribosomes are made up of two subunits, large subunit & small subunit & each subunit composed of multiple proteins & one or more than one RNA

Ribosomes source	Monomer size	Subunit
		Small	Large
Prokaryotes	70S	30S:       21 proteins 16S RNA	50S: 34 proteins 23S, 5S, RNA
Eukaryotes	80S	40S: 34 Proteins 18S RNA	60S: 50 proteins 28S, 5.8s, 5S RNA

you can notice in Prokaryotes, the ribosomes sedimentation is 70S, the whole ribosomes, the small subunits is 30S & the large subunit is 50S. some one may comes to his mined that 30S + 50S = 80S; SO why its 70S not 80S?
will the trick here that subunits are add by sedimentation not mathematically & this addition by sedimentation depends on the weight & mass.

Ribosomes are weighed in KD (kilodaltons). In Eukaryotes, 80S ribosomes are larger & more complex than prokarytoes. the 80S, the whole Ribosomes has a mass of 4200 KD, the small subunit 40S is 1400KD & the large subunit is 2800 KD

Recombination

the whole idea of recombination is to re-link; so we cut & re-link pieces of DNA within the chromosome; so there is exchange of pieces & these pieces contains information; so there is exchange of information among chromosomes.


chromosomes are pieces of nucleoproteins that contain DNA & contain genes in a linear array & genes are part of DNA in Chromosome.

recombination could be exchange of information among chromosome or sometimes within the same chromosome

lets sum up; recombination is a means by which a genome can change to generate new combinations of genes where as genome is the whole group of genes within an organism or within the cell.

there are 3 types of recombination:

1. transposition 
2. site specific recombination 
3. general or homologous recombination 

transposition 

we called them "Jumping genes"; meaning genes jump from site to site (they keep jumping); it enters, get integrated & then get released & then go else where
we could categories transposition into 2 subtypes (1) Replicative & (2) non-replicative

in replicative, if this transposition segment once it get integrated & then get released it leaves a copy of itself & then go else where
in non replicative; if this transposition segement it get integrated & then get released it doesn't leave any trace (almost no trace)

so transposons are short sequences can excise & reinsert itself at different place in the genome
transposition are short sequence of DNA inserted in the genome

the minimum requirements for any gene that has the capability to jump& reinsert itself are

• it should be flanked by 2 inverted reports 
• it should contain at least one enzyme called transposase that has capability to insert itself 

so it has a kind of ability to excised or double cut & ligase within the transposase (note in some transposon they have another enzyme called resolvase) 

site specific recombination 

requires a specific short DNA sequence (identical sequence)

Homologous recombination 

its requires a huge sequence of homology (it means resemble) 99% identical but not 100% identical