Dunaliella salina - Overview

-
Image
                 Dunaliella salina Dunaliella salina is a unicellular microalgae belong to division Chlorophyta . It is found in salinity environments such as salted brines, salt evaporation ponds, and hypersaline lakes  .It is able to tolerate varying NaCl concentrations, ranging from 0.2% to approximately 35% . Thus, Dunaliella salina is a hyper-halotolerant organism found in high densities in saline lakes.  The ability to tolerate high salt concentrations is advantageous, since competition is minimal in high salt concentration areas.  How D.salina   tolerate high salt concentration? D. salina has adapted to survive in high salinity environments by accumulating glycerol to balance osmotic pressure. Note :  D. salina is also adapted to solar radiation using β-carotene to protect against ionizing energy.                 Red Colour of Salt Brines  Dunaliella salina...
Post a Comment

Pleiotropy,polygenic inheritance,lethal genes

-

Pleiotropy: Tendency of gene to produce multiple phenotypic effect.
**When a gene control more than one character.This phenomenon is called pleiotropy.Such genes are called pleiotropic genes.
**In case of more than one character controlled by a single gene,all the characters are not equally influenced i.e.one character may show dominance,whereas another character may show incomplete dominance, codominance or dominance.Therefore,    dominance is not an autonomous feature of a gene oe its product,it is also dependent on interaction or effect of the product of that gene on a particular character.
**Example:Starch branching enzyme gene(control size of starch grain and shape of grain),phenylketonuria(control synthesis of phenylalanine hydroxylase enzyme,  depigmentation,mental retardation,hair loss,arthritic joints),Heterozygous for sickle cell anaemia(shape of RBC,resistant for malaria),White eye mutant (eye colour,wing size,pigmentation of body).


Polygenic inheritance:Single character is controlled by more than one gene.All the genes controlling a particular character  called polygenes.Reported by Nilson-Ehle in 1908 and East  in 1910.
**Show  additive or polymeric effect of all the dominant alleles.Due to additive effect,the trait is observed along a gradient.
**Intensity  of the trait is directly proportional to the number of dominant   alleles.
**Number of phenotypes: 2n+1
where n is number of pair of polygenes.
**Number of genotypes: 3n(n in the form of power;) where n is number of heterozygous pair.For example if n is 2 then no.of genotyoes is 9(n in the power)
**Examples:
KERNEL COLOUR IN WHEAT-by Nilson Ehle--
controlled by 2 pair of polygenes
A and B=Red colour
a and b =White colour
Number of phenotypes=2n+1 =5(n is 2)
Number of phenotypes=3n(n in power)=9

HUMAN SKIN COLOUR-by C.V.Deveripest
controlled by 3 pair of polygenes
A,B,C - synthesis of melanin pigment (darkness;negro in africa)
a,b,c - non synthesis of melanin
Number of phenotype=2n+1=7
Number of genotypes=3n(n in power)=27


Lethal Genes: The genes which cause death of organism.3 types:
1)Absolute lethal genes: death in foetal stage;in uterus.
2)Semi-Lethal: death in reproductive stage.
3)Delayed lethal:death in after reproductive age.
**If lethal genes are recessive then eliminate but if the lethal genes are dominant then never eliminate.
Example - Coat colour in mice
Yy-  yellow
YY-  yellow
yy-    black

                         Male   ×  Female
    Parents:         Yy       ×   Yy
    Gametes:     Y,  y            .Y,  y

F1 progeny :          YY   ,  Yy  ,   Yy  ,  yy 

phenotypic ratio:     Yellow  : black
                                       2      :  1
 3:1  changes into 2:1 because YY is absolute lethal condition.Hence,one died.
Parents with YY genotype doesn't possible because organism of this genotype died in uterus.


Comments

Post a Comment

Popular posts from this blog

Parthenogenesis

-
    Parthenogenesis * Mode of reproduction in which the female gamete develops into embryo without any genetic contribution from the male gamete is called parthenogenesis. * The individual formed from parthenogenesis is called parthenot. *It is also called virgin birth. * It is always monoparental. *Term parthenogenesis is coined by Richar Owen .                            Occurence  Parthenogenesis occur uncertain orders of  insecta: Hymenoptera, Coleoptera ,Homoptera,Rotifera and lower crustaceans .It is also reported in certain vertebrates; in domestic turkey.It occurs sporadically in large number of plants .               Types of parthenogenesis Two types: 1)Natural parthenogenesis 2) Artificial parthenogenesis                                Natural  First reported by Bonnet...
Read more

Dunaliella salina - Overview

-
Image
                 Dunaliella salina Dunaliella salina is a unicellular microalgae belong to division Chlorophyta . It is found in salinity environments such as salted brines, salt evaporation ponds, and hypersaline lakes  .It is able to tolerate varying NaCl concentrations, ranging from 0.2% to approximately 35% . Thus, Dunaliella salina is a hyper-halotolerant organism found in high densities in saline lakes.  The ability to tolerate high salt concentrations is advantageous, since competition is minimal in high salt concentration areas.  How D.salina   tolerate high salt concentration? D. salina has adapted to survive in high salinity environments by accumulating glycerol to balance osmotic pressure. Note :  D. salina is also adapted to solar radiation using β-carotene to protect against ionizing energy.                 Red Colour of Salt Brines  Dunaliella salina...
Read more