Di Truyền theo dòng mẹ

Cytoplasmic male sterility
Teacher: Đỗ Lê Thăng
Student : Đỗ Thị Nhuân
Interaction between nuclear and cytoplasmicgenes
12 : 3 : 1 và 13:3
9 : 3 : 4
9 : 3 : 3 : 1
9 : 6 : 1
Cytoplasmic male sterility (CMS) in maize

•Observed by Marcus Rhoades in 1933.
•Maize has both male (tassel) and female Inflorescence (cob).
•CMS plants fail to produce viable pollen in tassels, but are fertile as females.
•Used in agriculture to generate hybrids with desirable characters.
Interaction between nuclear and cytoplasmicgenes
Mitochondrial DNA
•Predominantly maternally inherited in plants and animals
•Haploid (one copy in each individual)
•No recombination
•Crossing CMS plants to male fertile plants for many generations does not produce male fertility.
•CMS results from a mutation in a mitochondrial gene whose function is vital for pollen maturation.

Interaction between nuclear and cytoplasmicgenes
•In certain crosses involving CMS plants, male fertility can be restored by alleles of two nuclear genes known as restorer or fertility genes (Rf1 and Rf2)
•Dominant alleles at both Rf1 and Rf2 are necessary to restore fertility.
mtDNA and Male Fertility
Sperm are motile and powered by mitochondria , even small reduction in power may reduce sperm mobility and reduce fertility
Maternally inherited cytoplasmicfactors (Maternal Effect)


Produce inheritance patterns strictly dependent on the genotype of the mother, known as maternal effects.
• Phenotype does not depend on the genotype of the individual or genotype of the father.
- Example:
Coiling in the snail Limneaperegra
The direction of shell coiling is controlled by a single gene.
The phenotype of an individual is determined by the genotype of its mother.
Right (dextral) coiling (D) is dominant to left (sinistral) coiling (d)
The genotype of a mother determines the structure of the eggs that she produces.


- Diagram
Maternal effect is not the same as cytoplasmic inheritance

Maternal effect -causes an individual’s phenotype to be determined by gene products inherited in the egg cytoplasm.

Cytoplasmic inheritance is controlled by the genes in the cytoplasm.

The genetics of infectious agents


Teacher :PGS TS Đỗ Lê Thăng
student:Nguyễn Trần Bích Diệp
symbiotic bacteria
Virut (HIV)
Viroid and prion

Introduction

1,Symbiotic bacteria
Kappa in Paramecium
Introducetion of kappa seed
There are two strains of Paramecium. They are killer and sensitive. Killer strain produces a toxic substances called paramecin that kills the other type. The production of paramecin in killer type is controlled by certain cytoplasmic particles known as kappa particles.
The kappa particles pass from one generation to the next generation in the process of cell division. The kappa particles are also multiplied with cell division. They are transmitted through the cytoplasm
Conjuction without cytoplasmic
exchage and Conjuction with
cytoplasmic exchange

During this cytoplasmic exchange, the kappa particles present in the cytoplasm of the killer type enter the non-killer type and convert it into a killer type.
So all the offspring produced by the exconjugants are killer type.
This shows that a Paramecium becomes a killer when it receives kappa particles and it becomes a sensitive when it does not receive kappa particles.



2,infectious heredity in viruts





How is HIV transmitted from mother to child?


Without intervention, between 25% and 35% of the children born to HIV-positive mothers will themselves be infected.
In about 50% of the cases, transmission from mother to child occurs during labor and delivery


Scientists don`t yet understand how exactly that transmission happens, but they have found that some treatments can prevent most cases.
However, to many HIV-positive pregnant women in developing countries, these treatments are not available or acceptable.
The hope is that better understanding of mother-to-child transmission will lead to more effective, more affordable, and more acceptable treatments.
3. viroid and pirion
a.viroid:
Infectious agent that is smaller than any of the known viruses. The agent consists of an extremely small circular RNA molecule that lacks the protein coat of a virus.
Viroids mainly cause plant diseases but have recently been reported to cause a human disease.
Summary


Viroids appear to be transmitted mechanically from one cell to another through cellular debris. They are of much interest because of their subviral nature and their unknown mode of action.


b,Prion:is an infectious agent that is composed primarily
of protein.They contain no nucleic acid



In prion disease there is a long incubation period before one sees loss of muscle coordination,dementia and progressive insomnia.
   Prions induce no immune reactions within the human.
Kuru is an incurable degenerative neurological disorder (brain disease).Kuru is found in humans.
the infection rates—kuru in women and children bigger than in men because while the men of the village took the choice cuts, the women and children would eat the rest of the body including the brain, where the prion particles were particularly concentrated.
There is also the strong possibility that it was passed on to women and children more easily because they took on the task of cleaning relatives after death and may have had open sores and cuts on their hands


Thank you very much