Gene Therapy and Regulation of Gene Expression Technological advances in the field of molecular biology in recent years have given us a more comprehensive understanding of the genetic material of living beings. This contains information that determines what we are. These advances have resulted in important achievements such as the description of the composition of the human genome.
Genetic recombination refers to the exchange between two DNA molecules. It results in new combinations of genes on the chromosome. You are probably most familiar with the recombination event known as crossing over.
In crossing over, two homologous chromosomes chromosomes that contain the same sequence of genes but can have different alleles break at corresponding points, switch fragments and rejoin. The result is two recombinant chromosomes. In bacteria, crossing over involves a chromosome segment entering the cell and aligning with its homologous segment on the bacterial chromosome.
The two break at corresponding point, switch fragments and rejoin. The result, as before, is two recombinant chromosomes and the bacteria can be called a recombinant cell. The recombinant pieces left outside the chromosome will eventually be degraded or lost in cell division.
But one question still remains The answer is Genetic Transfer! Genetic Transfer Genetic transfer is the mechanism by which DNA is transferred from a donar to a recipient.
Once donar DNA is inside the recipient, crossing over can occur. The result is a recombinant cell that has a genome different from either the donar or the recipient.
In bacteria genetic transfer can happen three ways: Transformation Transduction Conjugation Remember that a recombination event must occur after transfer in order that the change in the genome be heritable passed on to the next generation.
Transformation After death or cell lyses, some bacteria release their DNA into the environment. Other bacteria, generally of the same species, can come into contact with these fragments, take them up and incorporate them into their DNA by recombination.
This method of transfer is the process of transformation. Any DNA that is not integrated into he chromosome will be degraded. The genetically transformed cell is called a recombinant cell because it has a different genetic makeup than the donar and the recipient.
All of the descendants of the recombinant cell will be identical to it. In this way, recombination can give rise to genetic diversity in the population.
Griffith's Experiment The transformation process was first demonstrated in by Frederick Griffith. Griffith experimented on Streptococcus pneumoniae, a bacteria that causes pneumonia in mammals. When he examined colonies of the bacteria on petri plates, he could tell that there were two different strains.
The colonies of one strain appeared smooth.
Later analysis revealed that this strain has a polysaccharide capsule and is virulent, that it, it causes pneumonia. The colonies of the other strain appeared rough. This strain has no capsules and is avirulent. When Griffith injected living encapsulated cells into a mouse, the mouse died of pneumonia and the colonies of encapsulated cells were isolated from the blood of the mouse.
When living nonencapsulated cells were injected into a mouse, the mouse remained healthy and the colonies of nonencapsulated cells were isolated from the blood of the mouse.
Griffith then heat killed the encapsulated cells and injected them into a mouse. The mouse remained healthy and no colonies were isolated. The encapsulated cells lost the ability to cause the disease. However, a combination of heat-killed encapsulated cells and living nonencapsulated cells did cause pneumonia and colonies of living encapsulated cells were isolated from the mouse.
How can a combination of these two strains cause pneumonia when either strand alone does not cause the disease? If you guessed the process of transformation you are right!
The living nonencapsulated cells came into contact with DNA fragments of the dead capsulated cells. The genes that code for thr capsule entered some of the living cells and a crossing over event occurred. The recombinant cell now has the ability to form a capsule and cause pneumonia.Cheap dissertation writing services uk and ireland rigat essay ghirmay 28 weeks Gene therapy research paper notes Common app transfer essay super esl flow argumentative essay the meaning and purpose of education essay biological and biomedical sciences descriptive essay the diplomat documentary review essay les .
A harmful BRCA1 or BRCA2 mutation can be inherited from a person’s mother or father.
Each child of a parent who carries a mutation in one of these genes has a 50% chance (or 1 chance in 2) of inheriting the mutation. The effects of mutations in BRCA1 and BRCA2 are seen even when a person’s second copy of the gene is normal.
Phages P1 and P22 both belong to a phage group that shows generalized transduction (that is, they transfer virtually any gene of the host chromosome). During their cycles, P22 probably inserts into the host chromosome, whereas P1 remains free, like a large plasmid.
gene transfer mechanisms in microbes This is only a summary and you will need to add details from Chapter 10 o f Madigan, Martino and Parker, Brock, Biology of Microorganisms, 10th editon.
Questions pertaining to the efficiency of gene transfer and gene expression remain at the forefront of gene therapy research. Currently much debate in the field of gene therapy revolves around the transfer of desired genes to appropriate cells, and then obtaining sufficient levels .
Critical developments have occurred in gene therapy targeting cancer cells, cancer vasculature, the immune system, and the bone marrow, itself often the target for severe toxicity from therapeutic agents.
Possible mechanisms for the bystander effect include direct cell-cell drug transfer via gap junctions, immune-mediated responses such as.