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Lecture 6. altered genes are mutations

The DNA sequences from two individuals of the same species are highly similar - differing by only about one nucleotide in 1,000. A mutation is, most simply, an alteration in a DNA sequence.  This change may or may not lead to a change in the protein coded by the gene.  A change that has no effect on protein sequence or function is termed a polymorphism and is a part of the normal variation present in the human genome.  Often, however, a change in a DNA sequence will result in the disruption of gene function that we term "Clinical Manifestations" in the Clinical Integration Model .  The altered protein that results from a mutation can disrupt the way a gene functions, and this can lead to clinical disease.  How these mutations manifest themselves depends on each individual's unique genetic endowment and interactions with their environment. 

Furthermore, the change may or may not be passed on to subsequent generations.  If, as in non-familial cancer, the mutation occurs in isolated somatic cells , it will not be passed on to subsequent generations.  Only those mutations occurring to the DNA in the gametes (egg or sperm) will potentially be passed on to offspring.  If the mutation is passed on to the offspring, they will carry this mutation in all of the cells in their body.  

Following is a brief review of different types of mutations:

Base pair substitution

Replacement of one DNA base by another in the DNA sequence. Replacement of nucleotide bases can have several possible consequences.

Missense mutation

An amino acid residue in the original protein may be replaced by a different one in the mutated protein.

Nonsense mutation

The codon for an amino acid residue within the original protein is changed to a stop codon, which leads to a premature termination of the protein resulting in a non functional protein.

Silent mutation

  The codon for an amino acid is changed, but the same amino acid is still coded for.  This is possible because some amino acids are coded for by multiple codons.  For example, the sequences UGC and UGU both code for Cysteine.

Frameshift mutation

A deletion or insertion of any number of bases other than a multiple of three bases has a much more profound effect. Such frameshift mutation results in a complete change in the amino acid sequence downstream from the point of mutation, instead of simply a change in the number of amino acids.  

Deletions, insertions, and duplications

Deletions or insertions may be large or small. Large insertions and deletions in coding regions almost invariably prevent the production of useful proteins. The effect of short deletions or insertions depends on whether or not they involve multiples of three bases. If one, two, or more whole codons (three base pairs or any multiple of three) are removed or added, the consequence is the deletion or addition of a corresponding number of amino acid residues.  Sometimes, an entire gene can be inserted (duplicated) or deleted.  The effects of these types of mutations depend on where in the genome they occur and how many base pairs are involved.  

Questions & Answers

what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
how can I make nanorobot?
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
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Source:  OpenStax, Genetics. OpenStax CNX. Jul 29, 2009 Download for free at http://cnx.org/content/col10782/1.1
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