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There are two kinds of tetrads in fungi: ordered and unordered tetrads. Ordered tetrads contain the spores (the products of a single meiosis) inside the sac (ascus) in a linear order according to the moving behaviour of chromosomes in meiosis. The tetrads of the kind are available in Neurospora crasa, for example. Unordered tetrads contain the spores inside the ascus in a disorder without any sequence, which are available, for example, in Saccharomyces cerevisiae. Genetic analysis of ordered tetrads technically give more information than that of unordered tetrads. A demonstration of genetic analysis in ordered tetrads is given in MITOPENCOURSEWARE ( PDF ).

Lecture 28. human dna polymorphisms

One of the most important tools underlying the revolution in medical genetics is the ability to visualize sequence differences directly in DNA. When studied in the context of a population, these differences in DNA sequences are called polymorphisms; they may occur in coding regions (exons) or noncoding regions of genes. The ability to visualize thousands of DNA polymorphisms has made possible family studies for tracking genes of medical importance. This technique has located and identified genes for many disorders with a clear pattern of mendelian inheritance, such as cystic fibrosis, the inherited muscular dystrophies, and neurodegenerative disorders such as Huntington's disease. Methods that exploit genetic polymorphism will also be essential for finding genes that predispose people to more common conditions in which inheritance patterns are complex, such as diabetes, atherosclerosis, and hypertension.

DNA polymorphisms are also playing a crucial part in unraveling the genetic basis of tumor formation and progression in cancer. They provide markers for the loss of specific chromosomal segments during the evolution of a tumor. DNA polymorphisms have already been crucial in the identification of genes important for susceptibility to common forms of cancer, such as colon cancer, as well as susceptibility to less common childhood tumors, such as retinoblastoma and Wilms' tumor.

The most useful DNA sequence polymorphisms have many alternative forms. The value of highly variable DNA sequences as genetic markers rests on straightforward principles. Every person carries two copies of each chromosome except the sex chromosomes. If a DNA polymorphism is to be useful in analyzing the transmission of the two chromosomes in a family or the loss of one of the chromosomes during tumorigenesis, then the DNA copies at the polymorphic site of the person under study must be different in the two chromosomes ( Figure 1A ), Figure 1B ), Figure 1C ), and Figure 1D ). The likelihood that a given person will have different DNA sequences at the polymorphic site directly determines the usefulness of that site in genetic studies. Chromosomal sites at which the DNA sequences can have many alternative forms are thus ideal sites for genetic markers. At these sites, a person is most likely to carry two alternative DNA sequences, accurately marking the two alternative chromosomes.

Questions & Answers

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
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
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.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
On having this app for quite a bit time, Haven't realised there's a chat room in it.
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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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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