Question: Genetic Distance Between Genes On Different Chromosomes
3
gravatar for Spandankeshav
8.3 years ago by
Spandankeshav160
Turku, Finland
Spandankeshav160 wrote:

If two genes are in different chromosomes then how can we measure the distances between them?

gene genetics distance chromosome • 5.3k views
ADD COMMENTlink modified 8.3 years ago by Giovanni M Dall'Olio26k • written 8.3 years ago by Spandankeshav160

What do you mean with '''distance''' ? a recombinant frequency (cM ) ?

ADD REPLYlink written 8.3 years ago by Pierre Lindenbaum118k

He could mean the physical distance (measured in micrometers or some suitably small unit). That would vary over the life of the cell.

ADD REPLYlink written 8.3 years ago by David Quigley11k

He could mean physical distance, e.g. measured in microns rather than base pairs. That would vary over the life of the cell.

ADD REPLYlink written 8.3 years ago by David Quigley11k

Yeah Pierre you are right. I mean recombinant frequency (cM).

ADD REPLYlink written 8.3 years ago by Spandankeshav160

changed the title. Come on, try to think of a better title when posting here.

ADD REPLYlink written 8.3 years ago by Giovanni M Dall'Olio26k
13
gravatar for Casey Bergman
8.3 years ago by
Casey Bergman18k
Athens, GA, USA
Casey Bergman18k wrote:

The "recombination" frequency of two independent linkage groups (chromosomes) is defined as 0.5 because of Mendel's Second Law of Independent Assortment.

From wikipedia: "any alleles that are completely unlinked (e.g. alleles on separate chromosomes) have a 50% chance of recombination, due to independent assortment."

A recombination frequency of 0.5 implies two genes are "unlinked," regardless of whether they are on the same or different chromosomes.

ADD COMMENTlink written 8.3 years ago by Casey Bergman18k
5
gravatar for Giovanni M Dall'Olio
8.3 years ago by
London, UK
Giovanni M Dall'Olio26k wrote:

You calculate it in the same way as you do for genes on the same chromosome. If two genes are in linkage disequilibrium even in this condition, it may mean that they are involved in the same function. Note that you don't need to know whether two genes are on the same chromosome to calculate their genetic distance; in fact, Morgan's student Sturtevant did not even know the concept of chromosome when he coined the definition.

ADD COMMENTlink written 8.3 years ago by Giovanni M Dall'Olio26k

"If two genes are in linkage disequilibrium even in this condition, it may mean that they are involved in the same function" could you please cite the source from where you got this information ? just for reading up

ADD REPLYlink written 8.3 years ago by Sudeep1.6k

it just comes from the definition of Linkage Disequilibrium http://en.wikipedia.org/wiki/Linkage_disequilibrium . If two alleles of different genes on different chromosomes tend to be inherited together with a frequency different that what expected, it may be because they are associate with the same function and having the two alleles together gives some sort of positive advantage to the individuals. Of course, it may simply be the result of drift or hitch-hiking.

ADD REPLYlink written 8.2 years ago by Giovanni M Dall'Olio26k
2
gravatar for Pierre Lindenbaum
8.3 years ago by
France/Nantes/Institut du Thorax - INSERM UMR1087
Pierre Lindenbaum118k wrote:

aside from the Chromosomal abnormalities there is no recombination/crossing over between two non-homologous chromosomes, so the genetic distance has no meaning here.

ADD COMMENTlink written 8.3 years ago by Pierre Lindenbaum118k
2

it makes sense to calculate genetic distance between genes on different chromosomes, because if two genes are in linkage disequilibrium even in this condition, it may mean that they are involved in the same function.

ADD REPLYlink written 8.3 years ago by Giovanni M Dall'Olio26k

thanks for the clarification Giovanni

ADD REPLYlink written 8.3 years ago by Pierre Lindenbaum118k
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