What is linkage strength between gene loci?

[Tyto alba]

Homework Statement

In linkage strength between any two gene loci is 70%,what would be the amount of crossing over between
these loci?

(a) 15% (b)30% (c) 70% (d) none of these.

2. My approach at understanding the concept

I didn't find much about linkage strength from any authentic source.
I can think of two things :

• The strength of a linkage would be greater if the spatial separation between two genes is less and the lesser if the separation is more. This is semantic. But,
  
• how can it be represented in percentage? What does this 100 mean in this 70%? The separation between two genes can be more than 100 map units.

3. Question in details

What does linkage strength mean? How is it related to amount of crossing over?

I would appreciate answers citing some authentic sources.

 

[epenguin]

Homework Statement

In linkage strength between any two gene loci is 70%,what would be the amount of crossing over between
these loci?

(a) 15% (b)30% (c) 70% (d) none of these.

2. My approach at understanding the concept

I didn't find much about linkage strength from any authentic source.
I can think of two things :

• The strength of a linkage would be greater if the spatial separation between two genes is less and the lesser if the separation is more. This is semantic. But,
  
• how can it be represented in percentage? What does this 100 mean in this 70%? The separation between two genes can be more than 100 map units.

3. Question in details

What does linkage strength mean? How is it related to amount of crossing over?

I would appreciate answers citing some authentic sources.

I suppose an authentic source would be the 600+ page 'Dictionary of Genetics'. It is not mentioned there. I have never heard the term used In a technical defined way; I suppose it can be used in a loose way io speaking. I do not understand how you can be asked such a question and are not supplied with a text that gives you a definition. I think genetic distances are usually expressed in centimorgans.

I would just answer 30% and wait to see if your Prof. gives an explanation.

 

[Tyto alba]

I think it is not a standard term too, if so Google would have shown some results. It was in a question paper, not a homework.

I also thought that way.
But using the word linkage strength to mean amount (proportion) of offspring with parental combination of genes is a bit strange.

 

[epenguin]

One usually hears of closeness of linkage rather than strength.