Is this an error in Destroyer?

[LetsGo2DSchool]

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The question and explanation says that the probability of crossing over occurring between two genes on a homologous chromosome is increased if they are farther apart.

I could've sworn I read in KBB or Cliffs AP Bio that it was the opposite -- the closer they are, the higher the chance. And logically this would make sense too.

Which is correct?

 

[bharat008]

The question and explanation says that the probability of crossing over occurring between two genes on a homologous chromosome is increased if they are farther apart.

I could've sworn I read in KBB or Cliffs AP Bio that it was the opposite -- the closer they are, the higher the chance. And logically this would make sense too.

Which is correct?

Destroyer is right. The farther away the genes are on the same chromosome the more chance that they would cross over in prophase 1.

 

[rockclock]

Destroyer is right. The farther away the genes are on the same chromosome the more chance that they would cross over in prophase 1.

+1. for crossing over to occur, you physically need to have a chiasma between those two loci...the more physical distance between them on the chromosome, the more potential locations for a crossing-over event to occur

 

[LetsGo2DSchool]

But isn't that counterintuitive. I mean if there's farther physical distance, then it should be more difficult to cross over... similar to me saying if two buildings were farther apart, I would have a greater chance of leaping from one and landing on the other?

 

[vicsin]

But isn't that counterintuitive. I mean if there's farther physical distance, then it should be more difficult to cross over... similar to me saying if two buildings were farther apart, I would have a greater chance of leaping from one and landing on the other?

It confused me too for that reason. But, it is definitely further apart. It is the opposite of what you'd logically think 👍.

 

[rockclock]

But isn't that counterintuitive. I mean if there's farther physical distance, then it should be more difficult to cross over... similar to me saying if two buildings were farther apart, I would have a greater chance of leaping from one and landing on the other?

that's not really an appropriate analogy for what's going on. it's actually not counter intuitive at all once you visualize it correctly.

we're not talking about how far apart the two chromosomes in the tetrad are, we're talking about how far apart the loci for the two genes in question are, measured along the same chromosome (this distance will be the same on the other homologous chromosome)

i.e. the gray bar, NOT the red/brown bar

a crossing over (chiasma) could occur anywhere on the chromosome along the gray bar for there to be a red gene/blue gene cross over. the longer that gray bar, the greater probability of it happening.

 

[LetsGo2DSchool]

I see. Thanks dude for the diagram.

 

[rockclock]

I see. Thanks dude for the diagram.

no prob. busted out a little Paint action...too bad they changed it up. classic Paint was a wonderful thing.

 

[blackhawk1986]

https://www.google.com/search?q=two...logy%2FPages%2FChapter11-Rabitoy.aspx;450;338

 

[Tajlrak]

that's not really an appropriate analogy for what's going on. it's actually not counter intuitive at all once you visualize it correctly.

we're not talking about how far apart the two chromosomes in the tetrad are, we're talking about how far apart the loci for the two genes in question are, measured along the same chromosome (this distance will be the same on the other homologous chromosome)

i.e. the gray bar, NOT the red/brown bar

a crossing over (chiasma) could occur anywhere on the chromosome along the gray bar for there to be a red gene/blue gene cross over. the longer that gray bar, the greater probability of it happening.

+1
It all fun and games until we break out the diagrams!

 

[Dotoday]

Destroyer is correct. You can only have recombination if the genes are far apart.

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