1. What differences would you exepct to see in a population made up of individuals whose chromosomes experince crossing-over frequently compared with a population made up of individuals whose chromosomes do not cross over? Why?
2007-01-10 08:23:53 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Biology
In the population with individuals whose chromosomes do not cross over, you'll find "linked traits" -- traits that are always inherited together.
Suppose "vermilion eyes" and "wing halteres" were on the same chromosome (and I don't know if they are, so don't quote me). In a population in which there was no crossing over, if you found an individual with vermilion eyes and wing halteres it would be a safe bet that most individuals with vermilion eyes would also have wing halteres. Similarly, most individuals with wing halteres would also have vermilion eyes.
Crossing over increases the likelihood that those alleles can separate from each other. With crossing over, you would find individuals with one of the characteristics but not the other.
I haven't explained this well. I hope someone comes and explains it better.
2007-01-10 09:07:48 · answer #1 · answered by Anonymous · 1⤊ 0⤋
Do you remember when you learned about Mendel's experiments, you learned that genes segregate independently? He did dihybrid crosses and got an 9:3:3:1 ratio for F1 cross? Well, Mendel was lucky that he chose genes that were on separate chromosomes. If the genes he was looking at were on the same chromosomes, the alleles would not have segregated independently, and would not get the 9:3:3:1 ratio.
What Mendel saw will not happen with genes that are linked (genes on the same chromosomes--usually close to each other). If the genes are linked, certain characteristics will always tend to go with another. An example of this is a gene that gives some dogs white coats and deafness. Many dogs that are born deaf are white. This is because these genes are linked.
Only way for a linked gene to segregate is by crossing over. This is when homologous chromosomes swap genes during prophase I of meiosis.
So the simple answer is: in a population with low occurance of crossing over, there will be higher occurances of linked traits. In a population with more crossing over, there will be more mixing of alleles and it would appear that the genes segregate randomly.
By the way, this is how they used to map genes on a chromosomes-- look at the occurances of cross-overs. I think they did this with fruit flies.
2007-01-10 17:16:38 · answer #2 · answered by Ms. K. 3 · 0⤊ 0⤋
from one student to another.
Crossing over with the same chromosomes should create genetic diseases and mutated genes.
Without crossing over, the population will not be mutated.
As in dogs and cats, if you breed purebloods for a long time (a hundred generations) the breed will start to dry out and you will be breeding siblings together.
2007-01-10 16:36:19 · answer #3 · answered by Anonymous · 0⤊ 0⤋
well, asexual reproduction for one.
2007-01-10 16:36:25 · answer #4 · answered by John W 1 · 0⤊ 0⤋