Answer:
Yes, there will still be a chance for the F2 generation to have a ratio 9:3:3:1
Explanation:
According to Mendel's law of segregation, alleles of a gene pair separate at the time of game formation.
According to the Law of independence, the alleles sort independently into the gametes.
Even if the two traits under study are located on the same chromosome, they will segregate and assort independently at the time of gamete formation.
Also, at the time of meiosis, one of the alleles will arise from each parent hence there will still be a chance for the F2 generation to have a 9:3:3:1 ratio.
Crossing over and independent assortment depends on how distant genes are from each other. In the exposed example, if genes are not linked, the phenotypic ratio among the progeny is expected to be 9:3:3:1.
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⇒ Independent Assortment
Independent assortment law establishes that during gamete formation, the alleles from two or more different genes distribute independently from each other.
In other words, a gamete can receive alleles from different genes that do not depend nor influence each other during segregation.
Each gamete receives alleles that were randomly distributed.
Independent assortment law only applies to independent genes, not linked genes.
⇒ Independent Genes
These genes segregate independently after crossing over because they are located far away from each other in the same chromosome, or they are at different chromosomes.
⇒ Linked Genes
These genes are too close to each other in the same chromosome, that they do not segregate independently.
They are placed so close, that they can not distribute independently from each other, and they inherit together more frequently.
Crossing-over between linked genes that are very close to each other in the chromosome is not that common.
⇒ Crossing over events
Crossing-over during meiosis occurs randomly in different positions all along the chromosome.
Its occurrence frequency in the area between two genes depends on the distance between them.
A short distance between genes is a very little target for crossing-over to occur, which means that only a few of them will happen, compared with the number of events between genes that are more separated from each other.
There are few chances of crossing over and recombination events between two linked genes. These genes are strongly bounded.
⇒ Distances in Map Units
When the distance between genes is inferior to 50 Map Units, genes are considered to be linked, and they do not assort independently.
When the distance between two genes equals or exceeds 50 Map Units, genes are not linked and they distribute independently from each other.
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Would you expect an F2 generation of 9:3:3:1 for a dihybrid cross?
According to this framework, we could say that the probability of getting a phenotypic ratio 9:3:3:1 among the F2 depends on how distant genes are from each other.
We already know that they are placed in the same chromosome.
If the distance between them is inferior than 50 MU,
If the distance between them equals or exceeds 50 MU,
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