You have two parents (1)fast-growing vines with weak stalks, and (2) slow-growing vines with strong stalks.
You cross the two pure-breeding vines but obtain only slow-growing plants with weak stalks. You then self-cross the F1 vines a number of times, but obtain only the F0 or F1 phenotypes, never the fast-growing, strong plants that are desired.
Are the genes that control stalk strength and growth rate on the same or separate chromosomes?
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I thought they were on the same chromosome but are really close to each other, so no crossing over can occur thus the fast and strong plant phenotype is not exhibited. and then that means that the dominant alleles are weak stalks and slow growing vines.
Do I have this right or am I on the wrong path?
Thanks
You are on the right path! Based on the information provided, you can infer that the genes that control stalk strength and growth rate are located on the same chromosome and are closely linked. Let me explain in more detail.
In genetics, genes are located on structures called chromosomes. Each chromosome can carry multiple genes. During the process of sexual reproduction, chromosomes are inherited from the parents to the offspring.
In this case, you have two pure-breeding vines: one with fast-growing vines and weak stalks, and the other with slow-growing vines and strong stalks. When you cross these two pure-breeding vines, you obtain slow-growing plants with weak stalks, indicating that the alleles for slow growth and weak stalks are dominant over the alleles for fast growth and strong stalks.
Next, you self-cross the F1 vines, which means that you take the offspring from the first generation and cross them with each other. If the genes controlling stalk strength and growth rate were on separate chromosomes, during the self-crossing, crossing over (a process of genetic recombination) could occur between the two chromosomes, leading to the possibility of obtaining different phenotypes including fast-growing, strong plants.
However, in this case, you mentioned that you only obtained the F0 (first generation) or F1 (second generation) phenotypes, and never the fast-growing, strong plants that were desired. This suggests that the genes controlling stalk strength and growth rate are closely linked on the same chromosome and are not easily separated through crossing over.
Therefore, your conclusion that the dominant alleles for weak stalks and slow growth are on the same chromosome and closely linked is correct. The lack of recombination between these genes prevents the expression of the fast-growing, strong plant phenotype.