The plant Haplopappus gracilis has a 2n of 4. A diploid cellculture was established and, at premitotic S phase, aradioactive nucleotide was added and was incorporatedinto newly synthesized DNA. The cells were then removed from the radioactivity, washed, and allowed to proceed through mitosis. Radioactive chromosomes or chromatids can be detected by placing photographic emulsionon the cells; radioactive chromosomes or chromatids appeared covered with spots of silver from the emulsion.(The chromosomes “take their own photograph.”) Drawthe chromosomes at prophase and telophase of the firstand second mitotic divisions after the radioactive treatment. If they are radioactive, show it in your diagram. Ifthere are several possibilities, show them, too.
Genetic Variation
Genetic variation refers to the variation in the genome sequences between individual organisms of a species. Individual differences or population differences can both be referred to as genetic variations. It is primarily caused by mutation, but other factors such as genetic drift and sexual reproduction also play a major role.
Quantitative Genetics
Quantitative genetics is the part of genetics that deals with the continuous trait, where the expression of various genes influences the phenotypes. Thus genes are expressed together to produce a trait with continuous variability. This is unlike the classical traits or qualitative traits, where each trait is controlled by the expression of a single or very few genes to produce a discontinuous variation.
The plant Haplopappus gracilis has a 2n of 4. A diploid cell
culture was established and, at premitotic S phase, a
radioactive
into newly synthesized DNA. The cells were then removed from the radioactivity, washed, and allowed to proceed through mitosis. Radioactive chromosomes or chromatids can be detected by placing photographic emulsion
on the cells; radioactive chromosomes or chromatids appeared covered with spots of silver from the emulsion.
(The chromosomes “take their own photograph.”) Draw
the chromosomes at prophase and telophase of the first
and second mitotic divisions after the radioactive treatment. If they are radioactive, show it in your diagram. If
there are several possibilities, show them, too.
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