How to observe the bristles of fruit flies? The normal bristles and small bristles of fruit flies ar

Many of the traits we observe are qualitative traits (discontinuous traits), such as red-eye-white-eyed, long-winged, straight-bristle-scorched bristles, etc., which are either/or, there is no intermediate transition type, and many of the genetic traits studied in the laboratory belong to this type. However, many variations in nature, as well as many important traits in animal and plant breeding, are continuously varied, called quantitative traits such as height, growth rate, yield, etc., which exhibit a range of variation from one extreme to the other. Quantitative traits are strongly influenced by both genes and environment, and are often determined by polygenic interactions, with the role of each gene being small and equal.

The following experiments will illustrate how quantitative traits can be studied and how to distinguish between the roles of genetic and environmental factors in quantitative trait decisions.

This experiment involved two inbred lines of Drosophila, which showed large differences in the number of bristles on the ventral plates. The bristles on the ventral plate are composed of 2 or 3 long bristles and a row of small bristles (Fig. 8-1), usually because the male is smaller, the number of bristles on the ventral plate is also smaller, so in order to avoid errors caused by sex differences, only the bristles on the side plate of the same sex (usually female) can be counted in the experiment. Of course, if the number of fruit flies is large enough, both females and males can be counted.

First, catch a fly, then pluck the hair, and finally, observe it with an electron microscope.

First of all, you need the necessary equipment:

Several fruit flies. Microscope.

Several slides.

Glue. Tweezers.

Fix the flies on the slide with glue.

Kill fruit flies. Look at it with a microscope.

One thing to note: don't let fruit flies fly.

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1) Experimental idea: to determine whether the three pairs of genes are located on the three pairs of chromosomes, split into to determine whether each pair of genes is located on a pair of chromosomes, such as using and to carry out hybridization to determine whether a a and b b are located on a pair of chromosomes Experimental process: (to determine whether a a and b b are located on a pair of chromosomes as an example) Expected results and conclusions:

If the phenotype and proportion of F 2 is the presence of ocular normal bristles: there are ocular small bristles.

Hair: Eyeless normal bristles: Eyeless small bristles = 9:

3:3:1, then a a and b b are located on two pairs of chromosomes; Otherwise, a a and b b are located on the same pair of chromosomes (2) Experimental idea:

Verify that the two pairs of genes A A and B B are located on the X chromosome, and split them into verification that A A is located on the X chromosome and B B is on the X chromosome for verification respectively, such as using and Hybridization experiments to verify that A is on the X chromosome, and using and Hybridization experiments to verify that B B is on the X chromosome Experimental process: (Take the verification A A on the X chromosome as an example) Take the female and male for crossbreeding experiments: Expected results and conclusions:

If all females have eyes and all males have no eyes, a a is located on the X chromosome; If all the offspring have eyes, and the number of males and females is equal, then the A A position is balanced on the autosome, so the answer is: (1) Select three hybrid combinations, and obtain F 1 and F 2 respectively, if there are four phenotypes in F 2 of each hybrid combination, and the ratio is 9:3:

3:1, the three pairs of alleles can be determined.

Located on three pairs of chromosomes; If other results are present, it can be determined that the three pairs of alleles are not located on each of the three pairs of chromosomes (2) Select the hybrid combination for forward and negative crossing.

Observation of the phenotype of male individuals in F 1 If the male in orthogonal F 1 and the male in F 1 obtained by inbreeding have different relative traits in the male with eyes, no eyes, normal bristles, and small bristles, then it is proved that the two pairs of alleles are located on the X chromosome.

These traits are either/or, there is no intermediate transition type, and females can also be counted at the same time, and they show large differences in the number of bristles on the ventral plate, usually males have fewer bristles on the ventral plate because of their smaller size, if the number of flies counted is large enough. However, there are many variations in nature, and these traits exhibit a range of variation, growth rates, from one extreme to the other. Quantitative traits are strongly influenced by both genes and environment, and are usually determined by polygenic interactions, with each gene acting in small and equal amounts, so to avoid errors due to sex differences, only the bristles on the side plates of individuals of the same sex (usually female) can be counted in the experiment.

Of course. The bristles on the ventral plate are composed of 2 3 long bristles and a row of small bristles (Figure 8-1), yield, etc., as well as many important traits in animal and plant breeding are all varied continuously, called quantitative traits.

Two inbred lines of Drosophila were involved in this experiment. The following experiments will illustrate how quantitative traits can be studied, and how to distinguish between the role of genetic and environmental factors in the determination of quantitative traitsMany of the traits we observe are qualitative traits (discontinuous traits), such as red-white eyes, long-winged-small wings, straight bristles-focal bristles, etc., many of the genetic traits studied in the laboratory belong to this type, males, such as height.