Chain exchange of genes and gene positioning (table)

, the purpose of the experimentTo observe the chain genetic phenomenon between corn grain characteristics, to understand the principle of chaining and exchange, and to master the method of determining the exchange value
between
genes and gene positioning., experimental principletwo non-alleles (such as AB or ab) located on the same chromosome are always associated with a tendency to be distributed in the same match. If the two non-allethic genes are completely interlocked, the hybrid body (AB//ab) produces only 2 parent-type matching sons (AB and ab), and the F2 generation appears to have the same 2 esoteric types as the hybrid parent. If the two non-isometogene genes are not fully interlocked, the he throosome (AB//ab) still produces 4 types of ligands, but their ratio is not 1:1:1:1, and always parent-type matching (AB and ab) is the majority, recombination Type matchings (Ab and aB) are in the minority, and there are 4 watches in the F2 generation, but the ratio does not match 9:3:3:1, but the ratio of parent watches is large and the proportion of recombinant watches is small. This genetic phenomenon is called chain genetics.The hybrids of two incompletely interlocking non-alleles produce four numbers of different ligands because: between a pair of non-alleles on a zoogenous chromosome, the exchange usually occurs during the division of the number of detracts, resulting in gene recombination, exchange and the recombination of a spore (sex) ) The parent cells form 4 equally proportioned matching children (parental rations AB and ab and recombined matching sons Ab and aB), while no exchange or exchange occurs at the bit but does not lead to gene recombination of spore (sex) parent cells form only 2 parent-type matching sons (AB and ab). Therefore, in the interlocking genetics of the two personalities, only a small number of recombined individuals appear in the hybrid offspring. Probability P (0≤P≤50%) of recombinative individuals in hybrid offspring groups depends on the probability of exchange between two pairs of genes, generally expressed in recombination values (Rf) (the number of recombinative matchos produced by F1 generation spores/sex parent cells as a percentage of the total number of pairs). There are often two methods of recombination of recombination values: the method of measurement and the method of self-delivery (F2). General corn and other exotic pollinators and animals, more use of cross-dating to determine recombinant values, and wheat, rice and other self-pollination crops, due to the workload of cross-pollination method is too large, commonly used self-intersection method.According to chromosomal-gene theory, genes are linearly arranged on chromosomes in a certain order and distance, and the chance of forming a recombined ligand due to fracture and exchange between adjacent gene bits is positively related to the distance between the two, i.e. the greater the distance, the greater the chance of fracture and exchange producing a recombined ligand. Therefore, the size of the relative distance between the two genes can be reflected in the exchange rate. The specified exchange rate of 1% is called a genetic graph distance (1cM s 1Mbp), and the relative distance between the two genes (genetic distance) is expressed by the exchange rate of the two genes. The smaller the exchange rate, the closer the relationship between the two genes, the closer the chain, and conversely, the greater the exchange rate, the farther away the two genes are, the looser the chain. Chain analysis is the determination of gene-to-gene exchange values, and determine the sequence between genes, to map the chain genetic map (linkage map). Chain analysis allows you to determine the relative position of a gene on a chromosome, and is therefore also known as gene location.genetic positioning is an important part of the research on the basis of new characteristics/genes. A common method of gene positioning is the three-point test cross, which determines the relative position and genetic distance of three pairs of genes on chromosomes through a hybridization and a test. Compared with the two-point test, the three-point test is simple to operate, and can eliminate the interference of double switching to a certain extent, and the resulting exchange value can more accurately reflect the genetic distance between the two genes.three pairs of characters known to control the seeds of Zea mays: colored (C)/colorless (c), full (Sh)/depression (sh), and genes that are not Wx/wx are located on chromosome 9. Cross-breeding with seed-colored full non-indentation (CCShShWxWx) and colorless depression self-intercourse (ccshhwxwx), hybrid F1 and triple recessive colorless depression (ccs) hshwxwx) self-intersecting, or F1 self-intersecting, and then based on the number of subseeds and their proportions of each esoterype on the cross-breeding (cross-breeding generation) or self-handed fruit spike, the exchange value between genes is estimated;, experimental materialZea mays fruit spike; (colored full non-shWxWx× colorless depression (ccshhwxwx)) F1× colorless concave The cross-fruit spike of ccshwxwx; the self-confessed fruit spike of F1 (CCShShWxWx) × colorless depression (ccshhwxwx) F1., experimental instruments and appliances,calculators, counters.5, experimental steps(i) to determine the exchange value 1. Measurement method for test corn measurement fruit spike, according to the grain color / colorless, full / depression two pairs of relative characteristics of the four combined esomeels, observation and counting of the sequential seed (measurement subgene generation) of various esomeels, fill in the table below, summarize the whole class (group) data, and calculate its exchange value.b-c
exchange value of x100%
a-b-c-d2. Self-delivery method for the trial of corn self-delivery fruit spike, according to the aforementioned method to observe the count from the four esocial grain (F2) of the exchange, in the upper category, k represents the hundred points of the double hidden individual. Fill in the table below, summarize the class data, and calculate its exchange value.d
double recessive individual percentage k s x100%
a sb sc s d
exchange value s s 1-2 (k opener) s x 100%(ii) Three-point test 1. Observation count take three pairs of relative symptoms of the test corn to measure the fruit spike, count its grain number according to 8 seed espics, fill in the table below, summarize the whole class (group) data. 。 2. Analysis and calculation (1) To determine the genetic relationship of 3 pairs of genes Of the 8 esoteric models listed in the table, 2 esoterics are relatively close in proportion to a total of 4 groups, indicating that these 3 pairs of genes are chained on the same pair of chromosomes. (2) determines that the group with the most observations in the intersection generation is parent, the least group is dual-switched, and the remaining two groups are single-switched. (3) Determine the order of 3 pairs of genes In a double-exchange type, if two pairs of symptoms appear as a parent combination type, then the genes that control the third pair of sexes must be located between the two pairs of genes. For example, in the double-exchange type of this experiment, the combination type of colored non-indentation and colorless non-coloration, respectively, is the parent, then the pair of genes that control fullness/depression must be located between the two pairs of genes mentioned above. (4) to calculate the exchange value and fill in the table. double switching value of s (g-h)/T×l00%. 。 3. Mapping chain genetic map based on the above estimated single-exchange values I, II and double-switching values, determine the order of 3 pairs of genes, draw a chain genetic map. , the experimental 1. Is the exchange value of the measurement method and the self-exchange method equal? Why? 。 2. Map and analyze the chain genetics of the three pairs of genes C/c, Sh/sh and Wx/wx. 。