Mendel's laws include the "law of segregation" and the "law of independent distribution". According to the law of segregation, a pair of alleles located on a pair of homologous chromosomes will segregate from each other during meiosis to form gametes, and will be assigned to different gametes without interfering with each other. Therefore, for a heterozygote with one pair of genes, under the condition of complete dominance, the segregation ratios of expression in its selfed and tested offspring are 3:1 and 1:1, respectively.The Law of Independent Assignment (Law of Free Combination) further reveals the relationship between segregation and combination of multiple pairs of independently inherited genes located on non-homologous chromosomes. According to this law, two pairs of genes located on non-homologous chromosomes are segregated separately according to the law of segregation during meiosis, and free combinations can occur between the two pairs of genes, resulting in the production of four types of gametes in equal proportions. Therefore, for a heterozygote with two pairs of genes, under the condition of complete dominance, the ratio of segregation of phenotypes in its selfed and tested offspring is 9:3:3:1 and 1:1:1:1, respectively.
Operation method
Segregation-independent assignment of genes and intercropping experiments
Principle
Mendel's laws include the "law of segregation" and the "law of independent distribution". According to the law of segregation, a pair of alleles located on a pair of homologous chromosomes will segregate from each other during meiosis to form gametes, and will be assigned to different gametes without interfering with each other. Therefore, for a heterozygote with one pair of genes, under the condition of complete dominance, the segregation ratios of expression in its selfed and tested offspring are 3:1 and 1:1, respectively.The Law of Independent Assignment (Law of Free Combination) further reveals the relationship between the segregation and combination of multiple pairs of independently inherited genes located on non-homologous chromosomes. According to this law, two pairs of genes located on non-homologous chromosomes are segregated separately according to the law of segregation during meiosis, and free combinations can occur between the two pairs of genes, resulting in the production of four types of gametes in equal proportions. Therefore, for a heterozygote with two pairs of genes, under the condition of complete dominance, the expression segregation ratios of its selfed offspring and tested offspring are 9:3:3:1 and 1:1:1:1, respectively.The study of gene interactions is about the genes which are located on non-homologous chromosomes and are genetically independent and jointly controlled by a pair of relative traits, and there are some ways to interactions such as complementation, overlapping, cumulative addition, uplifting, and inhibition, etc. The above mentioned ways, although the expressions of the genes are not the same as the genes, are not the same as the genes. The above ways of intercropping despite the different proportion of segregation of expression types, but the gene segregation and combination still follow the law of independent distribution. Maize used to be an important material for genetic research, and the inheritance of grain traits is a basic element of maize genetic research. Genetic analysis of kernels through crosses of maize with various relative traits of kernels helps us to have a deeper understanding of the laws of segregation, independent inheritance and different ways of gene interactions. The maize seed kernel consists of three parts: pericarp, endosperm and embryo (shown in Figure 1). They have different generations and genetic bases. The pericarp, which is formed by the healing of the pericarp formed by the ovary wall and the seed coat formed by the bead covers, is part of the maternal tissue and is diploid (2n) with the same genotype as the parent. The endosperm and embryo are products of double fertilization, the embryo is diploid (2n) and the endosperm is triploid (3n) and is divided into a dextrinous and a starchy layer. The pericarp, the dextrins and the starch layer all exhibit a certain color, which ultimately affects the color of the kernel. The formation of maize starch layer pigmentation involves the following pairs of genes: the anthocyanin genes Alal, A2a2, A3a3; the starch color genes Cc, Rr, PrPr, and the pigmentation repressor gene Ii. The mechanism by which these pairs of genes control the color of the grain is as follows: pigment can only be formed when the dominant genes Al, A2, A3, C, R are present at the same time and the suppressor genes are recessive and pure ii; and the category of pigment formation is determined by Prpr, which is purple when the dominant gene Pr is present, and red when the recessive gene is pure prpr is present. When any or all of these pigmentation genes are missing in the dominant genes A1, A2, A3, C, and R are dominant, but when the dominant repressor gene I is present, they all appear colorless. The color of the starch layer is distinguished between yellow and white, and yellow is dominant to white, controlled by a pair of alleles. The above traits related to the pasty and starchy layers of the endosperm often exhibit pollen directness. Pollen directness is a manifestation of a dominant trait in the seed, when the parent pollen contains a dominant gene, the trait it controls may be manifested in the seed of a contemporary hybrid, while the pericarp does not manifest directness because it is not related to fertilization.
Materials and Instruments
Corn on the cob Move I. Experimental content and steps Table 1 Table of results of analysis of a pair of inherited traits Table 2 Table of results of analysis of two pairs of independent genetic traits 3. Fill in Table 3 with the results of the analysis of gene interactions and give a rational explanation. For more product details, please visit Aladdin Scientific website.
calculator
Take corn cobs of different hybrid combinations, observe and count the number of kernels of different phenotypes, and fill in the statistical results in the table in the calculation of the results of the fourth experiment.
1. Analysis of a pair of genetic traits: purple × white hybrid progeny F1 self-crossed cob and measured cob.
2. Analysis of two pairs of independent genetic traits: F1 self-crossed ears of a maize cross with purple full × white wrinkled kernels.
3. Analysis of the genetic trait of gene complementation: self-crossed ears of F1 maize cross with purple × white kernels.
Calculation of experimental results
1. Fill in Table 1 with the results of the analysis of a pair of genetic traits and state whether the actual observations are consistent with the theoretical inferences.
2. Fill in Table 2 with the results of the analysis of the two independent pairs of inherited traits and state whether the actual observations are consistent with the theoretical inferences.
Table 3 Table of results of analysis of gene interactions for traits