Design and Practice of a New Teaching Project of the Map-based Cloning Experiment in Genetics

doi:10.11983/CBB19107

Abstract

Abstract: Recombination, linkage and crossover of chromosomes are the key and difficult points in genetics teaching. For students’ comprehensively understanding these concepts in teaching, we designed a new genetic experiment named ‘Gene mapping using DNA molecular markers’ based on the principle of the map-based cloning method, using our previous studies on cloning of a rice lesion-mimic phenotype regulating gene SPOTTED LEAF 5 (SPL5) as an example. In this experiment, students are instructed to perform the linkage analysis, genetically map the spl5 mutation and align a genetic map by using an F₂ population generated by a cross between spl5 and wild-type plants and polymorphic molecu- lar markers. This teaching experiment can not only effectively promote students' understanding of the three Laws of genetics, but also be helpful to broaden their vision and improve their ability to solve problems and work in a team.

Key words: genetics, comprehensive designing experiment, map-based cloning, educational resources

Xifeng Chen,Yaping Liu,Bojun Ma. Design and Practice of a New Teaching Project of the Map-based Cloning Experiment in Genetics[J]. Chinese Bulletin of Botany, 2019, 54(6): 797-803.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB19107

https://www.chinbullbotany.com/EN/Y2019/V54/I6/797

Figures/Tables 5

Figure 1 Recombination patterns between the target gene and the molecular markers during meiosis A and a represent a pair of dominant and recessive alleles, of which AA and Aa show dominant phenotypes and aa shows a recessive phenotype; M and m represent a given molecular marker at the same locus derived from the dominant parent (AA) and the recessive parent (aa), respectively.

Figure 2 The phenotype of the rice spl5 lesion mimic mutant and a schematic workflow of generation of the genetic mapping population (A) The plant phenotype of wild-type control Nipponbare, a Japonica rice cultivar, and the spl5 mutant; (B) The leaf phenotype of wild-type control and the spl5 mutant; (C) A workflow showing the generation of an F2 mapping population by crossing an Indica cultivar 9311 with the spl5 mutant.

Table 1 PCR primers of the SSR markers used in this study

SSR标记	正向引物 (5°-3°)	反向引物 (5°-3°)
RM21103	ACAAGTCCACAAGGACCACAACC	TGCTCCACCCAAAGATACAGAGC
RM21309	GAGTGGATTTACTGACAAGCTCTTCC	GATTCTCTTGGAGCCCATACTCC
RM21470	TCTTGCCATCACATAGCAACAGG	ACTCGGTGAGCATCCAATGTCC
RM22426	ATTTCGTCGTCGTGTCTGTCC	TTAAAGCAGCCTGATCGAAAGC
RM22648	AGCAGCTCCGATTGTGTTAGCC	AATGGCGTCTGTGGTACTTTGC
RM22925	CGATTACCAGGACAACAGATCACG	GTGGCTCTTGAGTGTACGTGTGC

Figure 3 Linkage analysis and genetic mapping of the SPL5 gene (A) A physical map of the SSR markers on chromosomes used in this study; (B) Analysis of the PCR products of the SSR markers by electrophoresis; (C) A genetic linkage map of the SPL5 gene.

Table 2 The Chi-square (χ2) test for the genotype separation ratio of the SSR markers in this study

分子标记	20个F₂突变型单株中各基因型的数量			χ²值	P值
分子标记	MM	Mm	mm	χ²值	P值
RM21103	0	0	20	60	<0.01
RM21309	0	3	17	38.7	<0.01
RM21470	1	7	12	13.9	<0.01
RM22426	4	11	5	0.3	>0.05
RM22648	5	9	6	0.3	>0.05
RM22925	7	10	3	1.6	>0.05

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