课程介绍 Course Introduction
学分：3 | 先修课：普通生物学 | 学期：第三学期
本课程系统阐述遗传学的基本原理和方法，内容包括孟德尔遗传定律、染色体遗传、连锁与交换、基因定位、基因突变、染色体畸变、细胞质遗传、数量遗传、群体遗传以及分子遗传学基础。课程结合人类遗传病案例进行讲解，培养学生运用遗传学原理分析和解决生物医学问题的能力。
This course systematically presents fundamental principles and methods of genetics. Topics include Mendelian inheritance, chromosomal genetics, linkage and crossing over, gene mapping, gene mutation, chromosomal aberrations, cytoplasmic inheritance, quantitative genetics, population genetics, and molecular genetics basics. The course uses human genetic disease cases for instruction.
Steps
Step 1
Drosophila Strain Selection and Cross Experiment Design
The core task of this step is to select appropriate Drosophila mutant strains and design a scientific crossing experiment protocol. It requires comprehensive consideration of dominant/recessive traits, sex-linkage, and feasibility of gene mapping.
• Choose 2-3 pairs of contrasting traits from red/white eyes (X-linked), long/vestigial wings (autosomal), gray/black body (autosomal), straight/javelin bristles, etc.; determine gene symbols and dominance relationships
• Design crossing scheme: include reciprocal crosses (wild type ♀ × mutant ♂ and mutant ♀ × wild type ♂), F1 selfing or intercrossing, F1 test cross with recessive homozygote; determine cross combinations and numbers for each generation
• Prepare Drosophila culture medium (cornmeal-sucrose-yeast formula: cornmeal 10g, sucrose 10g, yeast 2g, agar 1g, water 100ml, propionic acid 0.5ml); prepare culture vials, anesthesia bottles, ether, dissecting microscope, brush; set culture temperature 25°C, relative humidity 60%
Deliverable: Cross experiment design proposal (strain selection, cross combination diagram, medium formula, equipment list, culture conditions, expected results) | Quality standard: Scientific and reasonable design, appropriate cross combinations, adequate material preparation, clear expected results
Step 2
Parental Culture and Virgin Female Collection
The core task of this step is to propagate parental Drosophila strains and collect virgin females to ensure accuracy of crosses. The key to Drosophila crossing experiments is guaranteeing females have not mated before crossing, so virgin female collection is critical for experimental success.
• Parental propagation: inoculate wild type and each mutant strain into fresh culture medium, 5-8 pairs per vial, culture at 25°C for 7-10 days; remove parental adults after pupation
• Virgin female collection: collect twice daily at 8am and 8pm; lightly anesthetize with ether; distinguish males and females under dissecting microscope (males have rounded abdomen tip with black genitalia, females have pointed abdomen with stripes); culture females alone for 2-3 days to verify no egg-laying
• Parental crossing: cross virgin females with corresponding males according to experimental plan; place 5-10 pairs per culture vial; label with cross combination, date, name; culture at 25°C; remove parental adults after 7 days
Deliverable: Lab notebook (parental propagation records, virgin female collection numbers and verification, cross combination setup records), culture vials for each cross | Quality standard: Accurate virgin female collection (verified no eggs), correct cross combinations, healthy parents
Step 3
Offspring Culture and Phenotype Observation & Scoring
The core task of this step is to culture F1 and F2 generation flies, observe and count individuals of each phenotype. Phenotype observation requires accurate identification of mutant traits, and scoring needs sufficiently large sample size to ensure statistical power.
• F1 observation: 7-10 days after parental cross, when F1 adults emerge; anesthetize and observe F1 phenotypes; record numbers and phenotypes of males and females; determine dominance relationships and sex-linkage; select F1 for intercross or test cross
• F2 culture: place 5-10 pairs of F1 males and females into fresh culture vials; culture at 25°C; remove F1 adults after 7 days; wait for F2 emergence
• F2 phenotype scoring: collect F2 adults daily; anesthetize and observe/identify phenotypes (eye color, wing shape, body color, bristle morphology, etc.) under dissecting microscope; distinguish males and females; count by category; score at least 200 flies per cross combination; continue scoring for 5-7 days until emergence is complete
Deliverable: Phenotype data statistics table (numbers of each phenotype by sex, totals, ratios for each generation), experimental observation records | Quality standard: Accurate phenotype identification, sufficient sample size (>200 flies), complete data records
Step 4
Chi-Square Test and Gene Mapping Analysis
The core task of this step is to statistically analyze experimental data, perform chi-square tests to verify genetic laws, calculate recombination frequency between genes, and perform gene mapping. Chi-square test determines whether observed values match theoretical expectations.
• Chi-square (χ²) test: calculate theoretical expected values based on Mendelian laws (e.g., 3:1 ratio for monohybrid F2, 9:3:3:1 for dihybrid F2); calculate chi-square value χ² = Σ[(observed-expected)²/expected]; determine degrees of freedom; check chi-square table for P value
• Recombination frequency calculation: for dihybrid or trihybrid crosses, calculate proportion of recombinant individuals among total (recombination frequency = recombinants/total × 100%); unit is centimorgan (cM), 1cM = 1% recombination
• Gene mapping: use three-factor cross to determine gene order and genetic distances; calculate double crossover rate and coefficient of coincidence; draw genetic linkage map with map distances between genes
Deliverable: Genetic analysis report (chi-square test calculation process, recombination frequency calculation, genetic linkage map, coefficient of coincidence) | Quality standard: Correct statistical methods, accurate gene mapping, standard genetic map drawing
Step 5
Genetic Analysis Report Writing and Discussion
The core task of this step is to write a complete genetic analysis lab report systematically presenting experimental design, procedures, data results, and genetic analysis. The report should include detailed experimental data, statistical analysis process, and gene mapping results.
• Write according to genetics lab report standards: abstract, introduction, materials and methods, experimental results, analysis and discussion, conclusion, references; minimum 3000 words
• Create complete data figures: cross combination diagrams, segregation ratio data tables, chi-square test tables, recombination frequency calculation tables, genetic linkage maps
• In-depth discussion: analyze whether results conform to Mendelian laws, discuss factors affecting recombination frequency, compare accuracy of gene mapping, analyze sources of experimental error (sample size, environmental factors, counting bias, etc.), propose improvement suggestions
Deliverable: Complete genetic analysis lab report (PDF format with experimental data, statistical analysis, genetic maps), raw data records | Quality standard: Complete structure, detailed data, in-depth analysis, accurate genetic concepts, meaningful discussion
Steps
Step 1
Drosophila Strain Selection and Cross Experiment Design
The core task of this step is to select appropriate Drosophila mutant strains and design a scientific crossing experiment protocol. It requires comprehensive consideration of dominant/recessive traits, sex-linkage, and feasibility of gene mapping. Cross combinations include reciprocal crosses, test crosses, etc. Scientific experimental design is the foundation for reliable genetic data, directly affecting the accuracy of subsequent gene mapping analysis.
• Choose 2-3 pairs of contrasting traits from red/white eyes (X-linked), long/vestigial wings (autosomal), gray/black body (autosomal), straight/javelin bristles, etc.; determine gene symbols and dominance relationships
• Design crossing scheme: include reciprocal crosses (wild type ♀ × mutant ♂ and mutant ♀ × wild type ♂), F1 selfing or intercrossing, F1 test cross with recessive homozygote; determine cross combinations and numbers for each generation
• Prepare Drosophila culture medium (cornmeal-sucrose-yeast formula: cornmeal 10g, sucrose 10g, yeast 2g, agar 1g, water 100ml, propionic acid 0.5ml); prepare culture vials, anesthesia bottles, ether, dissecting microscope, brush; set culture temperature 25°C, relative humidity 60%
Deliverable: Cross experiment design proposal (strain selection, cross combination diagram, medium formula, equipment list, culture conditions, expected results) | Quality standard: Scientific and reasonable design, appropriate cross combinations, adequate material preparation, clear expected results
Step 2
Parental Culture and Virgin Female Collection
The core task of this step is to propagate parental Drosophila strains and collect virgin females to ensure accuracy of crosses. The key to Drosophila crossing experiments is guaranteeing females have not mated before crossing, so virgin female collection is critical for experimental success. It requires understanding Drosophila development cycle and collecting virgins within 8 hours of eclosion before reproductive system maturation.
• Parental propagation: inoculate wild type and each mutant strain into fresh culture medium, 5-8 pairs per vial, culture at 25°C for 7-10 days; remove parental adults after pupation
• Virgin female collection: collect twice daily at 8am and 8pm; lightly anesthetize with ether; distinguish males and females under dissecting microscope (males have rounded abdomen tip with black genitalia, females have pointed abdomen with stripes); culture females alone for 2-3 days to verify no egg-laying
• Parental crossing: cross virgin females with corresponding males according to experimental plan; place 5-10 pairs per culture vial; label with cross combination, date, name; culture at 25°C; remove parental adults after 7 days
Deliverable: Lab notebook (parental propagation records, virgin female collection numbers and verification, cross combination setup records), culture vials for each cross | Quality standard: Accurate virgin female collection (verified no eggs), correct cross combinations, healthy parents
Step 3
Offspring Culture and Phenotype Observation & Scoring
The core task of this step is to culture F1 and F2 generation flies, observe and count individuals of each phenotype. Phenotype observation requires accurate identification of mutant traits, and scoring needs sufficiently large sample size to ensure statistical power. Phenotype identification requires careful observation under dissecting microscope, distinguishing sex and different traits.
• F1 observation: 7-10 days after parental cross, when F1 adults emerge; anesthetize and observe F1 phenotypes; record numbers and phenotypes of males and females; determine dominance relationships and sex-linkage; select F1 for intercross or test cross
• F2 culture: place 5-10 pairs of F1 males and females into fresh culture vials; culture at 25°C; remove F1 adults after 7 days; wait for F2 emergence
• F2 phenotype scoring: collect F2 adults daily; anesthetize and observe/identify phenotypes (eye color, wing shape, body color, bristle morphology, etc.) under dissecting microscope; distinguish males and females; count by category; score at least 200 flies per cross combination; continue scoring for 5-7 days until emergence is complete
Deliverable: Phenotype data statistics table (numbers of each phenotype by sex, totals, ratios for each generation), experimental observation records | Quality standard: Accurate phenotype identification, sufficient sample size (>200 flies), complete data records
Step 4
Chi-Square Test and Gene Mapping Analysis
The core task of this step is to statistically analyze experimental data, perform chi-square tests to verify genetic laws, calculate recombination frequency between genes, and perform gene mapping. Chi-square test determines whether observed values match theoretical expectations. Recombination frequency calculation determines relative positions and genetic distances of genes on chromosomes.
• Chi-square (χ²) test: calculate theoretical expected values based on Mendelian laws (e.g., 3:1 ratio for monohybrid F2, 9:3:3:1 for dihybrid F2); calculate chi-square value χ² = Σ[(observed-expected)²/expected]; determine degrees of freedom; check chi-square table for P value
• Recombination frequency calculation: for dihybrid or trihybrid crosses, calculate proportion of recombinant individuals among total (recombination frequency = recombinants/total × 100%); unit is centimorgan (cM), 1cM = 1% recombination
• Gene mapping: use three-factor cross to determine gene order and genetic distances; calculate double crossover rate and coefficient of coincidence; draw genetic linkage map with map distances between genes
Deliverable: Genetic analysis report (chi-square test calculation process, recombination frequency calculation, genetic linkage map, coefficient of coincidence) | Quality standard: Correct statistical methods, accurate gene mapping, standard genetic map drawing
Step 5
Genetic Analysis Report Writing and Discussion
The core task of this step is to write a complete genetic analysis lab report systematically presenting experimental design, procedures, data results, and genetic analysis. The report should include detailed experimental data, statistical analysis process, and gene mapping results, with in-depth discussion of agreement between results and theoretical expectations, possible experimental errors, and improvement directions.
• Write according to genetics lab report standards: abstract, introduction, materials and methods, experimental results, analysis and discussion, conclusion, references; minimum 3000 words
• Create complete data figures: cross combination diagrams, segregation ratio data tables, chi-square test tables, recombination frequency calculation tables, genetic linkage maps
• In-depth discussion: analyze whether results conform to Mendelian laws, discuss factors affecting recombination frequency, compare accuracy of gene mapping, analyze sources of experimental error (sample size, environmental factors, counting bias, etc.), propose improvement suggestions
Deliverable: Complete genetic analysis lab report (PDF format with experimental data, statistical analysis, genetic maps), raw data records | Quality standard: Complete structure, detailed data, in-depth analysis, accurate genetic concepts, meaningful discussion