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Drosophila Lab_ Exploring Genetics


									Drosophila Lab: Exploring Genetics
AP recommended lab

Two Tasks to Complete
1. Pre-lab Questions from 12 Recomm. Labs (link from my website)

2. Computer Simulated Lab: “Gene Pool” drive ***Answer Questions on a separate paper.

To Access the Lab Simulation for Drosophila
• Click the “START” and choose “My Computer” • Type in the following:

• Choose the “Drosophila folder” and double click the “Neo” application. • Follow the instructions and answer the guiding questions listed on the front page of your lab.

Key Parts for Drosophila Lab
• • • • Stages of Drosophila Main Characteristics to observe (4) Determining Male vs. Female (3) Examine 3 Modes of Inheritance:
Monohybrid: Dihybrid: Sex-Linked: Red Eyes x Sepia Eyes Eye color, Wing White eyed-female x Red eyed Male (X? X ? ) • (X ? y )

Observed Values
• Table 7.2: F2 Generation -78 red-eyed females -62 white-eyed females -69 red-eyed males -73 white eyed males Expected Results: Complete #3 (both Tables) Do a Chi-square analysis. **Note: Critical values are listed in Table 7.5 on the bottom of Page 86.

Crosses to Complete for Lab #6
1) Table 7.1: F1 Generation Data
Phenotype and Symbol

all XRXr

Males all XrY

Red-eyed White-eyed

Phenotype and Symbol

F2 Generation: Sex-Linked trait
Females 78 XRXr Males 69 XRY

Red-Eyed (XR)

White-Eyed (Xr)

62 XrXr

73 XrY

Assume that the following Data was obtained and determine if it is significant or not by calculating a Chi-Square value.

Answer for First Cross
X2 = (78-72) 2 + (69-71)2 + (62-71)2 + (73-71)2 71 71 71 71 X2 = 0.69 + 0.06 + 1.14 + 0.06 X2 = 1.94 Degrees of freedom: (4 categories) 3 Critical Value: see Table7.3 (pg.85) 7.82 The chi-squared value is less than 7.82 Therefore:Our null hypothesis is accepted: That there is not a significant difference between the observed value and expected value. We must then accept that our results follows the expected (theoretical value).

nd 2

Genetic Cross

• • • • • •

Red-Eyed: Dominant Sepia eyes: Recessive Parental cross: F1 Cross: F1: F2:

SS X ss Ss X Ss All Ss 3:1 (red:sepia)

Observed Values for #7 (table)
Phenotype Red-Eyed sepia Total: # Observed 140 60 200 offspring # Expected calc. value calc. Value

Complete Questions #6 & 7

Data for Second Cross
Phenotype # observed (o) # Expected (e)








Other Crosses to do
• Pg 86: Green & Albino seedlings • Pg.88: Long & short winged flies **complete and calculate Chi-Square values to determine if the results are significant and acceptable (statistically valid)

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