sex linked inheritance in Drosophila melanogaster white eye color

2.  Drosophila was one of the first organisms to be studied
genetically due to its:
 small size, less space is needed to maintain the
population.
 short life cycle,
 high reproductive rate,
 Many different species, and a large number and wide
variety of naturally-occurring and artificially-induced
genetic variants are available.

3. For Drosophila, standard culture medium must be made
which should be nutritious, inexpensive, have a high
moisture content and a firm texture, and be resistant to
mould and bacterial contamination.
 Semolina: 100g : contains carbohydrate 85%,
protein 15%
 Jaggery: carbohydrate 100g.
 Propionic acid: fly food preservative 7.5ml.
 Agar agar: solidification of medium 10g.
 Yeast : protein supply
 Water: solvent

5.  Polyandrous
 stores sperms in the spermatheca.
Avoids contamination of crosses bottle.
After collecting the virgin flies, we have to keep them
for aging.
Aging is done to know whether the collected virgins are
contaminated or not.

7. Crosses are then set up.
Direct cross: 10 virgin red-eyed female is crossed with 10
white-eyed males.
Reciprocal cross: 10 virgin white-eyed females are
crossed with 10 red-eyed males.
We allowed the cross to develop for 7 days.
F1 progenies were isolated and phenotypes were
examined.

8. Direct cross
Reciprocal cross
Reciprocal cross

11. DATE RED EYED FEMALES RED EYED MALES
2/11 76 95
5/11 19 28
9/11 15 30
12/11 38 33
18/11 62 66
22/11 77 56
26/11 47 25
30/11 7 4
TOTAL 341 337
Total number of F1 flies-678

12. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
341 339 2 4 0.01
RED EYE
MALE
337 339 2 4 0.01
χ²=0.02

13. DATE RED EYED FEMALES RED EYED MALES
2/11 19 22
5/11 40 45
8/11 6 16
9/11 4 9
12/11 41 44
14/11 27 18
TOTAL 126 154
Total number of F1 flies-280

14. PHENOTY
PE
OBSERVE
D
VALUE(O)
EXPECTE
D
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
126 140 14 196 1.4
RED EYE
MALE
154 140 6 36 0.26
χ²=1.66

15. DATE RED EYED FEMALES RED EYED MALES
3/11 25 27
6/11 34 26
10/11 46 31
15/11 75 85
18/11 81 66
21/11 25 36
23/11 22 32
25/11 19 29
TOTAL 327 332
Total number of F1 flies-659

16. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
327 329.5 6.25 39.06 0.12
RED EYE
MALE
332 329.5 2.5 6.25 0.02
χ²=0.14

17. Phenotype Observed Expected
proportio
n
Expected
no.
χ² Accepted
or rejected
Red eye
female
141 1/2 139 0.02 Accepted
Red eye male 137 1/2 139 0.02 Accepted

18. DATE RED EYED
FEMALES
WHITE EYED MALES
21/10 37 24
25/10 46 67
28/10 61 39
03/11 79 75
07/11 63 47
12/11 13 15
TOTAL 298 274
Total number of F1 flies- 572

19. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
298 286 12 144 0.50
WHITE EYE
MALE
274 286 12 144 0.50
χ²=1

20. DATE RED EYED
FEMALES
WHITE EYED MALES
02/11 47 63
05/11 85 74
09/11 66 67
12/11 63 58
14/11 51 35
18/11 6 7
TOTAL 318 306
Total number of F1 flies- 624

21. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
318 312 6 36 0.12
WHITE EYE
MALE
306 312 6 36 0.12
χ²=0.24

22. DATE WHITE EYED
MALES
RED EYED FEMALES
16/11 13 47
18/11 105 69
21/11 60 57
23/11 20 22
25/11 16 13
28/11 4 3
TOTAL 218 211
Total number of F1 flies- 429
DATE WHITE EYED
MALES
RED EYED FEMALES
16/11 13 47
18/11 105 69
21/11 60 57
23/11 20 22
25/11 16 13
28/11 4 3
TOTAL 218 211

23. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
218 214.5 3.5 12.25 0.06
WHITE EYE
MALE
211 214.5 3.5 12.25 0.06
χ²=0.12

24. cross χ² Accepted or
rejected
Direct1 0.02 Accepted
Direct2 1.66 Accepted
Direct3 0.14 Accepted
Reciprocal1 1 Accepted
Reciprocal2 0.24 Accepted
Reciprocal3 0.12 Accepted

25. Asymmetric:
In direct cross, we could only find red eyed F1
progenies. Therefore we can conclude that red is the
dominant.

26. In reciprocal cross only F1 males were having white-
eye phenotype. This shows sex bias, hence it is present
on sex chromosome.
As only males are affected and females are not affected,
we could predict that it may be sex limited inheritance
or sex linked.
This may be because females consist of two X
chromosome and male only I X chromosome.
May be red-eye allele is dominant over white-eyed.

28.  F1 selfing was carried out
 Ten F1 females were crossed with ten F1
males
 We got F2 progeny in the ratio of
2 red female: 1 red male: 1 white male

29. DATE RED EYE FEMALE RED EYE MALE WHITE EYE MALE
16/11 43 9 10
18/11 52 28 25
19/11 39 28 14
21/11 181 65 54
22/11 37 34 15
23/11 47 29 21
25/11 53 26 23
26/11 26 11 7
29/11 67 27 33
TOTAL 545 257 202
Total no. of F2 progeny-1004

30. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
545 502 43 1849 3.68
RED EYE
MALE
257 251 6 36 0.14
WHITE EYE
MALE
202 251 49 2401 9.56
χ²=13.38

31. DATE RED EYE FEMALE RED EYE MALE WHITE EYE MALE
18/11 89 28 31
19/11 29 12 19
21/11 60 26 19
22/11 35 7 9
23/11 21 19 8
26/11 42 24 19
29/11 56 28 36
30/11 38 21 12
3/12 64 32 32
TOTAL 426 197 185
Total no. of F2 progeny-808

32. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
426 404 22 484 1.19
RED EYE
MALE
197 202 5 25 0.12
WHITE EYE
MALE
185 202 17 289 1.43
χ²=2.63

33. DATE RED EYE FEMALE RED EYE MALE WHITE EYE MALE
19/11 12 - -
21/11 43 18 5
22/11 16 12 11
25/11 53 24 12
26/11 4 2 3
28/11 23 4 10
29/11 8 2 1
30/11 3 1 3
TOTAL 162 58 45
Total no. of F2 progeny-265

34. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
162 132.5 29.5 870.2 6.56
RED EYE
MALE
58 66.25 8.25 68.06 1.03
WHITE EYE
MALE
45 66.25 21.25 451.56 6.81
χ²=14.4

36. DATE RED EYE
FEMALE
WHITE EYE
FEMALE
RED EYE
MALE
WHITE EYE
MALE
2/11 4 2 - -
5/11 28 29 37 28
9/11 44 55 52 57
14/11 44 60 34 32
18/11 23 25 24 19
22/11 24 15 7 13
25/11 12 9 4 4
28/11 6 4 7 9
29/11 4 4 6 3
TOTAL 185 200 171 171
TOTAL NUMBER OF F2 PROGENY-
727

37. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
185 181.75 3.25 10.56 0.058
WHITE EYE
FEMALE
200 181.75 18.25 333.06 1.833
RED EYE
MALE
171 181.75 10.75 115.56 0.636
WHITE EYE
MALE
171 181.75 10.75 115.56 0.636
χ² = 3.163

38. DATE RED EYE
FEMALE
WHITE EYE
FEMALE
RED EYE
MALE
WHITE EYE
MALE
16/11 11 5 6 7
19/11 65 57 69 72
22/11 41 40 54 56
25/11 40 39 45 32
28/11 19 21 22 30
30/11 28 31 25 24
5/12 16 15 8 20
6/12 24 7 5 13
TOTAL 236 208 230 246
TOTAL NUMBBER OF F1 PROGENY - 920

39. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
236 230 6 36 0.157
WHITE EYE
FEMALE
208 230 22 484 2.104
RED EYE
MALE
230 230 0 0 0
WHITE EYE
MALE
246 230 16 256 1.113
χ² = 3.374

40. DATE RED EYE
FEMALE
WHITE EYE
FEMALE
RED EYE
MALE
WHITE EYE
MALE
24/11 1 2 2 1
26/11 2 12 11 11
28/11 59 50 56 63
29/11 11 9 10 10
30/11 20 15 28 16
3/12 40 28 44 54
4/12 8 20 11 17
5/12 33 49 25 56
6/12 9 14 8 12
TOTAL 183 199 195 240
TOTAL NUMBER OF F2

41. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
183 204.25 21.25 451.56 2.21
WHITE EYE
FEMALE
199 204.25 5.25 27.56 0.135
RED EYE
MALE
195 204.25 9.25 85.56 0.42
WHITE EYE
MALE
240 204.25 35.75 1278.06 6.26
χ² = 9.025

42. CROSS χ² ACCEPTED OR REJECTED
DIRECT F1 1 13.38 REJECTED
DIRECT F1 2 2.63 ACCEPTED
DIRECT F1 3 14.4 REJECTED
RECIPROCAL F1 1 3.163 ACCEPTED
RECIPROCAL F1 2 3.37 ACCEPTED
RECIPROCAL F1 3 9.025 REJECTED

43.  ASYMMETRIC
 NOT SHOWING SEX LIMITED INHERITANCE
 SKIPPING OF GENERATION
 CRISS CROSS
 MORE NUMBER OF MALE IS EFFECTED

44. How to identify whether F1 progeny
are in homozygous or heterozygous
condition?

45. To confirm whether the given parental flies are in
homozygous or heterozygous condition we need to
conduct test cross
Test cross was conducted by using virgin F1 female with
recessive male parent.

47. DATE RED EYE
FEMALE
WHITE EYE
FEMALE
RED EYE MALE WHITE EYE
MALE
27/11 31 14 29 20
28/11 14 20 25 17
29/11 28 33 31 45
30/11 37 35 27 34
2/12 47 59 32 36
3/12 28 25 23 30
5/12 7 11 7 5
TOTAL 192 197 174 189
TOTAL NUMBER OF PROGENIES - 752

48. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
192 188 4 16 0.085
WHITE EYE
FEMALE
197 188 9 81 0.43
RED EYE
MALE
174 188 14 196 1.04
WHITE EYE
MALE
189 188 1 1 0.005
χ²=1.56

49. DATE RED EYE
FEMALE
WHITE EYE
FEMALE
RED EYE MALE WHITE EYE
MALE
27/11 14 8 5 11
28/11 18 12 31 18
29/11 34 24 26 35
30/11 42 32 32 38
2/12 76 74 70 97
3/12 16 10 18 10
5/12 41 48 25 33
TOTAL 241 210 207 242
TOTAL NUMBER OF PROGENIES - 900

50. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
RED EYE
FEMALE
241 225 16 256 1.14
WHITE EYE
FEMALE
210 225 15 225 1
RED EYE
MALE
207 225 18 324 1.44
WHITE EYE
MALE
242 225 17 289 1.28
χ²= 4.86

52. DATE WHITE EYED FEMALES WHITE EYED MALES
8/11 23 25
9/11 37 16
12/11 133 126
15/11 66 40
18/11 22 23
21/11 19 20
25/11 2 5
29/11 6 12
TOTAL 342 360
TOTAL NUMBER OF PROGENIES- 702

53. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
WHITE EYE
MALE
342 351 9 81 0.23
WHITE EYE
FEMALE
360 351 9 81 0.23
χ²= 0.46

54. DATE WHITE EYED MALES WHITE EYED FEMALES
18/11 18 5
19/11 45 24
21/11 96 73
23/11 38 45
25/11 36 54
28/11 43 68
30/11 18 26
5/12 53 57
TOTAL 347 352
TOTAL NUMBER OF PROGENIES- 699

55. PHENOTYP
E
OBSERVED
VALUE(O)
EXPECTED
VALUE(E)
(O-E) (O-E)² (O-E)²/E
WHITE EYE
MALE
347 349.5 2.5 6.25 0.018
WHITE EYE
FEMALE
352 349.5 2.5 6.25 0.018
χ²=0.036

56. CROSS χ² ACCEPTED OR
REJECTED
DIRECT TEST CROSS11 1.56 ACCEPTED
D. TEST CROSS 1 2 4.86 ACCEPTED
D. TEST CROSS 1 3 6.46 ACCEPTED
RECIPROCAL TEST
CROSS 1. 1
0.46 ACCEPTED
R. TESTCROSS 1 2 0.03 ACCEPTED

57.  Used to determine the phenotype of the F1
generation
 Supports the idea that reappearance of the
recessive character in the F2 is due to the
heterozygous condition of the F1 plant

58.  Does not obey law of equivalence of direct and
reciprocal cross and hence it is a non mendelian
inheritance
 In direct cross, F2 Ratio is appx. 3:1 which is
comparable to Mendel’s monohybrid ratio but in
reciprocal cross, F2 ratio is appx. 1:1.
 So, we confirm that the genes controlling the eye
color present on X chromosome.
 Reciprocal cross shows criss cross inheritance

59. Criss-cross mode of inheritance is a significant
character.
Number of male having mutated allele in comparison
with female.
Therefore, we can conclude that the given allele is
showing X-linked recessive inheritance.

60.  We can study the inheritance pattern of the
Drosophila and compare this with that of
inheritance of human.