1. SEX- LINKED INHERITANCE

3. Lateral view of a male Fruit Fly (Drosophila melanogaster) showing its red wild type eye. LM

5. P: FEMALE DROSOPHILA X MALE DROSOPHILA
RED- EYED ♀ WHITE-EYED ♂
F1: ALL RED-EYED OFFSPRING
CONCLUSION: RED-EYE GENE IS DOMINANT
P (FROM F1) RED- EYED ♀ X RED-EYED ♂
F2: 3/4 RED-EYED ; /4 WHITE-EYED
♀ AND ♂ ♂ !

9. CONCLUSION: ALL RED-EYED OFFSPRING P (FROM F1): XR Xr X XR Y
P: XR XR X Xr Y
G: 1/1 X 1/ , 1/2
F1: 1/2 X R X r ; 1/2XR Y
CONCLUSION: ALL RED-EYED OFFSPRING
P (FROM F1): XR Xr X XR Y
G: 1/2 XR , 1/2 Xr x 1/2 XR , 1/2 Y
F2: 1/4XR XR ; 1/4 XRXr ; 1/4 XR Y ; 1/4 Xr Y * XR Xr Y
¾ RED-EYED ♀ AND ♂
¼ WHITE-EYED ♂

10. F1: 1/4XR Xr ; 1/4 XrXr ; 1/4 XR Y ; 1/4 Xr Y
TEST CROSS
P : XR Xr X Xr Y
G: 1/2 XR , 1/2 Xr X 1/2 Xr , 1/2 Y
F1: 1/4XR Xr ; 1/4 XrXr ; 1/4 XR Y ; 1/4 Xr Y
RED-EYED ♀
WHITE-EYED ♀
RED-EYED ♂
WHITE -EYED ♂
P: RED EYED FEMALE FROM F1 x ORIGINAL WHITE-EYED MALE
F1: Female offspring ; male offspring
(50% red; 50% white) ( 50%red; 50% white)
Conclusion: Eye-color gene is found on the X chromosome and there is no corresponding allele on the Y chromosome

11. SEX- LINKED INHERITANCE IN HUMANS
X-LINKED TRAITS IN HUMAN
(HEMOPHILIA,
DUCHENNE MUSCULAR DYSTROPHY, COLORBLINDNESS)

13. H: DOMINANT GENE FOR HEMOPHILIA h: RECESSIVE GENE FOR HEMOPHILIA
P: Homozygous normal female X hemophiliac male
X H X H X Xh Y
G: /1 XH 1/2 Xh ; 1/2 Y
F1 : 1/2 XH X h ; /2 XH Y
(carrier – female) (normal - male)

14. P: Heterozygous (carier) female X normal male
(b)
P: Heterozygous (carier) female X normal male
X H X h X XH Y
G: /2 XH , 1/2 Xh /2 XH , 1/2 Y
F1 : 1/4 XH X H ; 1/4 X H X h ; 1/4 XH Y ; 1/4 Xh Y
Homozygous carrier ♀ normal hemophiliac
normal ♀
Normal phenotyped ♀

15. P: Heterozygous (carrier) female X hemophiliac male
X H X h X Xh Y
G: /2 XH , 1/2 Xh /2 Xh , 1/2 Y
F1 : 1/4 XH X h ; 1/4 X h X h ; 1/4 XH Y ; 1/4 Xh Y
carrier ♀ hemophiliac ♀ normal hemophiliac

16. DUCHENNE MUSCULAR DYSTROPHY

17. Normal ♀ color blind♂ carrier♀ XR XR Xr Y XR Xr
COLORBLINDNESS
Normal ♀ color blind♂ carrier♀
XR XR Xr Y XR Xr
Normal ♂ colorblind ♀
XR Y X r Xr

20. The pattern of inheritance of X-linked traits;
A man inherits his X chromosome and all his X-linked traits from his mother
A woman inherits one X chromosome from her mother and one from her father
A defective X chromosome in a man is always passed to each daughter but never to a son
A defective X chromosome in a woman has a 50% chance of being passed to each son and daughter

21. Y-LINKED TRAITS IN HUMAN
A pedigree chart: Inheritance of Y-linked trait in a family
Ichtyosis hystrix (balık pulluluk)
Hair on the rim of the ears
joined 2nd and 3rd toes

22. Ichtyosis hystrix : balık pulluluk

23. Hair on the rim of the ears
Name: Radhakant Bajpai, India. Length: 13.2cm (5.2 inches)
Hair on the rim of the ears

24. A map of the human X and Y chromosomes, showing the locations of some of the genes that cause disease
Duchenne muscular dystrophy
Genes for testes
Ichtyosis hystrix
Hair on the rim of ear
Joined 2nd and 3rd toes
Hemophilia A
Colorblindness
Hemophilia B
DNA that is not organized into genes
Diabetes insipidus

25. SEX-INFLUENCED TRAITS
Inheritance of pattern baldness in humans
P: Heterozygous female X heterozygous male
Bb X Bb
G: /2 B , 1/2 b /2 B , 1/2 b
F1 :
♀ BB Bb bb
Bald normal
♂ BB Bb bb
Bald normal

26. Other examples of sex- influenced traits include;
Development of mammary glands in human
Coat patterns and milk production in cattle
Egg production in birds

27. NON-DISJUNCTION P: Vermillion- eyed female X red eyed male
6 + X r X r X XR Y
G: /1(3+ Xr) /2(3+ XR) , 1/2(3+ Y)
F1 : 1/2(6 + XR X r ) ; 1/2 (6+ Xr Y)
R= dominant red-eye gene
r = vermillion (recessive) gene

28. Nondisjunction explains exceptions in the sex–linked inheritance of eye color in Drosophila:
P: Vermillion-eyed female X red eyed male
6 + X r X r X XR Y
G: (3+ Xr Xr ) (3+0) (3+ XR) , (3+ Y)
F1 : (6 + XR Xr Xr ) (6+ XR 0) ; (6+Xr Xr Y) (6+ Y0)
R= dominant red-eye gene
r = vermillion (recessive) gene
nondisjunction
♀Vermillic
dies
♂ Red (sterile)

29. Primary nondisjunction
Secondary nondisjunction

30. The gain of one chromosome MONOSOMY The loss of a single chromosome
ANEUPLOIDY: When an organism gains or loses one or more chromosome but not a complete set
TRISOMY
The gain of one chromosome
MONOSOMY
The loss of a single chromosome
Egg (n-1) + sperm (n) (2n -1)
ex: Turner (XO)
Egg (n+1) + sperm (n) (2n + 1)
ex: Down Syndrome (45 +XX or 45 + XY)
EUPLOIDY: The condition in which complete haploid sets of chromosomes are found. If there are three or more sets, the condition is called polyploidy.(3n, 4n, 5n, 6n, 7n etc.)

33. GENE LINKAGE
Genes linked on the same chromosome are generally inherited together; they move together during meiosis (does not obey Mendel’s Principle of Independents Assortment unless crossing over occurs)

34. F2: ¾ purple-flowered and elongated pollen-grained offspring
Pure red-flowered and elongated pollen-grained pea plant
Pure purple-flowered and elongated pollen-grained pea plant
P : x
PPEE
ppee
F1: All purple-flowered and elongated pollen-grained offspring (purple-flowered and elongated pollen grain genes are dominant)
P from F1: Dihybrid purple-flowered and elongated pollen-grained parents
PpEe X
PpEe
F2: ¾ purple-flowered and elongated pollen-grained offspring
¼ purple-flowered and elongated pollen-grained offspring :

35. Expected phenotypic ratio was 9:3:3:1
But the actual ratio was found to be 3:1
Conclusion:
The genes for flower color and pollen grain shape are linked
The inheritance of two linked traits produced the same genotype and phenotype ratio in F2 as in monohybrid cross, (1:2:1) and (3:1) respectively.
Gene linkage reduces variety

36. F1: PpEe (purple elongated pollen *dominant traits)
P: PPEE x ppee
G: PE pe
F1: PpEe (purple elongated pollen *dominant traits)
are linked P E p e
P (from F1): PpEe x PpEe
G: ½ PE , ½ pe ½ PE , ½ pe
F2: ¼ PPEE, 2/4 PpEe, ¼ ppee
¾ purple elongated ; ¼ red-round
3: phenotypic ratio
1:2: genotypic ratio

37. P: PpEe X ppee PpEe X ppee
Test cross of F1
P: PpEe X ppee PpEe X ppee
G: 1/2 PE , 1/2 pe /1 pe ¼ PE, ¼ Pe, ¼ pE, ¼pe X 1/1 pe
F1 : 1/2 PpEe ; 1/2 ppee ¼ PpEe; ¼ Ppee; ¼ppEe; ¼ ppee
Gene linkage
Expected phenotypic ratio: 1:1
Actual phenotypic ratio: 7 : : 1 : 7
Recombinants due to the crossing over

38. CROSSING OVER AND RECOMBINATION

39. Ex: In Drosophila the genes for gray body (G) and normal wing (N) are dominant over the genes for black body (g) and vestigial wing (n)
In a Drosophila of genotype GgNn, 12% of the primary sex cells undergo crossing-over.
What are the types of gametes formed?
What are the expected percentages of the types of gametes formed?

40. Gray – normal : 965 Gray – vestigial: 185
Ex 2: A Drosophila dihybrid forbody color and wing shape (GgNn) is tes crossed and F1 is as follows:
Gray – normal : 965 Gray – vestigial: 185
Black – vestigial: Black – normail: 206
What is the crossing over value (recombination frequency)?

41. Chromosome Mapping Genes that are close together rarely cross-over
Genes that are farther apart will cross-over more often
Cross-over studies and cross-over values have been used to construct chromosome maps

42. Ex: Determine the order (sequence) of genes along a chromosome based on the following cross-over (recombination) frequincies.
A-B: 8 map units (m.u) A-C: 12 m.u A-D: 25 m.u
B-D: 33 m.u D-C: 13 m.u B-C: 20 m.u