for assigment Teknologi pendidikan Pensyarah:Md Yusoff Daud Aplikasi Student: Ummu Sulaim Mohammad A138175

1. SEX LINKAGE
Characters which are associate more
with one gender
© 2007 Paul Billiet ODWS

2. Characters associated with
gender
Anhiorotic ectodermal dysplasia
 Small teeth, no sweat glands, sparse
body hair
 Occurs primarily in men
 Never transmitted from father to son
 Unaffected daughters may pass the
condition onto their sons (the
grandsons)
© 2007 Paul Billiet ODWS

3. Sex linkage explained
http://nobelprize.org/nobel_prizes/medicine/articles/lewis/index.html
 Thomas Hunt Morgan in The Fly Room!
(Columbia University 1910)
 Fruit Flies (Drosophila melanogaster)
© 2007 Paul Billiet ODWS

4. The case of the white-eyed
mutant
Character Traits
Eye colour Red eye (wild type)
White eye (mutant)
P Phenotypes
Wild type (red-eyed) female x White-eyed male
F1 Phenotypes All red-eyed
Red eye is dominant to white eye
© 2007 Paul Billiet ODWS

5. Hypothesis
A cross between the F1 flies should give us: 3 red
eye : 1 white eye
F2 Phenotypes Red eye White eye
Numbers 3470 782
82% 18%
So far so good
© 2007 Paul Billiet ODWS

6. An interesting observation
F2 Phenotypes Red- Red- White- White-
eyed eyed eyed eyed
males females males females
Numbers 1011 2459 782 0
24% 58% 18% 0%
© 2007 Paul Billiet ODWS

7. A reciprocal cross
Morgan tried the cross the other way round
white-eyed female x red-eyed male
Result
All red-eyed females and all white-eyed males
This confirmed what Morgan suspected
The gene for eye colour is linked to the X
chromosome
© 2007 Paul Billiet ODWS

8. A test cross
Phenotypes F1 Red-eyed female x White-eyed male
Expected result
50% red-eyed offspring: 50% white-eyed offspring
Regardless of the sex
Observed Results
Red-eyed Red-eyed White-eyed White-eyed
Males Females Males Females
132 129 86 88
© 2007 Paul Billiet ODWS

9. Genetic diagram for sex linked genes
Character Trait Alleles
Eye colour Red eye R
White eye r
Genotypes Phenotypes
XRXR
XRXr
XrXr
XRY
XrY
© 2007 Paul Billiet ODWS

10. Genetic diagrams for sex linked genes
Character Trait Alleles
Eye colour Red eye R
White eye r
Genotypes Phenotypes
XRXR Red-eyed female
XRXr Red-eyed female
XrXr White-eyed female
XRY Red-eyed male
XrY White-eyed male
© 2007 Paul Billiet ODWS

11. P Phenotypes Wild type x White-eyed
(red-eyed) male
female
Genotypes XRXR XrY
Gametes XR XR Xr Y
Fertilisation Xr Y
XR XRXr XR Y
XR XRXr XR Y
© 2007 Paul Billiet ODWS

12. F1 Phenotypes Red-eyed x Red-eyed
female male
Genotypes XRXr XR Y
Gametes XR Xr XR Y
Fertilisation XR Y
XR XRXR XRY
Xr XRXr XrY
© 2007 Paul Billiet ODWS

13. F2 Phenotypes Females Males
Red- White- Red- White-
eyed eyed eyed eyed
Expected All None 50% 50%
Observed 2459 0 1011 782
This gene has its LOCUS on the X-chromosome
It is said to be SEX-LINKED
© 2007 Paul Billiet ODWS

14. X-linked genes
 In sex linked characteristics the reciprocal crosses
do not give the same results
 For X-linked genes fathers do not pass the mutant
allele onto their sons
 For X-linked genes fathers pass the mutant allele
onto their daughters who are carriers
 Carrier mothers may pass the allele onto their sons
(50% chance)
 Females showing the trait for an X-linked mutant
allele can exist but they are rare
 Female carriers may show patches of cells with
either trait due to X chromosome inactivation
© 2007 Paul Billiet ODWS

15. Tortioseshell Cats are Female
© 2007 Paul Billiet ODWS

16. Daltonism = Red-Green
Colourblindness
Normal vision Colour blind simulation
http://www.onset.unsw.edu.au/issue1/colourblindness/colourblindness_print.htm
© 2007 Paul Billiet ODWS

17. LIGHT
The retina
Optic
nerve
fibres Ganglion layer
Bipolar cells
(neurones)
Synapse layer
Rod cell
Nuclear layer
Inner segments packed with
Cone
mitochondria
cell
Rod and cone outer
segments
© 2007 Paul Billiet ODWS

18. PHOTORECEPTION
VISION COLOUR MONOCHROME
PHOTORECEPTOR CONES: RODS: max. sensitivity
red sensitive 560nm 505nm
green sensitive 530nm
blue sensitive 420nm
DISTRIBUTION Concentrated in the fovea Widely spread over whole
retina, absent from fovea
PIGMENTS 3 proteins controlled by 3 genes. RHODOPSIN = Retinol
Red and green pigments sex linked (Vit A) + Opsin (a protein).
Blue pigment autosomal (Chr.7) Also called visual purple
BLEACHING Slow Fast (very sensitive)
REGENERATION Slow (after images in bright light, Fast
complementary colours)
USE Daylight vision Night vision
Light adaptation 5 min Dark adaptation 20 min or
© 2007 Paul Billiet ODWS wear red goggles!

19. Blood Clotting and Haemophilia
A simplified scheme of the important steps
Damaged blood vessels
Prothrombin Thrombin
Inactive enzyme Active enzyme
Fibrinogen Fibrin = Clot
Globular protein Fibrous protein
© 2007 Paul Billiet ODWS

20. Contact with collagen fibres
in blood vessels
Factor III
Thromboplastin released
from blood vessel walls
Factor XII (inactive) → Factor XII (active)
Factor XI (inactive) → Factor XI (active)
Factor IX (inactive) → Factor IX (active)
Antihaemophilic factor B
Factor VIII
Antihaemophilic factor A
Factor X (inactive) → Factor X (active)
Ca2+ ions and blood platelets
Factor II (inactive) → Factor II (active)
Vitamin K precursor Prothrombin Thrombin
Factor I (inactive) → Factor I (active)
© 2007 Paul Billiet ODWS Fibrinogen Fibrin

21. The antihaemophilic factors
 The blood clotting reaction is an enzyme
cascade involving Factors XII, XI, IX, X and II
 Each of these enzymes are proteases that cut
the next protein in line
 Other factors including proteins like Factor
VIII are essential as coenzymes
© 2007 Paul Billiet ODWS

22. Heamophilia
 About 85% of haemophiliacs suffer from
classic haemophilia (1 male in 10 000)
 They cannot produce factor VIII
 The rest show Christmas disease where they
cannot make factor IX
 The genes for both forms of haemophilia are
sex linked
 Haemophiliacs do clot their blood slowly
because there is an alternative pathway via
thromboplastin
© 2007 Paul Billiet ODWS