helpful to 12th standard students

1. By Jitesh A
Daunde

2. Normal Night blind

4. Haemophilia
-Is a hereditary blood disorder.
-Blood fails to clot or clot very
slowly.
-Person carry recessive gene for
this trait.
-Recessive X- linked disorder.
-Has deficiency in clotting factor
(factor VIII and IX).
-Even minor injury cause
continuous bleeding.
-Hence called Bleeder’s disease.

5. Sex Normal Haemophilic Carrier
Male XHY XhY ------
Female XHXH XhXh XHXh
Genotype of different individuals for haemophilic gene can be
represented as follows
Gene for normal clotting is- XH
Gene for haemophilia is – Xh
Both genes are located on non- homologous region of X chromosome

6. 1st Possibility

7. 2nd Possibility

8. 3rd Possibility
Haemophilia follows Criss-cross inheritance,
it transmit from father to his grandson through daughter

9. Sex determination
In humans, there are two varieties of sex
chromosomes: a larger X chromosome and
a smaller Y chromosome
The SRY gene on the Y chromosome
codes for a protein that directs the
development of male anatomical features
Females are XX (Homomorphic), and
males are XY (Heteromorphic)
Each ovum contains an X chromosome,
while a sperm may contain either an X or a
Y chromosome
Other animals have different methods of
sex determination

10. Parents
or
Sperm
or
Egg
Male Female
44 
XY
44 
XX
22 
X
22 
Y
22 
X
44 
XX
44 
XY
(a) The X-Y system
H
U
M
A
N
Mechanism of sex determination
Gamete formation in humans
Spermatogenesis Oogenesis
Human Male
Heterogametic–
Produce 2 types of
sperms
1st- 22 autosomes + X
2nd - 22 autosomes + Y
Human Female
Homogametic–
Produce only one
types of sperms
22 autosomes + X

11. Thus,
Father is responsible for sex of the child and not the mother
In honey bees
It is depend on number of sex chromosomes received by an individual.
Called as Haplo-diploid sex determination system.
Fertilized egg develops in to female (May be queen or worker )
have 2n= 32 number of chromosomes
Unfertilized egg develops in to male.
means by Parthenogenesis .
have n= 16 number of chromosomes
** Drones produce sperm by mitosis.
Figure 15.6
32
(Diploid)
16
(Haploid)
The haplo-diploid system

12. In birds
Sex determination is ZW-ZZ type.
 In this males are homogametic have ZZ sex chromosomes.
 Females are heterogametic with ZW pairs of sex chromosomes.
Figure 15.6
76 
ZW
76 
ZZ
(The Z-W system

13. Mendelian disorder
Thalassimia
It is a group of autosomal disorder.
 Characterized by decreased synthesis of alpha and beta globin chain of HbA.
Heamoglobine- Conjugated protein made by A and B chain.
each chain consist alpha and beta globin subunits.
Two types of thalassimia
1. Alpha thalassimia- caused by deficient synthesis of alpha globin subunit
2. Beta thalassimia- caused by deficient synthesis of synthesis of beta globin
subunit
Alpha globin chain is coded by gene lies on 16th chromosome. And
Beta globin chain is coded by gene lies on 11th chromosome.
Clinically person is suffer from
Anemia- inability to synthesize Hb
Jaundice
Variation in size and shape of RBC etc

14. Massive blood transfusion is needed.
It is quantitative abnormality of polypeptide globin chain synthesis.