The document provides an overview of sex-linked inheritance diseases, detailing how genetic traits are passed through X and Y chromosomes. It explains types of inheritance including X-linked dominant and recessive conditions, with examples such as fragile X syndrome and color blindness. The document also discusses Y-linked inheritance, describing its rarity and specific conditions like Swyer syndrome and male infertility.

1. Sex linked
inheritance
diseases
Submitted by
DURGADEVI B

2. MODE OF INHERITANCE
• It’s the manner in which particular genetic trait or
disorder is passed from one generation to next
generation
• TYPES OF INHERITANCE:
• Autosomal (Dominant/recessive)
• Sex-linked (Dominant/recessive)
• Mitochondrial inheritance.
• In humans there are 23 pairs of chromosomes
(22 pairs CHROMOSOMES + XY CHROMOSOMES)
NOTE:XY=SEX CHROMOSOMES & 22 = AUTOSOMES

3. SEX LINKED INHERITANCE
• Sex Linked Inheritance involves genes
are located on either the X or the Y
chromosomes.
• Females can be homozygous or
heterozygous for genes carried on the X
chromosomes.
• Males can be only hemizygous.
• Females have only X chromosomes.
• Males have both X&Y chromosomes.
• XX=FEMALES XY=MALES

4. TYPES:
• There are 2 types
•X linked inheritance
•x linked dominant inheritance
•x linked recessive inheritance
•Y linked inheritance

5. X LINKED DOMINANT INHERITANCE
• Dominant gene is carried on the X- gene
• Males – get their X- chromosomes from their
mother.
• Females - get their X chromosomes from both
their parents.
Best examples
•Fragile X syndrome
•Incontinentia pigmenti

6. Examples:
• If mother is carrier of the mutated gene
• 50% of the son or daughter will be affected.
• 50% of the son or daughter will be normal.
• If father is carrier of the mutated gene
• 100% of his daughter will have disorder.
• 0% of his son will have disorder.
• If both parents are a carrier of the mutated gene
• 100% of his daughter will have disorder.
• 50% of his son will have disorder.
• 50% of his son will be affected or normal.

8. Fragile X syndrome
• Its genetic condition involving changes in part of the X
chromosomes
• Most common form of inherited intellectual disability in boys
CAUSES
• Caused by gene called FMR1
• Boys & girls both are affected.
• But boys have only one X chromosomes so they affected
more.

9. Cont..
• SYMPTOMS
• Flat feet
• Large body size
• Long face
• Soft skin
• Test
• In females excess of shyness may be the only
sign only the disorder
• Genetic testing
• Other names
• Martin-bell syndrome
• Marker X syndrome

10. X LINKED RECESSIVE INHERITANCE
• Affected most exclusively in males
• Affected sons are usually born to unaffected mothers
• Approx.1/2 of carrier mothers sons are affected
• It is never passed from father to son.
• Mostly females are the carriers
• Example:
•Color blindness
•Haemophilia

11. • In this case son is totally
affected
• Daughter is mostly
carrier
• In some cases both are
become unaffected

12. Color blindness
• Color blindness is the inability to see some colors in the
usual way.
• Most types are caused by a gene located on the X
chromosomes
• Red green colorblindness is the most common type
SYMPTOMS
• Trouble seeing colors and brightness of color in usual way.
• Inability to see the difference between the shades of color.
• Rapid , side to side eye movements(nystagmus)

13. Cont..
TEST FOR COLOR BLINDNESS
•Ishihara test
•Normal color vision see at “8”
•Colorblindness people don’t see
anything
•HRR(hardy, rand & rattler) Color test for
red-green color test
Other names
Color deficiency

14. In this case son is
totally affected.
Daughter is mostly
carrier.
In some cases both
are become un
affected.

15. Y LINKED IN HERITANCE
• Holandric inheritance
• Y- chromosomes is small does not contain the many genes.
• Y linked diseases are very rare.
• Its occur between fathers to son.
• In humans hariy ears apper to be inheritaed through the Y
chromosomes.
Examples
• Swyer syndrome
• Y chromosomes in fertility

16. • Its occur between fathers to
son
• Never transmitted from
father to daughter or even to
grand daughter i.e.,
transmitted from male to
male
• Only sons are affected

17. Y chromosomes infertility
• It refers to a males inability to cause pregnancy in a fertile
female.
• Its is due to deficiencies in the semen & semen quality.
CAUSES
• DRUGS AND ALCOHOL
• Strenuous riding , bike race , horse racing
• Obesity
TEST
• Semen Analysis
• Ultrasonography

18. Contd…
• PREVENTION
• Avoid smoking
• Avoid liquor
• Wearing a protective cup while playing foot ball,
cricket etc
• TREATMENT
• Intrauterine insemination(IUI).
• In vitro fertilization (IVF).
• Intracytoplasmatic sperm injection.
• Hormonal therapy.

19. DIFFERENCE B/W
X LINKED INHERITANCE Y LINKED INHERITANCE
Characters are inherited by genes are located in X
chromosomes.
Characters are inherited by genes are located in Y
chromosomes alone.
Inherited in both males & females Inherited only in males
Never transmitted from father to son but from father
to grand son
Never transmitted from father to daughter or even to
grand daughter i.e., transmitted from male to male
Eg: color blindness in humans. Eg : hairy pinna of the ear, Y chromosomes infertility