“Single gene disorder is defined as diseases that occur due to the mutations in the single gene that ultimately form non-functional gene”.

1. Presented by: Shumaila Riaz
0827-BH-Z-18
Presented to: Dr. Andleeb Batool

2. 
 “Single gene disorder is defined as diseases that
occur due to the mutations in the single gene that
ultimately form non-functional gene”.
 It is also named as Mendelian disorders, unifactorial
or monogenetic disorders.
 Thousands of diseases in human are result of single
gene mutations. As they are genetic disorders, it
means they pass from parents to offspring.
What are single gene
disorders?

3. 
 Autosomal Disorders
 Autosomal Dominant
 Autosomal Recessive
 X-Linked Disorders
 X-linked Recessive
 X-linked Dominant
Categories

4. 
 Dominant: in which only one defected or mutated gene in parents
is needed to cause disease in offspring
 Recessive: both genes are affected and then pass on next
generation
 Examples:
 Autosomal Dominant Disorders
 Huntington Disorder
 Neurofibromatosis type 1
 Marfan Disorder
 Autosomal Recessive Disorders
 Beta thalassemia
 Sickle cell anemia
 Cystic fibrosis
 Phenylketonuria
Autosomal Disorders

5. 
 Dominant: common in females as female contains two X
chromosomes
 Disorders:
 Rett Syndrome
 X-linked lissencephaly
 Renal phosphate transport
 Fragile X syndrome
 Recessive: mostly in males as male contain only one X-
chromosome
 Disorders:
 Hemophilia A
 Red-Green Color Blindness
X-linked Disorders

6. 
 For this disorder only one mutated gene copy is
necessary for the transmission of disorder. The
chance for inherited mutation is 50%. This disorder
happens in the heterozygous condition.
 There are some common disorders that are:
 Huntington Disorder
 Neurofibromatosis type 1
 Marfan Disorder
Autosomal Dominant
Disorders

7. 
 This is progressive brain disorder in which connection
between brain and movements disturbs, nerve cells that
carry messages breakdown and results in disturbance of
person’s thinking ability
 In 1800s, a physician named ‘George Huntington” first
explained this disorder hence this disorder is named after
him. It is caused by the defection in gene on chromosome
number 4. This is “dominant” defect, means any offspring
that carry defected gene from parents will be a patient of
Huntington’s disorder. In 1993, defective gene is observed
that is main reason for Huntington disease.
Huntington’s disease

8. 
 The age for appearance of this disorder varies from
early as 2 years late as 80 years old.
 Major symptoms are
 uncontrolled movements of hands, face, head and
legs.
 Loss of thinking and reasoning skills, mood swings
 inability to control anger and depression
 There is no proper cure for this disorder.
Symptoms

9. 

10. 
 Connective tissues disability to anchor organs is the
main disorder of Marfan syndrome. Heart, eyes,
blood vessels and skeleton are badly affected in this
syndrome.
 Genes coding proteins that help in providing
elasticity to body, any mutation in them leads to
Marfan syndrome
 Common symptoms are extremely long arms,
fingers and legs, breastbone outward, long and
crowded teeth, weak eyesight, and mostly flat feet.
Marfan syndrome

11. 

12. 
 In this genetic disorder nervous system became
inactive and the growth of nerve cells retarded. It
forms tumors on nerves, which may be of benign or
malignant tumor. Family history is the biggest risk
factor for this disorder as NF1 and NF2 are
autosomal dominant disorders and there are 50 %
chances for offspring to carry this disorder.
Neurofibromatosis

13. 
 There are three types of neurofibromatosis which are
 Neurofibromatosis type 1 (NF1): it mostly happens in
childhood or early ages and mostly symptoms appear at the
time of birth. Mutation on gene at chromosome # 17 causes this
type 1 disorder. It is more common type.
 Neurofibromatosis type 2 (NF2): in this type, benign tumor
forms near ear that progresses slowly causing loss of hearing.
Merlin gene present at chromosome # 22 that suppresses tumor
formation, any mutation in it, causes NF2 type disorder.
 Schwannomatosis: affect mostly after age of 20, benign tumor
forms at cranial or spinal nerves. Tumor not progress as in NF2.
Two genes named as SMARCB1 and LZTR1 are the reason for
third type of neurofibromatosis.
Types and Causes

14. 
 NF1: in this case light brown colored spots appear on
skin, freckling, tiny nodules on eye, abnormal bone
formations, large sized head, disability to learn
things properly and tumors on optic nerves appears.
 NF2: with the passage of time loss of hearing occurs,
poor balance, pain, loss of sight and constant
headache.
 Schwannomatosis: constant pain in body parts for
long period, weakness and loss of balance.
Symptoms

15. 

16. 
 These types of disorders can only appear if an individual carry
both mutated alleles and if these transfer to offspring it must
cause disease in them. As in autosomal recessive pedigree there
is chance for generation skip, so it is difficult to detect it by
seeing family disorders. Heterozygous conditions are carriers
while homozygous recessive are affected ones.
 25% chance that one child will be affected one while 2/3rd of
their siblings will be carrier.
 Disorders:
 Beta thalassemia
 Sickle cell anemia
 Cystic fibrosis
 Phenylketonuria
Autosomal Recessive
Disorders

17. 
 It affects secretory glands in which mostly mucus
and sweat glands are majorly affected. Lungs,
pancreas, liver, intestine and sex organs are affected
in this inherited disorder
 Cystic Fibrosis gene is present on chromosome
number 7 that encodes cystic fibrosis
transmembrane regulator (CFTR) named protein.
Any abnormality in CFTR leads to CF in which there
is abnormality in the chloride channels in cells
Cystic Fibrosis

18. 
 Excessive abnormal thick and sticky mucus is
formed due to mutation in CFTR; this thick mucus
then ultimately blocks the air passage and causes
shortness of breath. Chronic lung infections are main
symptoms.
 The digestive enzymes from pancreas cannot pass
through pancreas due to blockage of pancreas by this
thick and sticky mucus causes disability to absorb
fats and proteins
Symptoms

19. 

20. 
 Mutation in phenylalanine hydroxylase (PAH) gene
leads to the inability of the body to proper use of essential
amino acid phenylalanine. As there is more production of
phenylalanine than its usage, this leads to mental
retardation and change in behaviors.
 Gene mutations or alterations in the phenylalanine
hydroxylase cause PKU and it leads to the low
metabolism resulting increase in toxic substances in
body and blood. Phenylalanine hydroxylase is an enzyme
that hydrolyzes phenylalanine to tyrosine that is
necessary for body’s normal functioning. Both affected
parents pass mutated genes to child for this disorder
Phenylketonuria

21. 
 Symptoms of PKU may be mild or severe, most
severe case of PKU is named as Classic PKU, while
mild or less severe is known as Variant PKU. Some
common symptoms are mental retardation, seizures,
hand trembling, inability to grow normal, and most
common is musty odor of breath.
Symptoms

22. 

23. 
 As females have two X chromosomes while males have
one X and one Y chromosome. Due to this X-linked
dominant disorders are common in females than in males,
and some diseases are such as that they only affect
females. There is no father to son transmission. But if
males are affected they are severely affected. These
disorders are:
 Rett Syndrome
 X-linked lissencephaly
 Renal phosphate transport
 Fragile X syndrome
X-linked Dominant Disorders

24. 
 In this disorder child’s learning, thinking and health affected in
mostly females but if males caught this disorder they will
experience more severe cases.
 FMR protein is produced by the FMR1 gene on X chromosome
helps in the nerve communication. If there is any mutation in
this gene then it will retard brain growth and child will face
difficulties in communication and understanding things
properly.
 The most important and distinguish factor in Fragile X
syndrome is that affected people have more copies of DNA
with CGG code. Like in normal people this segment repeats for
5-40 times but in these patients this repetition comes for more
than 200 times and it cause severe conditions.
Fragile X syndrome

25. 
 People with this disorder face variety of symptoms
from mild to severe. Some common symptoms are
loss of thinking, trouble in walking or sitting because
of loss of nerve connections. They do not make eye
contact and are extremely sensitive to light or
sound.
 Their appearance change from normal children in
such a way as they have abnormal large head, ear
and forehead with flat feet
Symptoms

26. 

27. 
 It is genetic disorder that mostly affects the nervous
system in most of female. After birth, it takes two
years to diagnose this disorder.
 If there is mutation on X chromosomes it will cause
Rett syndrome. However it’s pattern and exact
reason is not known but if affected females more
than males but the severity rate is high in males.
 There are no sign n symptoms at the first 6 month of
baby so it is difficult to diagnose it, but after the age
of 12-18 months this disease progresses by showing
symptoms
Rett Syndrome

28. 

29. 
 Disorders due to the mutations on X chromosomes
are known to be X-linked recessive disorders. As
female has two copies of X chromosomes, if one copy
is mutated one and one is non-mutated, and then
female will be carrier of this disorder but not an
affected one. While in case on male, he will be the
affected one.
 There are some X-linked recessive disorders which
are:
 Hemophilia A
 Red-Green Color Blindness
X-linked Recessive
Disorders

30. 
 In this condition blood clotting factor affected in such a
way that if blood starts to flow due to absence of clotting
gene it will be difficult to stop blood from flowing. It is
genetic disorder and run in family but 1/3rd of cases are
reported in which there is no previous family history.
 Protein factor VIII is absent in Hemophilic A patients, this
factor is essential for stop bleeding.
 Symptoms may vary from mild to severe. Some common
symptoms are severe bleeding after any surgery or injury
or after birth. It further leads to cancer
Hemophilia A

31. 

32. 
 Deuteranopia or red-green color blindness is the most
common type of the color blindness in which affected one
face difficulty in seeing different shades of red and green
color. OPN1LW, OPN1MW and OPN1SW are the genes
that play role in seeing three primary colors in normal
person.
 Due to genetic mutations in X chromosome this disorder
can occur. Red-green color blindness is due to the
mutations or defect in the OPN1LW which is red
pigmented (protanopia) cones and OPN1MW is green
pigmented cones (deuteranopia).
 These affected patients face trouble in differentiating
shades of red and green pigments.
Red-Green Color
Blindness

33. 

34. 
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References

35. 