This document provides an overview of genetic diseases including their history, causes, types, and examples. It discusses:
- The history of discoveries related to genetics and DNA that helped scientists understand genetic diseases.
- The main causes of genetic diseases including errors during meiosis, defects in genes passed down from parents, and spontaneous genetic mutations.
- The four main types of genetic disorders - chromosomal, single gene, multifactorial, and mitochondrial.
- Specific examples of diseases that fall under each type, such as Down Syndrome, Cystic Fibrosis, asthma, and MELAS Syndrome.
- Methods for diagnosing genetic diseases including prenatal, presymptomatic, and predictive genetic
3. • A genetic disorder is an illness
caused by one or more abnormalities
in the genome, especially a condition
that is present from birth
(congenital).
• Genetic disorders may or may not be
heritable.
• Also can be due to changes in DNA
Introduction •
4. Discovered genes are able
to change positions on
chromosomes
Both made a model of
the DNA molecule and
proved genes determie
heredity.
Barbara McClintock
Francis H.C Crick
Experimented pea
plant, and developed
principles of inheritance
Major role in
understanding the
structures of DNA & RNA
Gregor Mendel
Rosalind Franklin
Arthur Kornberg
James D. Watson
Produced DNA in a Test
tube.
• History…
@sources:google images
5. Cause 1
Cause 2
• An error during meiosis
causing defects in sex
cells
• If only one gamet is
involved in fertilization
• Nondisjunctional causes
Cause 3
• A defective gene present in
one or both parents
• Also known as hereditary
disease
• Early marriges
• Spontaneous
abortions
• Late pregnencies
• Causes
6. • Classifications
Chromosomal
disorders
Those that are caused by
numarical or structural
abnormilities of the chromosome
01
Single gene
disorder
Those that are
caused by defects
of a individual gene
02
03
04
Multifactorial
disorders
Those that are the result of
the combines effect of genetic
and enviromental factors
Mitochondrial
disorder
Those that are affected
due to mitochondrial
defects
7. 1a. Down Syndrome
› Caused by trisomy in chromosome 21
› Mental retardation, flattened face, short
stature
› High risk of cardiac anomalies, leukaemia,
cataracts and digestive blockage
› Average life expectancy is 55years
1b. Edward Syndrome
› Caused by trisomy in chromosome 18
› Skull and facial abnormalities, defected
organs
› Poor muscle tone
› Average life expectancy is 2-4 months
1. Chromosomal disorders…
8. 1c. Patau Syndrome
› Caused by trisomy in chromosome 13
› Mental and physical retardation,
have extra digit
› Cleft lip & large triangular nose
› Average life expectancy is 6 months
1d. Turner Syndrome
› Caused due to monosomy in sex
chromosome
› Webbing of neck, lack of secondary
sex characteristics, sexually
underdeveloped
› Mostly seen in females(1:3000)
@sources:google images
9. 1e. Klinefelter Syndrome
› Due to trisomy in sex chromosome (XXY)
› Tall stature, hypogonadism, lack of secondary
male characteristics
› Infertile due to reduced spermatogenesis
› Common in male
1f. Super Female
› An extra X chromosome is present
(XXX-female)
› Menstrual irregularities, slight mental
retardation
1g. Super Male
› An extra Y chromosome is present
(XYY-male)
› Usually unknown
› Tall, acne issues, speech problems
@sources:google images
10. 1h. Williams Syndrome
› Due to deletion in chromosome 7
› Delayed development, delayed
speech, moderate mental retardation
› Sunken chest, unusual appearance of
the face
1i. Cri du Chat Syndrome
› Due to deletion in chromosome 5
› Problem with larynx and nervous system
› Drooling problem, difficulty in swallowing
and sucking
@sources:google images
11. 2a. Neurofibromatosis(NF)
› It is an Autosomal dominant disease
› Mutation in chromosome number 17
› Tan spots on skin in mild cases
› Causes severe deformities, tumours
and even death
2b. Huntington’s Disease
› Repeated sequence of AGC
on chromosome 4
› Neurogenerative disorder
› Loss of balance, memory
loss, muscle jerks
› Onset is between 35-45
years
2. Single Gene Disorders…
@sources:google images
12. 2c. Cystic Fibrosis
› An autosomal recessive disorder
› Mutation in chromosome 7
› Difficulty in breathing, lung
infection
› Thick mucous develops in lungs
› Most common lethal genetic
disorder
2d. Tay Sachs Disease
› An autosomal recessive disorder
› Mutation in HEXA gene
› Gradual paralysis, loss of
nervous functions
› Heterozygote carrier are
resistant to Tb.
@sources:google images
13. 2e. Colour Blindness
› Sex link recessive disorder
› Unable to see colour in normal
way
› Can’t distinguish between
colours generally green, red
and blue
› Mostly in males
2f. Haemophilia
› Sex link recessive disorder
› Caused by inheritance of one
recessive gene on X or both X
› Blood doesn't clot
› Risk of sever bleeding from common
injuries
› Common in males
@sources:google images
14. 2h. Sickle Cell Anaemia
› Abnormality in haemoglobin
› Cell becomes sickle shaped and clog
blood vessels
› Poor circulation of blood, anaemia,
jaundice
› Heterozygote carriers are resistant to
malaria
› Mutation in chromosome 11
2g. Severe Combined Immunodeficiency (SCID)
› Mutation in the SCIDX1 gene in X chromosome
› Defects in immune system
› Chronic skin infection, diarrhea, hepatitis
@sources:google images
15. 3. Multifactorial diseases…
3a. Asthma
› Common chronic inflammatory disease
› Inflammation in asthmatic airways
› Wheezing, chest tightness, difficulty in breathing,
coughing, etc are symptoms of asthma
3b. Autoimmune Disease
› Arises from abnormal immune response to own
body
› Destroys normal body tissues
› leads to more hypersensitive reactions
@sources:google images
16. 3c. Cancer
› Uncontrolled growth and spread of
abnormal cells
› Change in bowel habits or bladder
functions
› Unusual bleeding, coughing
› Indigestion and difficulty in swallowing
3d. Heart Diseases
› Fatty deposits of cholesterol- Atherosclerosis
› Hypertension also leads to heat failure
› Occurs when coronary arteries that supply the
heart muscles became blocked
› Uncomfortable pressure, fullness, chest
discomfort, squeezing pain
@sources:google images
17. 4. Mitochondrial Disorders…
4a. MELAS Syndrome
› Due to mutation in mitochondria
› Occurs in brain, blood gets too acidic
› Most common inherited mitochondrial
disease
› Vomiting, migraine droopy eyelids, muscle
weakness
4b. Renal Oncocytoma
› Tumour of the kidney made of oncocytes
› Tumour is densely packed with mitochondria
› Presence of blood in urine, abdominal mass
@sources:google images
18. • Diagnosis…
o Prenatal diagnosis- Diagnosis of genetic disease or condition in the developing fetus
o Presymptomatic genetic testing- Can tell if a person with a family history for a
genetic disease but does not have symptoms.
o Preimplantation studies- Used only in in-vitro fertilization to diagnose a genetic
disease in an embryo before it is implanted into the mother's uterus.
o Predictive genetic testing- Can tell you the chances that a healthy person with or
without a family history of a certain disease might develop that disease
19. Earliest evidence of
hereditary genetic disorder
discovered
A
B
A genetic marker linked
to Huntington disease was found
on chromosome 4 in 1983, making
Huntington disease, or HD, the
first genetic disease
• Facts…
@sources:google images
