genetics

1. Inheritance patterns
Recessive: expressed only when both
chromosomes of a pair carry mutant alleles at
a locus (2 mutant copies)
Dominant: expressed when one chromosome
of a pair carries a mutant allele at a locus (1
mutant copy)

2. • Autosomal: on any of the other 22
chromosome pairs.
• Sex-linked: on the X or Y chromosomes

3. Autosomal Recessive Inheritance
• Autosomal recessive traits are only expressed
in individuals who carry two mutant alleles
inherited from each parent.
• Autosomal recessive traits usually arise in
children of phenotypically normal parents.

4. Genotype and phenotype correlation with gene locus
for an autosomal recessive trait

6. Segregation of an autosomal recessive trait in a
pedigree

7. Autosomal recessive: increased incidence of parental
consanguinity

8. Autosomal recessive inheritance
• Usually parents are heterozygous carriers
• Affected individuals are usually born to
unaffected parents
• Affected children are homozygous for mutant
gene
• In most autosomal recessive diseases males and
females are equally likely to be affected
• Carrier couple has a 1 in 4 chance of having
affected offspring
• There is an increased incidence of parental
consanguinity

9. Oculocutaneous Albinism
• Lack of pigmentation
• Fair skin and hair
• Decreased visual acuity
• Lack of stereoscopic vision
• Mutations in the gene encoding Tyrosinase
(lack of Melanin) on ch11q14.3
• Long term sun exposure may predispose skin
cancer known as melanoma.

10. Oculocutaneous Albinism
This affects both male
and female and is
apparent from birth .
Research indicates that
OCA type1 occurs in 1 per
40,000 and OCA type2 1in
15,0000.
OCA type 3 and OCA type
4 have not yet found.
OCA type 2 is less severe
than OCA type 1.

11. Cystic Fibrosis
• Cystic Fibrosis: a lethal autosomal recessive
genetic disease
• Caused by deletion of 3 bases(delta F 504
phenylalanine ) on chromosome 7(CFTR gen
on ch7q31.2).
• Common among Caucasians 1 in 20 are
carriers
• One in 400 Caucasian couples will be both
carriers of CF – 1 in 4 children will have it.

12. • CF disease affects transport in tissues – mucus is
accumulated in lungs, causing infections.
• Fluid in lung and potential respiration failure are
common.

13. Cystic Fibrosis
• IF two parents carry the recessive gene of
Cystic Fibrosis (c), that is, they are
heterozygous (C c), one in four of their
children is expected to be homozygous for cf
and have the disease:
C C = normal
C c = carrier, no symptoms
c c = has cystic fibrosis

14. Gaucher Disease
• Gaucher Disease is a rare autosomal recessive
genetic disease. It causes lipid-storage
disorder (lipids accumulate in spleen, liver,
kidney, brain and bone marrow)
• It is the most common genetic disease
affecting Jewish people of Eastern European
ancestry (1 in 500 incidence; rest of pop. 1 in
100,000)

16. Symptoms include:
• Hepatomegaly
• Spleenomegay
• Anemia
• Leucopenia
• Thrombocytopenia
• Neurological disorder
• Osteoporosis

17. Autosomal Dominant Inheritance
• Autosomal dominant traits are expressed in
heterozygous or homozygous individuals.
• An affected person usually has at least one
affected parent
.

18. Genotype and phenotype correlation with gene locus
for an autosomal dominant trait

19. Pedigree illustrating autosomal dominant transmission

21. Autosomal dominant
• Expressed in heterozygous or homozygous individuals
• Affects an individual of either sex
• Transmitted by either sex
• An affected person usually has at least one affected
parent
• Transmitted to 50 % of offspring

22. Osteogenesis Imperfecta Type I
• Osteogenesis Imperfecta is an autosomal
dominant genetic disorder that mainly causes
deficient production of the protein collagen
leading to abnormal bone matrix.
• Muations in COL1A1on chromosome 17
(17q21.31) or COL1A2 on chromosome
7(7q22.1) lead to reduced amounts of normal
collagen

23. Osteogenesis type I is a genetic disorders that
mainly affect the bones. It results in bones
that break easily.
The severity may be mild to severe.Other
symptoms may include a blue tinge to
the whites of the eye, short height, loose
joints, hearing loss, breathing problems

24. Huntington Chorea
• The disease affects a person's ability to think,
talk, and move (brain disorder).
• The disease destroys cells in the basal ganglia,
the part of the brain that controls movement,
emotion, and cognitive ability.
• HD is caused by a mutation in a gene on the
short arm chromosome 4.

26.  Most people who have the disease start to see
symptoms between the ages of 30 and 50 (but
symptoms can appear earlier or later in life).
 Symptoms include poor memory, depression
mood swings, lack of coordination, twitching
or other uncontrolled movements, and
difficulty walking, speaking, and/or
swallowing.