This presentation gives an overall view of the patterns of inheritance and the chromosomal abnormalities.

1. {
Occurrence, pattern of
inheritance and chromosomal
abnormalities
Presentation By :
Asha

2.  The method by which genes are inherited from one generation to
another is called inheritance.
 Pattern of inheritance is the manner in which gene is transmitted
down the generations.
 Inheritance can be categorized according to the chromosome
from which the trait comes
Inheritance ?

3.  Mendelian pattern of inheritance
 Non-Mendelian pattern of inheritance.
Classification of chromosomes :

4.  They follow the Mendel’s Principles of Inheritance i.e
1. Principle of Dominance
2. Principle of Segregation
3. Principle of Independent Assortment.
Autosomal dominant Inheritance:
If the phenotype associated with a given allele of a
gene is observed when an individual has only one
copy, the allele is said to be autosomal dominant.
Mendelian Inheritance :
Pattern of Inheritance

5. Examples of diseases associated :
Huntington's disease
Myotonic Dystrophy
Familial Hypocholesteremia

6.  If the phenotype associated with a given version of a gene is observed only
when an individual has two copies, the allele is said to be autosomal
recessive.
 The phenotype will be observed only when the individual is homozygous
for the allele concerned.
 An individual with only one copy of the allele will not show the phenotype,
but will be able to pass the allele on to subsequent generations.
 As a result, an individual heterozygous for an autosomal recessive allele is
known as a carrier.
Autosomal recessive Inheritance:

7. Examples of diseases associated:
Sickle cell anemia
Phenylketonuria
Cystic fibrosis

8.  Inheritance of genes present on sex ( X or Y )
chromosomes.
 X linked inheritance:
X linked dominant disease : Fragile x syndrome
X linked recessive disease : Hemophilia , Fabrys
disease
Y linked inheritance: Y linked infertility
Sex-linked Inheritance :

9.  The inheritance pattern do not follow Mendel’s principles
 Two alleles may have a different relationship than the simple
dominant-recessive relationship.
1. Codominance:
Codominance occurs when both alleles
are expressed equally in the phenotype
of the heterozygote.
Non-Mendelian inheritance
patterns

10. 2. Incomplete dominance:
Incomplete dominance occurs when the phenotype of the offspring is
somewhere in between the phenotypes of both parents; a completely
dominant allele does not occur.
Eg : Sickle cell anemia.
Snapdragon flowers.
3. Multiple alleles:
A set of three or more alleles of a gene, only two of which can be a
present in a diploid organism.
Eg :ABO blood grouping

11. 3. Mitochondrial inheritance:
4. Mitochondrial inheritance :
Only offspring of the affected mother are affected
Eg :
1. Myoclonic epilepsy and ragged red
fibre disease (MERRF)
- Deafness, dementia, seizures.
2. Laber’s hereditary optic
neuropathy (LHON)
- Sudden bilateral blindness

12. Chromosomal abnormalities occur when there is a defect in a chromosome,
or in the arrangement of the genetic material on the chromosome.
Chromosomal Abnormalities
A chromosome abnormality, is a missing, extra, or irregular portion
of chromosomal DNA. It can be from an atypical number
of chromosomes or a structural abnormality in one or more chromosomes.

13. Types :
1. Numerical Aberrations.
2. Structural Aberrations.
Hyperploidy
Numerical Aberrations
Aneuploidy
Tetrasomy, 2n+2
Trisomy, 2n+1
Hypoploidy
Monoploidy, n
Diploidy, 2n
Euploidy
Nullisomy, 2n-2
Monosomy, 2n-1
Polyploidy, >2n

14. Edward’s Syndrome – Trisomy
18
Examples :
Turner Syndrome – 47, X
Klinefelter Syndrome – 47,
XXY
Jacob Syndrome – 47, XYY
Down Syndrome - Trisomy 21

16. Deletions : Loss of a portion of a chromosome.
• Prader-Willi (PWS) and Angelman syndrome (AS) are
distinct neurogenetic disorders caused by
chromosomal deletions on chromosome 15.
• Cri du chat syndrome : Deletion in Chromosome 5

17. Insertion :
Fragile X Syndrome: Insertion of over 200 CGG repeats in a
gene on X chromosome.
Huntington Disease: CAG repeat insertion on Chromosome 4.
Duplications :
Charcot-Marie-Tooth disease type 1A
which may be caused by duplication of the
gene encoding peripheral myelin protein
22 (PMP22) on chromosome 17
- Loss of muscle tissue and touch sensation
in various parts of the body.

18. Translocation:
• In a reciprocal translocation, segments from two different chromosomes have
been exchanged.
• Eg : Chronic myeloid Leukemia, Ch 22.
• In a Robertsonian translocation, an entire chromosome has attached to
another at the centromere; these only occur with chromosomes 13, 14, 15, 21
and 22.
Reciprocal translocation Robertsonian translocation

19. Inversion :
Eg :Hemophilia is an
example for inversion
mutation .
i.e inversion in F8
gene on the X
chromosome.

20. Thank you