non mendelian inheritance

1. PATTERNS OF
INHERITANCE
BY:
MRS.KEERTHI SAMUEL
ASST.PROFESSOR
VIJAY MARIE CON

2. PATTERNS OF INHERITANCE
 Observations of the way traits, or characteristics, are passed from
one generation to the next in the form of identifiable phenotypes
probably represent the oldest form of genetics.
 The various ways in which genes are transmitted are
 Autosomal Dominant
 Autosomal Recessive
 X-linked dominant
 Y-linked Recessive

3. I.AUTOSOMAL DOMINANT
Affected parent
Normal
parent
Gamete
A a
a
Aa aa
a
Aa aa
• Males and females are affected equally
• Affected individual has affected parent unless caused by fresh
mutation.
• Half the children are heterozygous
• Affected parent will posses defective gene.
• Unaffected children of affected parents will have unaffected
children. Ex: breast and ovarian cancers
• Alzheimer's , Huntington's disease, hypercholesteremia

4. II.AUTOSOMAL RECESSIVE INHERITANCE
Heterozygous Parent
A/a
Hetero
zygous
Gamete
A a
A
AA Aa
CARRIER
a
Aa
CARRIER
aa
• Males and females are affected equally
• Affected individual has unaffected parents who are
heterozygous for the trait.
• There is 1 in 4 chance that any child of 2 unaffected
heterozygous parents will be affected.
• 2 affected parents will have affected children exclusively
• PKU,SCA,Albinism, Cystic fibrosis

5. III.X-LINKED DOMINANT INHERITANCE
NORMAL MOTHER
Affected
father
Gamete
X X
XA
XAx XAx
Y
XY XY
AFFECTED MOTHER
NORMAL
FATHER
Gamete
XA X
X XAx Xx
Y
XAY XY

6.  Affected individuals have an affected parent
 All the daughters but none of the sons of an affected male will be affected.
 Half the sons and half the daughters of an affected female will be affected.
 Normal children of an affected parent will have normal offspring .
 There are no carriers.
 Ex: fragile X syndrome, ADHD, MR
III.X-LINKED DOMINANT INHERITANCE

7. IV.Y-LINKED RECESSIVE INHERITANCE
NORMAL MOTHER
Affected
father
Gamete
X X
XA
Xax
(carrier)
Xax
(carrier)
Y
XY XY
CARRIER MOTHER
NORMAL
FATHER
Gamete
XA X
X Xax
Carrier daughter
Xx
Y
XAY
Affected son
XY

8.  Affected individuals are principally males
 Affected individuals have unaffected parents
 Half of female siblings of an affected will be carriers.
 Ex: Hemophilia A & B, Duchenne Muscular dystrophy
IV.Y-LINKED RECESSIVE INHERITANCE

9. NON MENDELIAN INHERITANCE
Mosaicism Imprinting
Prader willi
Angelman
syndrome
Triplet repeats
Fragile X
syndrome
Myotonic
dystrophy
Mitochondrial
inheritance

10. MOSAICISM
 It refers to the presence of 2 or more distinct cell lines, one
normal and one abnormal . This was first recognized in
chromosomal disorders.
 Ex: segmental Neurofibromotosis (NF) - only certain areas of
body were affected. Cells from affected areas were shown to
have the gene coding of NF’s.
 Cells from unaffected areas had the normal gene. As his gonads
were involved, he passed the NF gene onto his children who
were in turn fully affected.

11. IMPRINTING
 It refers to modification of the gene as it is transmitted
through father and mother.
 Ex: Prader Willi , Angleman, Obesity, Intellectual
disability.
 Both conditions are due to deletion of a chromosomal
segment.
 If the deleted chromosome 15 is paternal in origin-PWS
 If its maternal in origin -AMS

12. TRIPLET REPEATS
 It is a condition where 3 base repeats CTG,CGG,CAG are
abnormally repeated in a genome.
 This triplet repeats are found close to the beginning within or close
to the end of the gene.
 The function of these repeated DNA sequences is not clearly
defined.
 As they are passed onto subsequent generation it can undergo
expansion in size and result in various genetic diseases.
 Ex: fragile X syndrome: CGG is repeated. Normally 6-40 repeats
are present. Unaffected carriers have 50-200 pairs affected have
200-1000 repeats.

13. MITOCHONDRIAL INHERITANCE
 Mitochondria are power houses of the cell which provides
energy by oxidative phosphorylation.
 The number of mitochondria varies from species to species and
even among cells of different tissues.
 The genectic conditions due to abnormal mitochondrial DNA are
very rare .
 This follows vertical pattern which means only mother can
contribute her mitochondria to the zygote.
 Ex: Lactic acidosis