This document discusses pedigree analysis, which is used to determine the mode of inheritance of genetic traits and diseases in humans. Pedigree analysis involves collecting phenotypic data from multiple generations and constructing a pedigree chart using symbols. Careful analysis of the pedigree chart can reveal whether a trait is inherited dominantly or recessively. The document also outlines different patterns of inheritance including autosomal dominant/recessive, sex-linked dominant/recessive, Y-linked, and mitochondrial inheritance and provides examples for each. Pedigree analysis is an important tool in genetic research and counseling.

1. PEDIGREE ANALYSIS
Dr. Valli Nachiyar C
Professsor, Biotechnology
Sathyabama Institute of Science and Technology

2. Pedigree Analysis
• Nature of gene (dominant, recessive or codominant) can be found
out after analyzing the results from controlled crosses
• But this is not possible with humans and species with long
generation time
• So an important alternate approach is Pedigree Analysis
 Phenotypic data from several generation will be collected
 A chart with different symbols will be prepared (Pedigree Chart)
 Careful analysis should be carried out which will help to
determine whether that particular trait is dominant or recessive

3. Pedigree Charts
• diagrams that show the phenotypes and/or genotypes for a
particular organism and its ancestors.
• used in human families to track genetic diseases, they can
be used for any species and any inherited trait.
• used to determine the mode of inheritance of a particular
disease or trait, and to predict the probability of its
appearance among offspring.
• Pedigree analysis is therefore an important tool in both basic
research and genetic counseling.

4. Mating between relative
Consanguineous
marriage
PEDIGREE SYMBOLS
Unaffected female
Sex unspecified
Affected Individuals
Deceased
Proband
Mating
Carrier
Dizygotic Twins
Monozygotic Twins
Unaffected male

5. INHERITED PATTERNS (SINGLE GENE DISEASES)
• Autosomal dominant
• Autosomal recessive
• Sex – linked dominant / X – linked dominant
• Sex – linked recessive / X – linked recessive
• Y linked inheritance
• Mitochondrial inheritance

6. Autosomal Dominant Pedigree
• Involves a Dominant allele on non-sex chromosomes / Autosomes
• Do not Skip Generations
• Affected parents can give rise to unaffected children –
Unaffected parents can give rise only to unaffected children
• Males and Females affected equally
• No Carriers – If the allele is present – only affected individual
• Huntington’s disease, Neurofibromatosis , Polycystic kidney disease,
Achondroplasia, Familial hypercholesterolemia

7. Aa Aa
Aa Aa
Aa
Aa Aa
aa
aa
aa
aa aa aa

8. Autosomal Recessive Pedigree
• Involves a Recessive allele on non-sex chromosomes /
Autosomes
• Skip Generations
• Unaffected parents can give rise to affected children
• Males and Females affected equally
• Presence of Carriers
• Cystic fibrosis, Sickle cell anemia, Tay-Sachs disease,
Phenylketonuria (PKU)

9. By Madibc68 - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=79625482
https://commons.wikimedia.org/wiki/File:Wiki_Drawing_-_Autosomal_Recessive_(2).svg
aa
aa
Aa Aa
Aa/AA
AA
Aa aa aa
Aa Aa/AA
Aa
Aa

10. Sex Linked / X – linked Dominant Pedigree
• Involves a Dominant allele on X chromosomes
• Do not Skip Generations
• Females more frequently affected
Daughters of affected Father will be affected
• Never passed on to Father to Son
• Hypophosphatemic rickets, Ornithine transcarbamylase
deficiency, Oral-facial-digital syndrome type I , Fragile X
syndrome.

11. XaXa XA
XAXa
XA XAXa XA
XA
XA
XAXA /
XaXA
XA Xa
XAXa
XAXA

12. Sex Linked / X – linked Recessive Pedigree
• Involves a Recessive allele on X chromosomes
• Skip Generations
• Males more frequently affected
• Sons of affected Mother will be affected
• Presence of Female carriers
• Hemophilia A, Red Green colour blindness,
Duchenne muscular dystrophy

13. By Madibc68 - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=79625479
https://commons.wikimedia.org/wiki/File:Wiki_Drawing_-_X-
Linked_Recessive_(1).svg
XaXa
XaXa
XaXa
XAXa XAXa
XAXa
Xa
Xa
Xa
Xa
Xa
XA
XA

14. XAXA Xa
XAXa
XA XAXa XA
XA
XA
XAXA /
XaXA
XA Xa
XAXa
XAXA

15. Y Linked Pedigree
• Involves an allele on the Y chromosome
• Do not Skip Generations
• Only males are affected
• Passed on from Father to Son
• Hodgkin Disease (Pseudoautosomal), Retinitis
Pigmentosa, Sertoli cell-only syndrome, Nonobstructive
Spermatogenic Failure
• https://rep.bioscientifica.com/view/journals/rep/139/2/303.xml

16. By Madibc68 - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=79625485
https://commons.wikimedia.org/wiki/Category:Pedigree_charts#/media/File
:Wiki_Drawing_-_Y-Linked_(1).svg

17. Mitochondrial Inheritance
• Involves an allele on the Mitochondria DNA (mtDNA)
• Do not Skip Generations
• Passed on from Mother to all off springs (Since only
mother contributes cytoplasmic contents to her
offprings
• Exercise intolerance, Kearns Sayre Syndrome, Leber’s
hereditary optic neuropathy

18. By Madibc68 - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=79625483
https://commons.wikimedia.org/wiki/Category:Pedigree_charts#/media/File:Wiki_Dr
awing_-_Mitochondrial.svg

19. REFERENCES
https://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel9.htm#:~:text=Scientists
%20have%20devised%20another%20approach,inheritance%20of%20genes%20in%20hu
mans.&text=Once%20phenotypic%20data%20is%20collected,are%20some%20rules%20
to%20follow.
Dr. Todd Nickle and Isabelle Barrette-Ng -
https://bio.libretexts.org/Bookshelves/Genetics/Book%3A_Online_Open_Genetics_(Nick
le_and_Barrette-
Ng)/05%3A_Pedigrees_and_Populations/5.03%3A_Inferring_the_Mode_of_Inheritance
https://www.ncbi.nlm.nih.gov/books/NBK132145/#:~:text=The%20basic%20laws%20of
%20inheritance,understanding%20patterns%20of%20disease%20transmission.&text=The
re%20are%20five%20basic%20modes,%2Dlinked%20recessive%2C%20and%20mitoch
ondrial.