Pedigree Analysis

Explains how to analyze pedigree

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 D eceased Pro band Mating Carrier Dizygotic Twins Monozygotic Twins Unaffected male

5. IN HERITED PATTERNS (SINGLE GENE DISEASES) Autosomal dominant A utosomal 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. X a X a X A X A X a X A X A X a X A X A X A X A X A / X a X A X A X a X A X a X A X A

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 X a X a X a X a X a X a X A X a X A X a X A X a X a X a X a X a X a X A X A

14. X A X A X a X A X a X A X A X a X A X A X A X A X A / X a X A X A X a X A X a X A X A

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_Drawing_-_Mitochondrial.svg

19. REFERENCES https://www.ndsu.edu/pubweb/~mcclean/plsc431/mendel/mendel9.htm#:~:text=Scientists%20have%20devised%20another%20approach,inheritance%20of%20genes%20in%20humans.&text=Once%20phenotypic%20data%20is%20collected,are%20some%20rules%20to%20follow. Dr. Todd Nickle and Isabelle Barrette-Ng - https://bio.libretexts.org/Bookshelves/Genetics/Book%3A_Online_Open_Genetics_(Nickle_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=There%20are%20five%20basic%20modes,%2Dlinked%20recessive%2C%20and%20mitochondrial.