Genetic Disorders

Genetic disorders may be Mendelian and Chromosomal disorders.
example- Haemophilia, Sickle cell anemia, THalessemia, Colour Blindness, Phenylketonuria, Cystic fibrosis, Turner Syndromes etc

1. GENETIC DISORDERS By- Dr R K Upadhyay PGT, Biology

2. GENETIC DISORDER Mendelian disorders alteration or mutation in the single gene transmitted to the offspring can be traced in a family by the pedigree analysis Examples - Haemophilia , Cystic fibrosis, Sicklecell anaemia , Colour blindness, Phenylketonuria , Thalassemia Chromosomal disorders due to absence / excess / abnormal arrangement of one or more chromosomes Failure of segregation of chromatids in cell division cycle results in the gain / loss of a chromosome(s ), called A neuploidy Down’s Syndrome Klinefelter’s Syndrome Klinefelter’s Syndrome

3. Mendelian disorders SEX LINKED X LINKED RECESSIVE Colour Blidness Haemophilia AUTOSOMAL Sickle-cell anaemia Phenylketonuria Thalassemia

4. Colour Blidness sex-linked recessive ( X- linked) Unable to discriminate in red and green colour . Male - 8 % Female - 0.4 % Cause- faulty cones

5. Genotype Phenotype X X Normal X C X Carrier X C X C Diseased colour blind X Y Normal X C Y Diseased colour blind

6. For practice Mother- carrier father – diseased offsprings -- ????

7. Haemophilia Sex linked recessive ( X- Linked) disease Non stop bleeding due to one defected gene responsible for blood clotting . The Queen Victoria was a carrier of the disease.

8. Genotype Phenotype X X Normal X H X Carrier X H X H Diseased Haemophilic X Y Normal X H Y Diseased Haemophilic

9. For practice father – normal mother – deseased offspring ----??????

10. Sickle-cell anaemia Autosome linked recessive trait The disease is controlled by a single pair of allele, HbA and HbS . Cause- substitution of Glutamic acid ( Glu ) by Valine (Val) at the sixth position of the beta globin chain of the hemoglobin molecule. The shape of the RBC from biconcave disc to elongated sickle shaped

11. The mutant hemoglobin molecule undergoes polymerization under low oxygen tension causing the change in the shape of the RBC from biconcave disc to elongated sickle like structure

12. Sickle cell anemia / symptoms and effect - swelling  of the hands and feet - Fatigue or extreme tiredness - jaundice . - delayed growth - episodes of  pain

13. Genotype Phenotype Hb A HB A Normal Hb A Hb B Carrier Hb B Hb B Diseased Sickle cell anemia

14. For practice father – carrier mother – deseased offspring ----??????

15. Phenylketonuria This inborn error of metabolism. Autosomal recessive trait . The affected individual lacks an enzyme that converts the amino acid phenylalanine into tyrosine . Phenylalanine is accumulated and converted into phenylpyruvic acid in brain results in mental retardation . These are also excreted through urine because of its poor absorption by kidney.

16. Thalassemia autosome -linked recessive blood disease reduced rate of synthesis of one of the globin chains ( alpha and beta chains) that make up haemoglobin . formation of abnormal haemoglobin resulting into anaemia which is characteristic of the disease .

17. TYPES Alpha Thalassemia - production of Alpha globin chain is affected. It is controlled by two genes HBA1 and HBA2 on chromosome 16 of each parent. Beta Thalassemia - production of beta globin chain is affected . It is controlled by a single gene HBB on chromosome 11 of each parent. Thalassemia - quantitative problem sickle-cell anaemia - qualitative problem Thalassemia

18. Cystic fibrosis Autosomal recessive disorder of infants. Cause - recessive autosomal allele chromosome 7 It produces a defective glycoprotein. formation of thick mucus in skin, lungs, pancreas, liver eand other secretory organs.

19. Cystic fibrosis

20. Chromosomal Disorders Due to absence or excess or abnormal arrangement of one or more chromosomes Aneuploidy - Failure of segregation of chromatids during cell division cycle results in the gain or loss of a chromosome(s ) Polyploidy - increase in a whole set of chromosomes Down’s Syndrome Klinefelter’s Syndrome Turner’s Syndrome

21. Down’s Syndrome CAUSE – trisomy of chromosome number 21 First desribed by - Langdon Down (1866). Features - short statured with small round head , furrowed tongue, partially open mouth Palm is broad with palm crease. Physical, psychomotor and mental development is retarded .

22. Klinefelter’s Syndrome Cause - Karyotype of 47, XXY. Features - masculine development, however , the feminine development ( development of breast, i.e., Gynaecomastia ) Such individuals are sterile .

23. Turner’s Syndrome Cause – Karyoytpe 45 with X0 Features - Such females are sterile as ovaries are rudimentary. lack of other secondary sexual characters

24. THANK YOU