GENETIC VARIATION AND ITS ROLE IN HEALTH / PHARMACOLOGY.pptx

GENETIC VARIATION AND ITS ROLE IN HEALTH / PHARMACOLOGY

1. GENETIC VARIATION and its ROLE IN HEALTH / PHARMACOLOGY ANAGHA K B KH.PH.P2MPG23002

2. Contents Introduction Genetic variation Different sources of genetic variation Role in health and pharmacology References

3. Genetic variation is the difference in DNA among individuals or the differences between populations among the same species The diversity of genetic traits within a population or species. Genetic variation is what makes us all unique, whether in terms of hair colour , skin colour or even the shape of our faces. Individuals of a species have similar characteristics but they are rarely identical, the difference between them is called variation . a result of subtle differences in our DNA. Single Nucleotide Polymorphism (SNPs) : most common type of genetic variation . Genetic variation permits flexibility and survival of population in adverse conditions, more resistant to diseases, also it creates diversity. It can also cause some undesired effects like genetic disorder, diseases, etc. Genetic Variation

4. Sources of Genetic variation Mutation Gene flow Sexual reproduction

5. MUTATION is changes in the DNA sequence. Mutations can result from errors in DNA replication during cell division, exposure to mutagens or viral infection .

6. GERMLINE MUTATION Germline mutations are congenital genetic mutations in germ cells that originate from sperm or ovum and are generally incorporated into every cell of the offspring's body. result in offspring with a genetic condition Eg ; cancer, trisomy 21, H untington’s disease

7. 2. GENE FLOW the transfer of genetic material from one population to another . In humans gene flow usually comes about through the actual  migration  of human populations, either voluntary or forced.

8. 3. SEXUAL REPRODUCTION Sexual reproduction involves fusion of haploid female gamete(egg cell) and haploid male gamete produce tremendous genetic variation in offspring Sexual reproduction results in genetic variation among siblings Meiosis results in newer combinations of parental genotypes by crossing over thus generating unique genotypes.

9. CROSSING OVER Genetic recombination  is the exchange of genetic material between different organisms which leads to production of offspring with combinations of traits that differ from those found in either parent. Crossover happens during prophase I stage of meiosis. It produces recombination genes by interchanging the corresponding segments between non-sister chromatid the chromatids breaks, exchange and rejoin and produce genetic variation.

10. TYPES OF GENETIC VARIATIONS Single Nucleotide Polymorphisms Insertions and Deletions (Indels) Structural Variations Copy Number Variations (CNV) Variable Number of Tandem Repeats (VNTRs) Chromosomal Rearrangements

11. 1. Single Nucleotide Polymorphism SNPs are naturally occurring genetic variations within the human genome. involves single nucleotide differences between individuals of the same species. About 10 million SNPs are present in the human genome ( one SNP every 1200 bases) Distribution: SNPs is not evenly distributed throughout genome, certain SNP-rich and SNP-poor region are present. Duffy blood group system has clinical significance ; protects against malaria.

12. SNPs Non-coding SNPs Coding SNPs Non-synonymous Synonymous/silent polymorphism Alters amino acid code No effect on encoded amino acid code

13. 2. Insertions and Deletions (Indels) Deletion or insertion of between 1 to 1000 nucleotides extra or missing DNA nucleotides in the genome Insertion/deletion variants are less frequent than SNVs but can sometimes have a larger impact on health and disease Eg : 3-base pair deletion (DF508) in the coding region of the CFTR gene is the most common cause of cystic fibrosis. can result in diseases like cystic fibrosis due to disruptions in gene function.

14. Tandem Repeats are short stretches of nucleotides that are repeated multiple times and are highly variable among people.  also known as microsatellites Chromosomes contains such short nucleotide stretches repeated, ranging from a few times to hundreds of times. Tandem repeats that contain more than 50 nucleotides are considered structural variants Historically, tandem repeats have been used for building maps of the human genome and DNA profiling in forensics applications.  3. Structural Variations structural differences in the DNA, originated mainly due to chromosomal rearrangements – deletion, duplication, novel sequence insertion, or inversion.

15. COPY NUMBER VARIATIONS When a structural variant reflects differences in the total number of nucleotides involved, it is called a C opy Number Variant (CNV).

16. Technologies for detecting Genetic variation :

17. Applications of Genetic Variations Screening for Genetic Diseases Pharmacogenomics Biological markers Forensic Technologies

18. MUTATION POLYMORPHISM Mutation is a permanent alteration of a nucleotide sequence of a gene Polymorphism is the presence of more than one allele at a particular locus in a particular population A physical event A population attribute A single base pair change in the nucleotide sequence of a gene is called a point mutation A single base pair change in the nucleotide sequence is called a single nucleotide polymorphism Sickle cell anemia, hemophilia, cystic fibrosis, Klinefelter syndrome, and Turner syndrome are results of mutations Human gender, and ABO blood group are a result of polymorphism

19. ROLE IN HEALTH/ PHARMACOLOGY GENE REPLACEMENT AND GENE ADDITION replacement of the sickle globin gene (βS) with a normal copy of the gene (βA). From a knock-in mouse model of Sickle cell disease e mbryonic stem cells was collected and reprogramed into iPS cells. Gene replacement was done [ β S allele r eplaced with normal β A allele] Corrected iPS cells are differentiated into hematopoietic progenitors in vitro Animals produced high levels of normal human hemoglobin ( HbA ) . .

20. 2. DNA and RNA targeting and delivery method Therapeutic targeting of Huntington’s disease Genetic Cause of HD: CAG repeat expansions in the HTT gene. HTT gene encodes the huntingtin protein. Caused by aberrant expansion of repeating DNA sequence in HTT gene involuntary jerky movements Difficulty in coordinating voluntary movements Cognitive impairment Mood fluctuations Methods to reduce mHTT levels in brain. Promote mRNA degradation – Antisense Oligonucleotides(ASOs) Inhibit mRNA translation – using non coding RNAs – RNAi Technology Mutant allele inactivation – CRISPR/Cas9 Technology

21. ASOs Oligonucleotides Short, synthetic ,single stranded DNA sequence . ASOs ; allele specific ASOs , non- allele specific ASOs Tominersen ASOs mHTT mRNA Hybridized complex Ribonuclease H- mediated Hydrolysis Destruction of mRNA 40% reduction in mHTT level in CSF – Clinical trials

22. RNAi Technology (RNA interference Technology ) Suppress the translation of mHTT by targeting its mRNA Small non- coding RNAs are used 80% reduction in HTT mRNA-preclinical studies Amt-30 ; a nonallele-specific miRNA coupled to an adeno-associated viral vector (AAV5) for delivery.

23. CRISPR/Cas 9 Technology Clustered Regularly Interspaced Short Palindromic Repeats Is a genome editing treatment approach RNA – guided nuclease Cas9 - used for allele specific genome editing To inactivate the mutant allele without harming the normal one .

24. MUTATION IN CCR5 CCR5 gene encodes chemokine receptors CCR5 Location : p21.3 region of human chromosome 3 CCR5 is a co-receptor for macrophage-tropic strains of HIV-1. CCR5 RECEPTOR binds with HIV HIV infection Mutant allele Δccr5 provides strong resistance to HIV infection The identification of naturally occurring CCR5 mutation(Δ32bp deletion) has allowed scientists to address CCR5 as a promising target to prevent HIV. A mutant allele CCR5 Δ32bp encodes a non-functional truncated protein that is not transported to cell surface and hence not expressed and thus prevents viral invasion. CCR5 expression can also be prevented through gene editing techniques

25. Reference : Molecular Pharmacology: From DNA to Drug Discovery . John Dickenson et .al The Pharmacological basis of Therapeutics ,Goodman and Gilman’s Molecular Cell Biology , Harvey Lodish Arnold Berk Chris A. Kaiser Monty Krieger Anthony Bretscher Hidde Ploegh Angelika Amon Kelsey C. Martin Elsevier PubMed Gene replacement therapy for sickle cell disease and other blood disorders – article Therapeutic targeting of Huntington's disease: Molecular and clinical approaches – article

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