Genetics of metabolic diseases

• What is a genetic mutation?

  A genetic mutation is a change in the nucleotide sequence of DNA, which can involve substitution, insertion, or deletion of one or more base pairs
• What are the two main types of causes for genetic mutations?

  Genetic mutations can be caused by spontaneous/natural events or induced by external agents
• Give examples of spontaneous causes of genetic mutations

  Examples include replication errors, tautomerization, deamination, and depurination.
• Name a chemical mutagen that intercalates between DNA bases

  Ethidium bromide
• How do alkylating agents cause mutations?

  Alkylating agents add alkyl groups to nucleobases, which can alter their pairing properties and speed up depurination
• What are inborn errors of metabolism (IEMs)?

  IEMs are genetic disorders that result from mutations affecting metabolic enzyme functions, leading to the inability to properly metabolize substances
• What is Phenylketonuria (PKU) and which gene is affected?

  PKU is an autosomal recessive disorder caused by mutations in the PAH gene, leading to a deficiency in phenylalanine hydroxylase
• What is the consequence of untreated PKU?

  Untreated PKU can lead to mental retardation, organ damage, and unusual posture due to high levels of phenylalanine in the blood
• How is von Gierke disease diagnosed?

  Von Gierke disease is diagnosed by full gene sequencing of the G6PC gene
• What enzyme deficiency is associated with McArdle disease?

  McArdle disease is associated with a deficiency in muscle glycogen phosphorylase (PYGL gene)
• What is the Guthrie test used for?

  The Guthrie test is used to screen newborns for PKU by measuring phenylalanine concentrations in blood spots
• Describe one method for detecting known mutations using PCR

  One method is ARMS (Amplification Refractory Mutation System), which uses allele-specific primers to test for the presence of a mutation
• What are the steps involved in the PCR process?


  The steps are denaturation of DNA, annealing of primers, and extension by DNA polymerase
• What is the principle behind Single-Strand Conformational Polymorphisms (SSCP)?

  SSCP detects mutations by identifying conformational changes in single-stranded DNA fragments under non-denaturing conditions
• What are the two main strategies for gene therapy?

  The two main strategies are ex vivo gene therapy, where cells are modified outside the body and then reintroduced, and in vivo gene therapy, where vectors encoding the corrective gene are injected directly into the body
• How is Familial Hypercholesterolaemia (FH) diagnosed?

  FH is diagnosed through genetic testing for mutations in the LDLR, APOB, and PCSK9 genes
• What biochemical treatment is used for Glycogen Storage Diseases (GSD)?


  Treatment involves supplying the missing metabolite and managing diet to control metabolite levels
• What enzyme activity is measured to diagnose Tay-Sachs disease?

  Beta-hexosaminidase A enzyme activity is measured
• What type of mutation typically causes Tay-Sachs disease?

  Tay-Sachs disease is usually caused by mutations in the HEXA gene
• What is the primary treatment strategy for Phenylketonuria (PKU)?

  The primary treatment strategy for PKU is a low-phenylalanine diet to prevent the buildup of phenylalanine in the blood
• What is a tautomeric shift in the context of DNA?

  A tautomeric shift is a spontaneous structural alteration in DNA bases, where bases switch between different forms (e.g., keto to enol), leading to mispairing during DNA replication
• How do deaminating agents cause mutations?

  Deaminating agents remove amino groups from DNA bases, which can result in base substitutions, such as cytosine being converted to uracil
• What is depurination, and what effect does it have on DNA?

  Depurination is the loss of a purine base (adenine or guanine) from the DNA molecule, resulting in an abasic site that can lead to mutations during DNA replication
• Describe the role of intercalating agents in mutagenesis

  Intercalating agents insert themselves between DNA bases, causing frameshift mutations by inducing insertions or deletions during DNA replication
• What is the consequence of a mutation in the PAH gene?

  A mutation in the PAH gene results in Phenylketonuria (PKU), where the enzyme phenylalanine hydroxylase is deficient, leading to an inability to metabolize phenylalanine
• What are the symptoms of McArdle disease?

  Symptoms of McArdle disease include muscle weakness, cramps, and limited ability to perform strenuous exercise due to the absence of muscle glycogen phosphorylase
• How is Tay-Sachs disease screened?

  Tay-Sachs disease is screened by measuring beta-hexosaminidase A enzyme activity in the blood and through molecular genetic testing of the HEXA gene
• What dietary restriction is necessary for managing PKU?

  Individuals with PKU need to follow a low-phenylalanine diet to prevent the buildup of phenylalanine in the blood
• How is Familial Hypercholesterolaemia (FH) treated?

  FH is treated with statins, which decrease LDL cholesterol production and increase LDL receptor production to enhance cholesterol uptake from the blood
• What is the function of glucose-6-phosphatase, and what happens when it is deficient?

  Glucose-6-phosphatase converts glucose-6-phosphate to glucose in the liver. Its deficiency, as seen in von Gierke disease, leads to severe hypoglycemia and glycogen accumulation in the liver
• What is the purpose of the Guthrie test in newborn screening?

  The Guthrie test is used to detect elevated levels of phenylalanine in newborns, indicating PKU
• What does PCR stand for, and what is its purpose?

  PCR stands for Polymerase Chain Reaction. It is used to amplify specific DNA sequences to detect mutations or for further genetic analysis
• What is the principle behind the Amplification Refractory Mutation System (ARMS)?

  ARMS uses allele-specific primers to amplify only the wild-type or mutant allele, allowing for the detection of specific mutations
• Describe the process of Single-Strand Conformational Polymorphisms (SSCP)


  SSCP involves denaturing DNA to single strands and detecting mutations by observing conformational changes in single-stranded DNA fragments through non-denaturing gel electrophoresis
• What is the difference between ex vivo and in vivo gene therapy?

  Ex vivo gene therapy involves modifying cells outside the body and then reintroducing them, while in vivo gene therapy involves directly delivering vectors encoding the corrective gene into the patient's body
• What is the main advantage of using viral vectors in gene therapy?

  Viral vectors are efficient at delivering genes into cells and ensuring gene expression, despite potential risks of toxicity and immune responses
• What are the common types of viral vectors used in gene therapy?

  Common viral vectors include adenovirus, adeno-associated virus (AAV), retrovirus, and lentivirus
• How does CRISPR/Cas9 work in genome editing?

  CRISPR/Cas9 targets and cleaves specific DNA sequences, allowing for the replacement or disabling of defective genes and potential gene correction via homology-directed repair
• What are the risks associated with CRISPR/Cas9?

  Risks include the potential for off-target mutations in genome regions with similar sequences to the target site
• What are liposomes, and what are their advantages in gene therapy?

  Liposomes are lipid bilayer vesicles used to deliver DNA to cells. They are non-toxic but often inefficient in DNA transfer and target specificity