Week 3 General principles Flashcards

Question

Describe factors responsible for genetic variations in populations

Answer 1

1. Mutation: Changes in the DNA sequence that introduce new genetic variants. These are the primary source of new alleles. 2. Gene Flow (Migration): The movement of individuals or their genetic material between populations, introducing new alleles and increasing genetic diversity. 3. Genetic Drift: Random fluctuations in allele frequencies due to chance events, especially in small populations. This can lead to the loss or fixation of alleles over time. 4. Sexual Reproduction: The recombination of genes during meiosis (crossing over) and the random assortment of chromosomes, leading to unique genetic combinations in offspring. 5. Natural Selection: The differential survival and reproduction of individuals based on their genetic traits. This can increase the frequency of advantageous alleles and decrease the frequency of harmful alleles. 6. Non-Random Mating: When individuals preferentially mate with others based on specific traits, such as inbreeding or assortative mating, it can affect allele frequencies.

Answer 2

Aneuploidy: refers to abnormal number of chromosomes, either an extra chromosome (trisomy) or missing one (monosomy). These abnormalities can affect autosomes (non-sex chromosomes) or sex chromosomes. Trisomy 21 (down syndrome) Causes: extra copy of chromosome 21 Symptoms: intellectual disability, characteristic facial features, heart defects and increase risk of leukemia and Alzheimer's disease Karyotype: 47, XX +21 or 47,XY +21 Trisomy 18 (Edwards syndrome) Extra copy of chromosome 18 Symptoms: Severe developmental delay, heart defects, clenched hands, low birth weight, rocker feets, short life expectancy Trisomy 13 (Patau syndrome) Cause extra copy of chromosome 13 Symptoms: Severe intellectual disability, cled lip/palate, heart defects and typically death within first year. Karyotype 47 xx +13 or 47XY +13 Sex chromosome aneuploidy Klinefelter syndrome (XXY): Causes: males with an extra X chromosomes, Symptoms: hypohonadism, infertility, taller stature and mild developmental delay Karyotype: 47 XXY Turner syndrome (X0) Causes: Females with only 1 X chromosome (monosomy X) Symptoms: short stature, infertility, heart defects, lack of secondary sexual characteristics and puberty. Karyotypes 45,X

Answer 3

Translocation Definition: A segment of one chromosome is transferred to another chromosome. o Types: Reciprocal Translocation: Two chromosomes exchange segments. Robertsonian Translocation: Fusion of two acrocentric chromosomes (common in Down syndrome). Example: Chronic Myelogenous Leukemia (CML), caused by a Philadelphia chromosome (t(9;22)). 2. Deletion Definition: A segment of a chromosome is lost. Result: Loss of genetic material, leading to disorders. Example: Cri-du-chat syndrome, caused by a deletion on chromosome 5 (46,XX,5p-). Inversion Definition: A chromosome segment is reversed end to end. Result: No loss of genetic material, but it can affect gene function or result in problems during meiosis. Example: Pericentric inversion of chromosome 9 can be benign or lead to fertility issues. 4. Ring Chromosomes Definition: A chromosome forms a ring structure due to the deletion of the ends of the chromosome, followed by the fusion of the broken ends. Result: Loss of genetic material at the ends and potential gene imbalances. Example: Ring chromosome 14 causes severe developmental delay and other health issues.

Answer 4

Multifactorial inheritance refers to traits or diseases caused by the combined influence of multiple genes and environmental factors. Unlike Mendelian inheritance, where one or two genes dictate the outcome, multifactorial traits are influenced by a range of genetic and environmental interactions. Influential Factors 1. Multiple Genes: Several genes contribute to the trait or disease, each having a small effect. 2. Environmental Factors: Lifestyle, diet, exposure to toxins, and other environmental factors can modify the expression of the genetic predisposition. 3. Gene-Environment Interaction: The interaction between genetic predisposition and environmental influences can increase or decrease the risk of developing a disease. Examples of Multifactorial Inheritance Diseases 1. Heart Disease: Caused by a combination of genetic susceptibility (e.g., cholesterol metabolism genes) and environmental factors (e.g., diet, exercise). 2. Type 2 Diabetes: Genetic factors (insulin resistance genes) combined with environmental factors (obesity, sedentary lifestyle). 3. Cleft Lip and Palate: A complex condition with genetic and environmental risk factors (e.g., maternal smoking). 4. Hypertension: Both genetic predisposition and environmental factors like salt intake and stress contribute to the condition. Key Points Polygenic: Multifactorial traits often involve multiple genes. Risk Prediction: The risk of inheriting multifactorial diseases is higher when close relatives are affected, but inheritance patterns are less predictable than Mendelian traits.

Answer 5

1. Polymerase Chain Reaction (PCR) Purpose: Amplifies specific DNA sequences to detect mutations or genetic variants. Use: Diagnosis of genetic disorders, detecting infectious agents, and genetic fingerprinting. 2. Gel Electrophoresis Purpose: Separates DNA, RNA, or proteins based on size and charge. Use: Identifying genetic mutations, checking DNA purity, and allele analysis. 3. DNA Sequencing Purpose: Determines the exact sequence of nucleotides in a DNA sample. Use: Identifying genetic mutations, studying genetic variation, and gene mapping. Techniques: Sanger sequencing (traditional) and next-generation sequencing (NGS, high throughput). 4. Chromosome Analysis (Karyotyping) Purpose: Visualizes chromosomes to detect large-scale chromosomal abnormalities (e.g., trisomies, deletions, translocations). Use: Diagnosis of chromosomal disorders like Down syndrome and Turner syndrome. 5. Fluorescence In Situ Hybridization (FISH) Purpose: Uses fluorescent probes to bind specific DNA sequences on chromosomes. Use: Detecting chromosomal abnormalities and gene localization. 6. Microarray Analysis Purpose: Detects the expression of thousands of genes simultaneously or identifies copy number variations. Use: Studying gene expression profiles and identifying genetic mutations linked to diseases. 7. Genomic Profiling Purpose: Analyzes an individual's entire genome using various techniques like NGS. Use: Personalized medicine, disease risk assessment, and identifying gene-environment interactions. Conclusion Genetic analysis involves various methods that help in identifying mutations, understanding inheritance patterns, and diagnosing genetic conditions. These tools are essential in research, clinical diagnostics, and personalised medicine.

Answer 6

Blotting Techniques Blotting techniques are used to transfer and detect specific molecules (DNA, RNA, or proteins) from a sample to a membrane, followed by visualisation using specific probes or antibodies. They are commonly used in research and diagnostics to identify genetic mutations, gene expression patterns, or protein markers. Types of Blotting Techniques 1. Southern Blotting (DNA) Purpose: Detects specific DNA sequences. Method: DNA is digested, separated by gel electrophoresis, transferred to a membrane, and hybridized with a labeled probe. Use: Diagnosing genetic diseases (e.g., detecting gene deletions, mutations) and identifying specific genetic markers. 2. Northern Blotting (RNA) Purpose: Detects specific RNA sequences and measures gene expression. Method: RNA is separated by gel electrophoresis, transferred to a membrane, and hybridized with a labeled probe. Use: Analyzing gene expression in diseases like cancer, studying gene regulation, and detecting RNA mutations. 3. Western Blotting (Protein) Purpose: Detects specific proteins. Method: Proteins are separated by gel electrophoresis, transferred to a membrane, and detected using antibodies specific to the target protein. Use: Diagnosing diseases with protein markers (e.g., HIV detection, autoimmune disorders, and cancer diagnosis). 4. Eastern Blotting (Post-translational Modifications) Purpose: Detects post-translational modifications of proteins, such as glycosylation. Method: Similar to Western blotting, but focuses on detecting modified proteins using specific probes or antibodies. Use: Studying protein modifications in diseases like cancer, diabetes, and neurodegenerative conditions. Implications in Diagnosis -Genetic Disorders: Southern and Northern blotting help detect mutations or abnormal gene expression patterns associated with genetic diseases (e.g., sickle cell anemia, cystic fibrosis). -Cancer: Western blotting detects cancer-associated proteins (e.g., p53 mutation detection). -Infectious Diseases: Western blotting is used for detecting HIV antibodies, confirming other viral infections, or identifying bacterial proteins in diagnostic tests. -Autoimmune Diseases: Western blotting helps detect autoantibodies, used in diagnosing conditions like lupus or rheumatoid arthritis. Conclusion Blotting techniques are powerful tools in molecular diagnostics, enabling the detection of genetic mutations, disease markers, and protein expression. They have wide applications in research and clinical diagnostics for a variety of genetic, infectious, and autoimmune diseases.

Answer 7

1. Chromosomal Abnormalities: -Down Syndrome (Trisomy 21): Screened through non-invasive prenatal testing (NIPT), maternal serum screening, and ultrasound. -Trisomy 18 (Edwards Syndrome) - Trisomy 13 (Patau Syndrome): Also detected through NIPT, combined first-trimester screening, and second-trimester screening (e.g., quadruple screen). 2. Neural Tube Defects: o Spina Bifida and Anencephaly: Detected through maternal serum screening (elevated alpha-fetoprotein levels) and ultrasound. 3. Cystic Fibrosis: -Carrier screening for CFTR mutations is offered to high-risk populations (family history, ethnicity). Newborn Screening 1. Metabolic Disorders: -Phenylketonuria (PKU): A condition where the body cannot metabolize phenylalanine, leading to intellectual disability. -Congenital Hypothyroidism: Causes developmental delays and growth problems if untreated. -Galactosemia: A disorder affecting the metabolism of galactose, leading to liver damage, cataracts, and intellectual disability. -Maple Syrup Urine Disease: A disorder where the body cannot process certain amino acids, leading to brain damage. 2. Hemoglobinopathies: -Sickle Cell Disease and Thalassemia: Identified through blood tests for abnormal hemoglobin or carrier status. 3. Cystic Fibrosis: -CFTR mutations are screened to detect cystic fibrosis, which affects the lungs and digestive system. 4. Inborn Errors of Metabolism: -Disorders like Medium-chain acyl-CoA dehydrogenase deficiency (MCAD) and Organic acidemia that disrupt energy metabolism. 5. Congenital Adrenal Hyperplasia (CAH): -A genetic disorder affecting hormone production, leading to salt imbalances and sexual development issues.

Answer 8

Polymerase Chain Reaction (PCR) is a molecular technique used to amplify a specific segment of DNA, creating millions of copies from a small initial sample. PCR is based on the repetitive cycling of DNA denaturation, annealing, and extension, which allows the targeted DNA region to be exponentially replicated. Steps of PCR 1. Denaturation: The DNA sample is heated to around 94–98°C, causing the double-stranded DNA to separate into two single strands. 2. Annealing: The temperature is lowered to 50–65°C, allowing short DNA primers to bind to the complementary sequences on the single-stranded DNA. 3. Extension: The temperature is raised to 75–80°C, where a DNA polymerase enzyme extends the primers, synthesizing new DNA strands. 4. Amplification: These steps are repeated for 20-40 cycles, resulting in millions of copies of the target DNA segment. Uses in Genetic Analysis 1. Mutation Detection: PCR amplifies specific DNA regions for analysis, helping detect mutations in genes (e.g., for cystic fibrosis or sickle cell anemia). 2. Genetic Profiling: PCR is used in DNA fingerprinting for forensic analysis, paternity testing, and ancestry studies. 3. Gene Expression: PCR (often quantitative, qPCR) is used to measure mRNA levels, helping assess gene expression in different conditions, such as in cancer research or infectious disease detection. 4. Pathogen Detection: PCR is used to detect pathogens like viruses and bacteria by amplifying their genetic material (e.g., HIV, COVID-19, TB). 5. Cloning and Gene Therapy: PCR amplifies genes of interest for cloning into vectors or for therapeutic purposes, such as gene editing and gene therapy.

Week 3 General principles Flashcards

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