Genetics and Molecular Biology

Genetics Study Notes

Human Genome Project

• A collaborative research project to map the entire human genome, identifying all genes and their sequences
• Significance: understanding the genetic basis of human health and disease, enabling diagnosis, treatment, and prevention

DNA, Genes, Chromosomes, and RNA

• DNA (Deoxyribonucleic acid): carries genetic information, providing instructions for development and function
• Genes: basic units of heredity, carrying information from one generation to the next
• Chromosomes: thread-like structures containing DNA, typically 23 pairs in humans
• RNA (Ribonucleic acid): plays a crucial role in protein synthesis, carrying genetic information from DNA

Recombinant DNA Technology

• A laboratory technique that combines genetic material from different sources, creating new DNA sequences
• Allows for genetic engineering, gene cloning, and gene expression

Congenital vs. Genetic Disorders

• Congenital: present at birth, may be genetic or environmental in origin
• Genetic: directly caused by genetic mutations or variations

Punnett Square

• A graphical tool for predicting genotypes and phenotypes of offspring, based on parental genotypes

Penetrance and Expressivity

• Penetrance: the proportion of individuals expressing a particular genotype
• Expressivity: the degree to which a genotype is expressed, varying from person to person

X-Linked Inheritance Patterns

• Traits determined by genes on the X chromosome
• Males, with only one X chromosome, are more likely to express X-linked recessive traits

Marfan Syndrome

• Autosomal dominant genotype
• Pathophysiology: defective fibrillin-1 protein, affecting connective tissue
• Symptoms: skeletal, ocular, and cardiovascular abnormalities
• Prognosis: variable, with early diagnosis and management improving outcomes

Huntington Disease

• Autosomal dominant genotype
• Pathophysiology: expanded CAG repeat in the Huntingtin gene, leading to neurodegeneration
• Symptoms: progressive cognitive decline, chorea, and psychiatric disturbances
• Prognosis: degenerative, with no cure

PKU (Phenylketonuria)

• Autosomal recessive genotype
• Pathophysiology: deficiency of phenylalanine hydroxylase, leading to toxic phenylalanine accumulation
• Symptoms: intellectual disability, seizures, and behavioral abnormalities
• Prognosis: dietary restriction of phenylalanine can prevent symptoms

Tay-Sachs Disease

• Autosomal recessive genotype
• Pathophysiology: deficiency of hexosaminidase A, leading to GM2 ganglioside accumulation
• Symptoms: progressive neurological degeneration, seizures, and vision loss
• Prognosis: fatal, usually in early childhood
• At-risk population: Ashkenazi Jewish descent, Cajun, and French Canadian ancestry

Fragile X Syndrome

• Pathophysiology: expansion of CGG repeats in the FMR1 gene, leading to intellectual disability
• Symptoms: intellectual disability, physical and behavioral abnormalities
• Prognosis: variable, with early diagnosis and intervention improving outcomes

Multifactorial Inheritance

• Results from the interaction of multiple genetic and environmental factors
• Examples: heart disease, diabetes, and certain types of cancer

Chromosomal Disorders

• Result from abnormalities in chromosome number or structure
• Examples: Trisomy 21 (Down syndrome), Monosomy X (Turner syndrome), and Polysomy X (Klinefelter syndrome)

Trisomy 21 (Down Syndrome)

• Risk factors: advanced maternal age, recurrence in families
• Features: intellectual disability, characteristic facial features, and delayed development

Monosomy X (Turner Syndrome)

• Features: short stature, ovarian dysgenesis, and congenital heart defects

Polysomy X (Klinefelter Syndrome)

• Features: tall stature, hypogonadism, and developmental delays

Prenatal Diagnostic Tools

• Available tools: ultrasound, chorionic villus sampling, amniocentesis, and non-invasive prenatal testing
• Indications: advanced maternal age, family history, and anomalous ultrasound findings

Genetics Study Notes

Human Genome Project

• A collaborative research project to map the entire human genome, identifying all genes and their sequences
• Significance: understanding the genetic basis of human health and disease, enabling diagnosis, treatment, and prevention

DNA, Genes, Chromosomes, and RNA

• DNA (Deoxyribonucleic acid): carries genetic information, providing instructions for development and function
• Genes: basic units of heredity, carrying information from one generation to the next
• Chromosomes: thread-like structures containing DNA, typically 23 pairs in humans
• RNA (Ribonucleic acid): plays a crucial role in protein synthesis, carrying genetic information from DNA

Recombinant DNA Technology

• A laboratory technique that combines genetic material from different sources, creating new DNA sequences
• Allows for genetic engineering, gene cloning, and gene expression

Congenital vs. Genetic Disorders

• Congenital: present at birth, may be genetic or environmental in origin
• Genetic: directly caused by genetic mutations or variations

Punnett Square

• A graphical tool for predicting genotypes and phenotypes of offspring, based on parental genotypes

Penetrance and Expressivity

• Penetrance: the proportion of individuals expressing a particular genotype
• Expressivity: the degree to which a genotype is expressed, varying from person to person

X-Linked Inheritance Patterns

• Traits determined by genes on the X chromosome
• Males, with only one X chromosome, are more likely to express X-linked recessive traits

Marfan Syndrome

• Autosomal dominant genotype
• Pathophysiology: defective fibrillin-1 protein, affecting connective tissue
• Symptoms: skeletal, ocular, and cardiovascular abnormalities
• Prognosis: variable, with early diagnosis and management improving outcomes

Huntington Disease

• Autosomal dominant genotype
• Pathophysiology: expanded CAG repeat in the Huntingtin gene, leading to neurodegeneration
• Symptoms: progressive cognitive decline, chorea, and psychiatric disturbances
• Prognosis: degenerative, with no cure

PKU (Phenylketonuria)

• Autosomal recessive genotype
• Pathophysiology: deficiency of phenylalanine hydroxylase, leading to toxic phenylalanine accumulation
• Symptoms: intellectual disability, seizures, and behavioral abnormalities
• Prognosis: dietary restriction of phenylalanine can prevent symptoms

Tay-Sachs Disease

• Autosomal recessive genotype
• Pathophysiology: deficiency of hexosaminidase A, leading to GM2 ganglioside accumulation
• Symptoms: progressive neurological degeneration, seizures, and vision loss
• Prognosis: fatal, usually in early childhood
• At-risk population: Ashkenazi Jewish descent, Cajun, and French Canadian ancestry

Fragile X Syndrome

• Pathophysiology: expansion of CGG repeats in the FMR1 gene, leading to intellectual disability
• Symptoms: intellectual disability, physical and behavioral abnormalities
• Prognosis: variable, with early diagnosis and intervention improving outcomes

Multifactorial Inheritance

• Results from the interaction of multiple genetic and environmental factors
• Examples: heart disease, diabetes, and certain types of cancer

Chromosomal Disorders

• Result from abnormalities in chromosome number or structure
• Examples: Trisomy 21 (Down syndrome), Monosomy X (Turner syndrome), and Polysomy X (Klinefelter syndrome)

Trisomy 21 (Down Syndrome)

• Risk factors: advanced maternal age, recurrence in families
• Features: intellectual disability, characteristic facial features, and delayed development

Monosomy X (Turner Syndrome)

• Features: short stature, ovarian dysgenesis, and congenital heart defects

Polysomy X (Klinefelter Syndrome)

• Features: tall stature, hypogonadism, and developmental delays

Prenatal Diagnostic Tools

• Available tools: ultrasound, chorionic villus sampling, amniocentesis, and non-invasive prenatal testing
• Indications: advanced maternal age, family history, and anomalous ultrasound findings