Chapter 21 – Congenital and Genetic Disorders

This set of vocabulary flashcards covers key genetic, chromosomal, and developmental concepts, specific inherited disorders, mechanisms of inheritance, diagnostic tools, and modern genetic technologies presented in Chapter 21 on Congenital and Genetic Disorders.

Chromosome

Thread-like structure of DNA and protein carrying genetic information; humans normally have 23 pairs.

Autosomes

The 22 pairs of chromosomes that are not sex chromosomes.

Sex Chromosomes

The X and Y chromosomes that determine biological sex (XX = female, XY = male).

Karyotype

Visual arrangement of chromosomes by size and shape used to diagnose chromosomal disorders.

Genotype

An individual’s actual genetic makeup present in every somatic cell.

Phenotype

Observable characteristics that result from gene expression.

Congenital Disorder

Abnormality present at birth caused by inherited genes or developmental factors.

Single-Gene Disorder

Disease produced by mutation in one gene; inheritance can be recessive, dominant, or X-linked.

Autosomal Recessive Disorder

Condition expressed only in homozygotes; both parents must pass the mutant allele (e.g., cystic fibrosis).

Autosomal Dominant Disorder

Condition expressed when only one mutant allele is present; no true carrier state (e.g., Marfan syndrome).

X-Linked Recessive Disorder

Mutation on X chromosome expressed in hemizygous males; females are usually carriers (e.g., hemophilia A).

X-Linked Dominant Disorder

Mutation on X chromosome expressed in heterozygous males and females with reduced penetrance in females (e.g., Fragile X).

Carrier

Heterozygous individual who harbors a recessive disease allele but shows no clinical signs.

Polygenic Inheritance

Trait controlled by several genes often interacting with environment.

Multifactorial Disorder

Disease resulting from both genetic predisposition and environmental triggers (e.g., cleft palate).

Chromosomal Anomaly

Numerical or structural abnormality in chromosomes, often from meiotic error.

Nondisjunction

Failure of homologous chromosomes to separate, producing gametes with abnormal chromosome number.

Translocation

Rearrangement in which part of one chromosome attaches to another chromosome.

Trisomy 21 (Down Syndrome)

Chromosomal disorder with extra chromosome 21 causing characteristic physical and cognitive deficits.

Monosomy X (Turner Syndrome)

45,XO karyotype producing short stature, streak ovaries, and infertility in females.

Polysomy X (Klinefelter Syndrome)

47,XXY karyotype producing tall males with small testes and infertility.

Cystic Fibrosis

Autosomal recessive disease causing defective chloride channels and viscous secretions in lungs and pancreas.

Phenylketonuria (PKU)

Autosomal recessive defect in phenylalanine hydroxylase leading to toxic phenylalanine levels; controlled by diet.

Tay-Sachs Disease

Autosomal recessive deficiency of hexosaminidase A causing neurodegeneration in infancy.

Sickle Cell Anemia

Autosomal recessive hemoglobin S mutation resulting in sickled red blood cells and vaso-occlusive crises.

Marfan Syndrome

Autosomal dominant connective-tissue disorder due to fibrillin-1 mutation; tall stature, aortic dilation.

Huntington Chorea

Autosomal dominant neurodegenerative disease with late-onset choreiform movements and dementia.

Adult Polycystic Kidney Disease

Autosomal dominant disorder characterized by bilateral renal cysts leading to renal failure.

Familial Hypercholesterolemia

Autosomal dominant LDL-receptor defect causing markedly elevated cholesterol levels.

Fragile X Syndrome

X-linked dominant mutation in FMR1 gene; leading inherited cause of intellectual disability.

Duchenne Muscular Dystrophy

X-linked recessive absence of dystrophin causing progressive muscle weakness in boys.

Hemophilia A

X-linked recessive deficiency of clotting factor VIII leading to bleeding tendency.

Teratogen

Agent that produces fetal malformation when exposure occurs during pregnancy.

TORCH Infections

Group of maternal infections (Toxoplasma, Others, Rubella, Cytomegalovirus, Herpes) causing congenital anomalies.

Organogenesis

Critical first 8 weeks of embryonic development when major organs form and teratogens have greatest effect.

Diagnostic Prenatal Testing

Techniques such as amniocentesis or chorionic villus sampling used to detect fetal abnormalities.

Alpha-Fetoprotein Test

Maternal serum screening for neural-tube defects and some chromosomal anomalies.

Gene Therapy

Experimental technique introducing normal genes to correct genetic disorders at their source.

Genetic Engineering

Manipulation and transfer of genes among organisms for medical or agricultural purposes.

Genetic Screening

Testing populations to identify individuals carrying specific disease alleles.

Proteomics

Study of protein expression profiles to design ‘designer drugs’ tailored to genotype.

Designer Drug

Medication engineered to interact optimally with proteins encoded by a patient’s specific genes.

Delayed Lethal Genotype

Autosomal dominant mutation that manifests clinically later in life, often after reproduction (e.g., Huntington’s).

Hypotonia

Reduced muscle tone; common physical finding in infants with Down syndrome.

Single Palmar Crease

Transverse crease across palm often associated with Down syndrome.