Preconception, Genetics, and Chromosomal Disorders

A set of vocabulary flashcards covering preconception genetics, trait inheritance, autosomal recessive/dominant disorders, trisomies, and sex-linked disorders.

Gamete

A mature male or female germ cell (ova or sperm) containing 23 single chromosomes.

Zygote

A single cell created at fertilization by an ovum and sperm, forming 23 pairs of chromosomes.

Chromosomes

Strings of genetic material in the nuclei of cells that determine an individual's genetic makeup, organized into 23 pairs.

DNA

The material that makes up chromosomes and genes.

Genes

Pieces of genetic material that control or influence traits.

Autosomes

The 22 pairs of chromosomes that contain most of an individual's genetic information and are not sex chromosomes.

Sex Chromosomes

The 23rd pair of chromosomes ($\text{X}$ and $\text{Y}$) that determine an individual's biological sex.

Androgens

Steroid hormones released from the $\text{Y}$ chromosome between 4–8 weeks that assist in gonad and brain development.

Ambiguous Genitalia

A physical condition resulting from maternal exposure to androgens during pregnancy.

Identical Twins (Monozygotic)

Twins occurring in $1 \text{ in } 250$ births, formed when a single egg fertilized by one sperm splits in halves to develop with identical genetic composition.

Fraternal Twins (Dizygotic)

The more common type of twins, formed when two separate eggs are fertilized by two separate sperm, resulting in different genetic compositions.

Genotype

The unique genetic blueprint of an individual that provides instructions for growth and development.

Phenotype

An individual's particular set of observed, visible characteristics.

Autosomal Dominant

A pattern of inheritance in which a single dominant gene on an autosome influences a person's phenotype.

Autosomal Recessive

A pattern of inheritance in which two recessive genes are necessary to produce an associated trait.

Homozygous

Carrying two of the same genes for a trait—either two dominant or two recessive genes.

Heterozygous

Carrying one dominant gene and one recessive gene for a specific trait.

Polygenic Inheritance

An inheritance pattern where many genes influence the phenotype by blending dominant and recessive qualities (such as skin color or eye color).

Genomic Imprinting

A chemical marker on a gene that identifies it as coming from either the mother or father, turning on or off normal developmental processes.

Phenylketonuria (PKU)

An autosomal recessive genetic metabolic disorder caused by a deficiency of the PAH (phenylalanine hydroxylase) enzyme, leading to phenylalanine toxin buildup in the brain.

Sickle-Cell Disease

An autosomal recessive disorder where stress causes red blood cells to sickle, causing artery/vein blockages known as a sickle-cell crisis.

Tay-Sachs Disease

An autosomal recessive disorder that destroys nerve cells in the brain and spinal cord, leading to progressive loss of movement, responsiveness, and seizures.

Cystic Fibrosis

An autosomal recessive disorder affecting mucus-, sweat-, and digestive enzyme-producing cells, causing thick mucus to block lung alveoli and pancreatic ducts.

Huntington's Disease

An autosomal dominant disorder causing progressive breakdown of brain nerve cells, affecting psychological and motor functioning in adulthood.

Trisomy

A genetic condition characterized by having 3 copies of a specific autosome.

Trisomy 13 (Patau Syndrome)

A severe autosomal trisomy disorder characterized by cleft lip/palate, extra digits, spinal cord abnormalities, small head/eyes, heart defects, and kidney cysts.

Trisomy 18 (Edward's Syndrome)

A severe autosomal trisomy disorder characterized by overlapping fingers, heart/lung abnormalities, clubfeet, small physical size, decreased muscle tone, and low-set ears.

Trisomy 21 (Down Syndrome)

The most common trisomy, caused by 3 copies of chromosome 21, presenting with low-set ears, almond-shaped eyes, single palmar crease, flat nasal bridge, and epicanthic folds.

Epicanthic Fold

A fold of skin on the upper eyelid, which serves as a physical characteristic of Trisomy 21 (Down Syndrome).

Fragile X Syndrome

A sex-linked disorder caused by a damaged spot on the X chromosome, characterized by cognitive impairment, hyperactivity, delayed speech, elongated face, highly arched palate, and prominent ears.

Hemophilia

A sex-linked disorder caused by an issue on the X chromosome where blood lacks the necessary chemical components to clot.

Klinefelter Syndrome

A sex-linked disorder affecting males who have an extra X chromosome ($\text{XXY}$), resulting in underdeveloped testes, low sperm counts, language delays, and mixed secondary sex characteristics at puberty.

Turner Syndrome

A sex-linked disorder in females caused by the complete or partial absence of one X chromosome, characterized by short stature, webbed neck, sterility, streak ovaries, and potential coarctation of the aorta.

Consanguinity

The mating of close relatives, which reduces genetic diversity and increases the risk of recessive genes being expressed and causing birth defects.

Gamete

A mature male or female germ cell (ova or sperm) containing 23 single chromosomes.

Zygote

A single cell created at fertilization by an ovum and sperm, forming 23 pairs of chromosomes.

Chromosomes

Strings of genetic material in the nuclei of cells that determine an individual's genetic makeup, organized into 23 pairs.

DNA

The material that makes up chromosomes and genes.

Genes

Pieces of genetic material that control or influence traits.

Autosomes

The 22 pairs of chromosomes that contain most of an individual's genetic information and are not sex chromosomes.

Sex Chromosomes

The 23rd pair of chromosomes ($\text{X}$ and $\text{Y}$) that determine an individual's biological sex.

Androgens

Steroid hormones released from the $\text{Y}$ chromosome between 4–8 weeks that assist in gonad and brain development.

Ambiguous Genitalia

A physical condition resulting from maternal exposure to androgens during pregnancy.

Identical Twins (Monozygotic)

Twins occurring in $1 \text{ in } 250$ births, formed when a single egg fertilized by one sperm splits in halves to develop with identical genetic composition.

Fraternal Twins (Dizygotic)

The more common type of twins, formed when two separate eggs are fertilized by two separate sperm, resulting in different genetic compositions.

Genotype

The unique genetic blueprint of an individual that provides instructions for growth and development.

Phenotype

An individual's particular set of observed, visible characteristics.

Autosomal Dominant

A pattern of inheritance in which a single dominant gene on an autosome influences a person's phenotype.

Autosomal Recessive

A pattern of inheritance in which two recessive genes are necessary to produce an associated trait.

Homozygous

Carrying two of the same genes for a trait—either two dominant or two recessive genes.

Heterozygous

Carrying one dominant gene and one recessive gene for a specific trait.

Polygenic Inheritance

An inheritance pattern where many genes influence the phenotype by blending dominant and recessive qualities (such as skin color or eye color).

Genomic Imprinting

A chemical marker on a gene that identifies it as coming from either the mother or father, turning on or off normal developmental processes.

Phenylketonuria (PKU)

An autosomal recessive genetic metabolic disorder caused by a deficiency of the PAH (phenylalanine hydroxylase) enzyme, leading to phenylalanine toxin buildup in the brain.

Sickle-Cell Disease

An autosomal recessive disorder where stress causes red blood cells to sickle, causing artery/vein blockages known as a sickle-cell crisis.

Tay-Sachs Disease

An autosomal recessive disorder that destroys nerve cells in the brain and spinal cord, leading to progressive loss of movement, responsiveness, and seizures.

Cystic Fibrosis

An autosomal recessive disorder affecting mucus-, sweat-, and digestive enzyme-producing cells, causing thick mucus to block lung alveoli and pancreatic ducts.

Huntington's Disease

An autosomal dominant disorder causing progressive breakdown of brain nerve cells, affecting psychological and motor functioning in adulthood.

Trisomy

A genetic condition characterized by having 3 copies of a specific autosome.

Trisomy 13 (Patau Syndrome)

A severe autosomal trisomy disorder characterized by cleft lip/palate, extra digits, spinal cord abnormalities, small head/eyes, heart defects, and kidney cysts.

Trisomy 18 (Edward's Syndrome)

A severe autosomal trisomy disorder characterized by overlapping fingers, heart/lung abnormalities, clubfeet, small physical size, decreased muscle tone, and low-set ears.

Trisomy 21 (Down Syndrome)

The most common trisomy, caused by 3 copies of chromosome 21, presenting with low-set ears, almond-shaped eyes, single palmar crease, flat nasal bridge, and epicanthic folds.

Epicanthic Fold

A fold of skin on the upper eyelid, which serves as a physical characteristic of Trisomy 21 (Down Syndrome).

Fragile X Syndrome

A sex-linked disorder caused by a damaged spot on the X chromosome, characterized by cognitive impairment, hyperactivity, delayed speech, elongated face, highly arched palate, and prominent ears.

Hemophilia

A sex-linked disorder caused by an issue on the X chromosome where blood lacks the necessary chemical components to clot.

Klinefelter Syndrome

A sex-linked disorder affecting males who have an extra X chromosome ($\text{XXY}$), resulting in underdeveloped testes, low sperm counts, language delays, and mixed secondary sex characteristics at puberty.

Turner Syndrome

A sex-linked disorder in females caused by the complete or partial absence of one X chromosome, characterized by short stature, webbed neck, sterility, streak ovaries, and potential coarctation of the aorta.

Consanguinity

The mating of close relatives, which reduces genetic diversity and increases the risk of recessive genes being expressed and causing birth defects.

Physical manifestations of Phenylketonuria (PKU)

Toxin buildup in the brain due to PAH enzyme deficiency, leading to severe developmental delays if phenylalanine is consumed.

Physical characteristics of Sickle-Cell Disease

Deformed, sickled red blood cells triggered by stress (cold, illness) that block blood vessels, leading to a sickle-cell crisis and reduced oxygen delivery.

Physical characteristics of Tay-Sachs Disease

Progressive loss of motor skills (inability to sit, crawl, or roll over), seizures, hearing loss, and total loss of movement resulting from nerve cell destruction in the brain and spinal cord.

Physical characteristics of Cystic Fibrosis

Thick, viscous mucus blocking lung alveoli (air sacs) and pancreatic ducts, leading to severe respiratory and digestive complications.

Physical characteristics of Huntington's Disease

Involuntary muscle movements, loss of motor coordination, and difficulty swallowing caused by progressive breakdown of brain nerve cells in adulthood.

Physical characteristics of Trisomy 13 (Patau Syndrome)

Cleft lip/palate, extra fingers or toes (polydactyly), spinal cord abnormalities, small head (microcephaly), small eyes, ear malformations, heart defects, and kidney cysts.

Physical characteristics of Trisomy 18 (Edward's Syndrome)

Overlapping fingers, clubfeet, small physical size, decreased muscle tone, low-set ears, and severe heart/lung abnormalities.

Physical characteristics of Trisomy 21 (Down Syndrome)

Flat nasal bridge, epicanthic eyelid folds, almond-shaped eyes, low-set ears, single palmar crease, and low muscle tone.

Physical characteristics of Fragile X Syndrome

Elongated face, highly arched palate, large or prominent ears, broad forehead, and strabismus (cross-eyed).

Physical characteristics of Hemophilia

Inability of the blood to clot properly due to missing chemical clotting components, leading to excessive bleeding.

Physical characteristics of Klinefelter Syndrome ($\text{XXY}$)

Underdeveloped testes, low sperm count, tall stature with long limbs, narrow shoulders, wide hips, breast development (gynecomastia), reduced body hair, and female-type pubic hair pattern.

Physical characteristics of Turner Syndrome

Short stature, webbed neck, broad chest with widely spaced nipples, low posterior hairline, streak ovaries (sterility/amenorrhea), coarctation of the aorta, pigmented nevi, and peripheral lymphedema at birth.