Inheritance Patterns and Genetic Disorders Flashcards

Flashcards covering Mendelian inheritance, chromosomal abnormalities, specific genetic syndromes like Down and Turner syndromes, and clinical patterns like sequences and associations.

Autosomes

The non-sex chromosomes in a human cell, excluding the $X$ and $Y$ chromosomes.

Mendelian Inheritance

A simple inheritance pattern where a disease is caused by a single abnormal gene on one of the autosomes.

Autosomal Dominant

A condition where expression of the phenotype requires only a single abnormal copy of the gene.

Autosomal Recessive

A condition where both copies of the gene must be abnormal for the phenotype to be expressed; cystic fibrosis is a key example.

Carrier

An individual who has one abnormal copy of a recessive gene but does not exhibit the disease phenotype, though they can pass the gene to offspring.

Deletion Disorder

A chromosomal disorder where a portion of a chromosome is missing, such as Cri du chat involving chromosome $5$.

Duplication Disorder

A condition where a chromosome contains twice the number of copies of a specific gene portion, such as in Charcot-Marie-Tooth on chromosome $17$.

Balanced Translocation

A reciprocal translocation where a portion of one chromosome is swapped with a portion of another without gain or loss of genetic material.

Robertsonian Translocation

A specific translocation involving acrocentric chromosomes ($13$, $14$, $15$, $21$, and $22$) where the short arms are lost and the long arms fuse at the centromere.

Trisomy

A chromosomal abnormality where an individual has three copies of a particular chromosome, resulting in a total of $47$ chromosomes.

Mosaicism

A condition where a chromosomal abnormality occurs after conception, resulting in different genetic material in different cells of the body.

Maternal Inheritance

The pattern of mitochondrial DNA transmission where all mitochondria in a zygote are derived from the mother's egg.

Karyotyping

A genetic testing method used to look at the number, size, and basic structure of an individual's chromosomes.

Microarray Testing

A method of cutting genetic material with enzymes and separating molecules by weight to identify which genes an individual expresses.

Sequence

A pattern where one initial abnormality causes a chain reaction of subsequent defects, such as the Pierre Robin sequence.

Malformation

A defect where a structure forms incorrectly from the very beginning of development.

Deformation

A defect where a normally developing body part is shaped abnormally by mechanical force, such as club foot due to limited uterine space.

Disruption

A defect where normal tissue starts forming correctly but is later damaged or interrupted, such as by amniotic bands.

Association

A cluster of defects that occur together more often than by chance, but lack a single known underlying cause, such as VACTERL.

Syndrome

A pattern of multiple anomalies linked by a specific known or suspected underlying mechanism, such as Down syndrome.

Down Syndrome (Trisomy $21$)

A genetic disorder caused by an extra copy of chromosome $21$, featuring hypotonia, brachycephaly, and upward-sloping palpebral fissures.

Brachycephaly

A clinical feature defined by a shortened front-to-back skull length and a flat occiput.

Clinodactyly

An incurved fifth finger resulting from hypoplasia of the middle phalanx.

AVSD (Atrioventricular Septal Defect)

The most common cardiac lesion in children with Down syndrome, involving defects in the atrial and ventricular septa.

Turner Syndrome (45XO)

A condition in females with a single $X$ chromosome, characterized by short stature, webbed neck, and widely spaced nipples.

Cubitus Valgus

An elbow deformity seen in Turner syndrome where the forearm is angled away from the body at more than a $15$-degree carrying angle.

Noonan Syndrome

An autosomal dominant condition featuring short stature, hypertelorism, and pulmonary valve stenosis.

DiGeorge Syndrome ($22q11$ Deletion)

A syndrome resulting from developmental defects of the $3^{rd}$ and $4^{th}$ branchial arches, featuring hypocalcaemia and thymus hypoplasia.

Klinefelter Syndrome (47XXY)

A condition in males with an extra $X$ chromosome, leading to gynaecomastia, small testicles, and infertility.

Marfan Syndrome

An autosomal dominant disorder affecting the fibrillin gene, characterized by tall stature, arachnodactyly, and risk of aortic aneurysms.

Arachnodactyly

A clinical sign of Marfan syndrome characterized by abnormally long and slender fingers.

Fragile X Syndrome

An $X$-linked condition caused by a mutation in the $FMR1$ gene, presenting with intellectual disability and macro-orchidism (large testicles).

Prader-Willi Syndrome

A condition caused by loss of functional genes on paternal chromosome $15$, resulting in neonatal hypotonia and childhood hyperphagia.

Edward Syndrome (Trisomy $18$)

A trisomy condition featuring micrognathia, overlapping fingers, and rocker-bottom feet.

Patau Syndrome (Trisomy $13$)

A trisomy condition featuring holoprosencephaly, cleft lip and palate, and postaxial polydactyly.

Angelman Syndrome

A genetic condition caused by loss of the maternal $UBE3A$ gene, featuring a happy demeanour and hand flapping.

Beckwith-Wiedemann Syndrome

A condition involving abnormal regulation of genes on chromosome $11$, featuring macrosomia and umbilical hernia.

Williams Syndrome

A deletion on chromosome $7$ resulting in a very sociable personality, starburst eyes, and supravalvular aortic stenosis.

Potter Sequence

A cascade starting with renal agenesis that leads to oligohydramnios and pulmonary hypoplasia.

VACTERL Association

A non-random cluster of anomalies including Vertebral defects, Anorectal anomalies, Cardiac defects, TE fistula, Renal abnormalities, and Limb abnormalities.