Cytogenetics & Teratology Study Guide

Flashcards covering chromosome structure, classification, abnormalities, key genetic syndromes, cytogenetic techniques, teratology principles, major teratogens, and the link between DNA repair errors and cancer.

How is a metacentric chromosome described?

The centromere is in the middle, resulting in equal arms.

What characterizes a submetacentric chromosome?

Its arms are unequal, with the centromere off-center.

Describe an acrocentric chromosome.

The centromere is near one end, leading to a long arm and a short stalk/satellite.

Which banding method is considered the gold standard for detecting deletions and duplications?

G-banding.

What does C-banding highlight?

Heterochromatin near the centromere.

What does R-banding typically highlight?

The ends of chromosomes (reversed banding pattern).

Which banding method detects microdeletions?

High-resolution banding.

What is the term for a normal multiple of 23 chromosomes?

Euploid.

What is aneuploidy, and what causes it?

Aneuploidy refers to conditions like monosomy or trisomy, often caused by nondisjunction.

What is the difference between mosaicism and chimerism?

Mosaicism involves 2+ cell lines from one zygote, while chimerism involves the fusion of 2 zygotes.

What is a Robertsonian translocation?

A type of translocation involving acrocentric chromosomes (13, 14, 15, 21, 22), where two long arms fuse and the short arms are lost.

Name a syndrome caused by a deletion on chromosome 5p.

Cri du Chat syndrome.

What is an isochromosome?

A chromosome with two identical arms, typically a mirror image, such as i(Xq).

What are the common clinical features of Down syndrome (Trisomy 21)?

Flat facies, single palmar crease, congenital heart defects (CHD), increased risk of ALL/AML, and early-onset Alzheimer's.

What are characteristic features of Edwards syndrome (Trisomy 18)?

Micrognathia, prominent occiput, clenched fists with overlapping fingers, and rocker-bottom feet, often leading to death before one year.

Which syndrome presents with cleft lip/palate, polydactyly, and holoprosencephaly?

Patau syndrome (Trisomy 13).

What are the key clinical features of Turner syndrome (45,X)?

Short stature, webbed neck, streak ovaries, bicuspid aortic valve, and coarctation of the aorta.

Describe the typical presentation of Klinefelter syndrome (47,XXY).

Tall male stature, small testes, gynecomastia, and infertility.

What causes a 46,XX male, and what are its features?

SRY translocation, leading to azoospermia and small testes.

How is 46,XY Female (Swyer syndrome) characterized?

Streak gonads, absence of puberty, infertility, and increased risk of osteoporosis.

Which syndrome is associated with maternal 15q11-13 loss, seizures, 'happy puppet' demeanor, and severe intellectual disability?

Angelman syndrome.

What syndrome results from paternal 15q11-13 loss, leading to hyperphagia, obesity, and almond-shaped eyes?

Prader-Willi syndrome.

What are the features of Williams syndrome?

7q11 deletion, 'elfin' facial features, outgoing personality, and supravalvular aortic stenosis.

Which syndrome is linked to a 22q11.2 deletion, causing conotruncal heart defects, thymic hypoplasia, hypocalcemia, and cleft palate?

DiGeorge syndrome.

What does the acronym WAGR stand for in relation to a syndrome caused by an 11p13 deletion?

Wilms tumor, Aniridia, Genitourinary defects, and developmental delay.

Which cytogenetic technique uses fluorescent probes to detect microdeletions or duplications?

FISH (Fluorescence In Situ Hybridization).

What is the primary use of CGH (Comparative Genomic Hybridization)?

Detecting genome-wide copy number variations.

What is the critical period for teratogen exposure, and why is it significant?

Weeks 3-8 (organogenesis), as this is when the fetus is most vulnerable to teratogenic effects.

What are some characteristic features of Fetal Alcohol Syndrome (FAS)?

Smooth philtrum, thin vermilion border of the upper lip, small palpebral fissures, and intellectual disability.

Which teratogen is known to cause severe limb defects?

Thalidomide.

What are some common effects of maternal diabetes on fetal development?

Caudal regression, macrosomia, and congenital heart defects (CHD).

Which teratogenic infection group can cause growth restriction, microcephaly, and cataracts?

TORCH infections (Toxoplasmosis, Other, Rubella, Cytomegalovirus, Herpes/HIV).

What is a key preventative measure against neural tube defects (NTDs)?

Folate supplementation.

Errors in which DNA repair pathway can lead to translocations and deletions?

NHEJ (Non-Homologous End Joining) repair.

Which specific somatic translocation is associated with Chronic Myeloid Leukemia (CML)?

t(9;22), resulting in the BCR-ABL fusion gene (Philadelphia chromosome).