Cytogenetics: Chromosome Disorders and Syndromes

What is the term for a uniform addition of a chromosome to all original pairs?

What is the characteristic feature of Trisomy 21?

What is the name of the syndrome caused by an extra chromosome 18?

What is the characteristic feature of X-linked recessive inheritance?

What is the name of the syndrome caused by an extra X chromosome in males?

What is the characteristic feature of X-linked dominant inheritance?

What is a characteristic of X-linked traits?

In an autosomal dominant disorder, what is the minimum number of altered gene copies required for a person to be affected?

What is the chance of a child inheriting a mutant allele and being affected if one of their parents has an autosomal dominant disorder?

What is the chance of a child having a condition if both parents are carriers of an autosomal recessive variant but do not have the condition?

When should the nurse collect the newborn's blood screening for genetic disorders?

Chromosome Disorders (Cytogenetics)

Euploidy: uniform addition of chromosomes to all original pairs
Types of euploidy: trisomy and monosomy

Trisomy

Trisomy: additional chromosome added to a pair
Trisomy 21 (Down syndrome): Chr-47, XX, +21
- Symptoms: large tongue, slanting eyes, semi-crease on hands, hypotonia, cardiac delays, cognitive impairment
Trisomy 18 (Edwards syndrome): Chr-47, XX, +18
- Symptoms: severe cognitive impairment and physical abnormalities, shorter life span
Trisomy 13 (Patau syndrome): Chr-47, XX, +13
- Symptoms: severe malformations, short life span

Sex Chromosome Aneuploidies

Alterations in the number of sex chromosomes
Examples: Klinefelter syndrome, Turner syndrome
Klinefelter syndrome (47-XXY): gynecomastia, small testes, infertility, long arms/legs
Turner syndrome (45-X or 45-X0): lymphedema at birth, short stature, lack of secondary sex characteristics during adolescence, cardiac issues

Inheritance Patterns

X-linked Recessive inheritance
- Affected individuals are principally males
- Carrier females are normal, males are not carriers
- Example: Hemophilia
X-linked Dominant inheritance
- Variant in one copy can cause the disorder in males (with one X)
- Variant can cause the disorder in females (with two X's)
- Fathers cannot pass X-linked traits to their sons
- Example: Fragile X Syndrome
Autosomal Dominant inheritance
- One altered gene copy in each cell is sufficient for the disorder
- Children of an affected parent have a 50% chance of inheriting the mutant allele and being affected
- Examples: Huntington's disease, Marfan syndrome
Autosomal Recessive inheritance
- Variants occur in both copies of the gene in each cell
- If both parents are carriers, their kids have a 25% chance of having the condition
- Examples: Cystic fibrosis, Sickle cell disease

This quiz covers chromosome disorders, including Euploidy, Trisomy, and various syndromes such as Trisomy 21, Trisomy 18, and Trisomy 13. Identify symptoms, characteristics, and life expectancy of these conditions.