11 Questions
What is the term for a uniform addition of a chromosome to all original pairs?
Euploidy
What is the characteristic feature of Trisomy 21?
Large tongue, slanting eyes, semi-crease on hands, hypotonia, cardiac delays, and cognitive impairment
What is the name of the syndrome caused by an extra chromosome 18?
Edwards syndrome
What is the characteristic feature of X-linked recessive inheritance?
Affected individuals are principally males with symptoms
What is the name of the syndrome caused by an extra X chromosome in males?
Klinefelter syndrome
What is the characteristic feature of X-linked dominant inheritance?
A variant in one copy can cause the disorder in males
What is a characteristic of X-linked traits?
They cannot be passed from fathers to sons.
In an autosomal dominant disorder, what is the minimum number of altered gene copies required for a person to be affected?
One copy in each cell.
What is the chance of a child inheriting a mutant allele and being affected if one of their parents has an autosomal dominant disorder?
50%
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?
25%
When should the nurse collect the newborn's blood screening for genetic disorders?
After the first feeding is complete and the infant is 24 hours old.
Study Notes
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.
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