Ch 3Hereditary Influences on Health Promotion of the Child and Family Flashcards
Genetic Influences on Health
> Human Genome Project
> Pharmacogenetics/Pharmacogenomics
- Allows individualized medication selection and dosing to improve efficacy and safety
> Heredity-environmental interplay in diseases
- Genetic predisposition activated by an environmental trigger
–Multifactorial diseases
Examples of Heredity and Environment Interplay in Human Diseases
> Single-gene disorders
-PKU
> Cancer
> Anomalies from prenatal environmental causes
- Congenital amputation caused by amniotic bands
- Cleft lip and palate
Congenital Anomalies
Deformations
Disruptions
Dysplasias
Malformations
Syndrome
Association
Sequence
Chromosomes
A normal somatic cell has 23 pairs of chromosomes (46 total)
*Suffix “Somy”
Gain or loss of a chromosome
One missing = Monosomy—often result in spontaneous AB—incompatible w/ life
Extra one = Trisomy
Chromosome Disorders
> Definition
- Deviation in structure or number of a chromosome
> Result from
- Duplication of genetic material or
- Loss of genetic material
–“Monogenetic” or “polygenetic” disorders
Chromosome Disorders—Types
Structural abnormality:
> Loss, addition, rearrangement, or exchange of genes of a chromosome
> Usually results from an error in cell division in sperm or ovum (parents are normal
Numeric Chromosome Abnormalities
> Occur whenever entire chromosomes are added or deleted
> Euploidy: Uniform addition of chromosomes to all the original pairs
> Trisomy: Additional chromosome
> Monosomy: Deletion of one chromosome
- Most types are incompatible with life
Autosomal Inheritance Patterns
> Numeric alterations affecting the autosomes
> Examples include some of the most common trisomies:
Trisomy 21 (Down syndrome)
Trisomy 18 (Edwards syndrome)
Trisomy 13 (Patau syndrome)
Syndrome
A recognized pattern of malformations with a single, specific anatomic, physiologic, or biochemical cause
Trisomy 21 = Down Syndrome
> Trisomy—92% of all cases
- Female with a trisomy is 47, XX,+21
- Male with trisomy is 47, XY,+21
- The extra chromosome 21 is unattached and segregates freely during meiosis
- The risk for this type increases with maternal age
> Translocation Down syndrome—4% of all cases
- Male Robertsonian translocation between acrocentric chromosomes 14 and 21 is 46, XY,t(14;21).
- The majority of cases are without family history
- Approximately 25% have one balanced translocation carrier parent
> Mosaic Down syndrome—Rare cases
- The female with mosaic Down syndrome is 46, XX/47, XX,+21.
- Results from mitotic nondisjunction during early embryonic development of a normal zygote. Affected children have mixed cell populations, some with the normal karyotype, others with the extra chromosome.
-The proportion of trisomic cells affects the child’s developmental potential and syndrome-associated potential health problems.
Trisomy 18
AKA. Edwards syndrome
-Severe cognitive impairment and physical abnormalities
-Short life span
Trisomy 13
AKA Patau syndrome
-Severe malformations = greater gene imbalance
-Short life span
Mosaicism
> The presence of two or more chromosomally distinct cell lines in the same individual
> Extent (expressed as a percentage) depends on the stage of embryonic development during which the cell division error occurs
Aneuploidy
An abnormal chromosome pattern in which the total number of chromosomes is not a multiple of the haploid number (23)
The most common aneuploidies in humans are trisomies
Sex Chromosome Aneuploidies
> Alteration in the number of sex chromosomes
> Profound effects are rare
> May have decreased intelligence or learning disabilities
Examples:
Klinefelter syndrome
Turner syndrome
*Klinefelter syndrome occurs when a male has an extra X chromosome.
*Turner syndrome is a genetic disorder in which a female has a single X chromosome compared to the two sex chromosomes in most people.
