Genetics Flashcards
Congenital
Present at birth, inherited, genetic or developmental defects due to damage in utero
Genetic
Consequences of gene changes to the 23 chromosomes in each cell
Chromosomal
Abnormal or dislocation of chromosomes
Developmental
Damage to body structures during development or shortly after birth
Multifactorial
Combo of genetic predisposition and exposure
Chromosome
DNA storage unit
- threadlike strands of DNA wrapped around protein in each cell nucleus which transmits genetic info
- human DNA organized into 2 sets of 23 (22 = autosomal, 23rd = sex)
- XX female, XY male
Genes
- instruction manual
- code for cells to make protein molecules
- two copies of each gene
- 25000 genes
Alleles
DNA sequence of a particular gene that occupies a given location on a chromosome - rungs
- “functional unit”
- dominant and recessive
- in an organism that has two copies of each chromosome, two alleges make up the individual’s genotype
Genotype
- an individual’s collection of genes, genetic make up or allele combination
- refers to the two alleles inherited from a particular gene (one from each parent)
Phenotype
- expression of the genotype contribute to the individual’s observable traits
Epigenetics
The study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself
Dominant traits
Occurs when one gene is sufficient to express a trait
- masks the presence of a recessive gene
- can be inherited from a single parent
Recessive trait
Expressed only when two copies of the gene are present
- seen only in the absence of dominant gene (or in males, if it is present on X and has no matching gene on Y)
Autosomal dominant diseases
- Huntington’s
- Osteogenesis imperfecta
- Marfan’s syndrome
Huntington’s
- progressive neurological disease
- genetic mutation on 4th chromosome
- abnormal production of huntington protein
- 50/50 chance of inheriting this gene from parent (if present, person has disease)
- symptoms start in 30-40s
- 10-20 yr lifespan after dx
- genetic testing available, but may not want
Osteogenesis imperfecta
Brittle bone disease
- genetic defect on genes responsible for collagen synthesis
- rare congenital disorder of collagen synthesis
- 25% no family Hx, spontaneous gene mutation
- wide range of presentations: short, thin skin, joint hypermobility
OI treatment/management
- fracture prevention and control
- positioning and orthosis
- careful handling, PROM without force, family education, swimming, strengthening
- prognosis: varies from relatively normal life span
Marfan’s syndrome
Disease of connective tissue, typically affecting bones and blood vessels, long limbs, and heart defects
- genetic defect affects structure of protein fibrillin
Autosomal recessive
- Both parents pass on defective gene: homozygous (2 recessive genes) child has genotype and phenotype
- one parent passes on 1 defective gene: heterozygous child who is a carrier (with genotype) but without signs (phenotype)
- spinal muscular atrophy - sickle cell anemia - cystic fibrosis
Spinal muscular atrophy
- 1/50 carries
- 2nd most fatal autosomal recessive disorder (after cystic fibrosis)
- 1/15000 live births
- chromosome #5 gene deletion
- degeneration of anterior horn cells
- progressive atrophy of skeletal muscles and respiratory insufficiency / hypoventilation
SMA management
Dx: muscle biopsy, electromyogram
- treatment: symptomatic and preventive
- pulmonary infection, orthopedic problems, feeding, scoliosis
- prognosis: varies depending upon onset, death 2-12 years later
- *therapy: positioning, head and trunk control, standing, and aquatic therapy
Cystic fibrosis
- most common genetic inherited disease in the US
- disease of pancreas that leads to altered production by mucous membranes
- defective gene and protein on chromosome #7
Sickle cell anemia
- 1/12 African-Americans carry gene for disease
- disease of RBCs: fucked shape and cant carry oxygen
Chromosomal diseases
Chromosomes either break or fail to separate during gamete formation
- results in abnormal placement of part of the chromosome, altered structure, or an abnormal number of chromosomes
- these birth defects are more common when the mother is over the age of 35
- NOT inherited (spontaneous, random change)
Trisomy
- nondisjunction occurs
- chromosome pair doesn’t separate during gamete formation
- 3 chromosomes, so 47 total
- trisomy 21 = downs
- trisomy 18 or 13 are high mortality rate within 1st year
Monosomy
Turner’s syndrome
- affects only females
- female only has one X
- failure of ovaries and other sex organs to mature (sterile)
- cardiovascular defects
- dwarfism
- webbed neck (loose folds of skin)
Single gene disorders
A disorder that is caused by 1 abnormal gene
- result of genetic mutation, change in 1 gene in reproductive cells, then mutation is passed on to future generations
- 1/200 births
- X linked, recessive and dominant disorders
- color blindness - cystic fibrosis
X linked dominant disorders
- inherited dominant allele carried on X chromosome
- males and females can be affected
- mutation of affected X chromosome appears constricted or broken
- fragile X syndrome
Fragile X syndrome
- very rare
- laundry list
- Y genes do not exist to cover or replace genes on X
- affects dudes mostly
X linked recessive traits
- a trait transmitted by a gene located on the X chromosome; also called sex-linked
- sex-linked disorders are typically carried by the X/female sex chromosome
- recessive genes, but lack matching normal gene on Y chromosome
Why do men get X-linked diseases more than women?
- X and Y chromosomes do not carry the same info
- X tends to carry more genetic info than Y chromosomes
- X linked diseases usually occur in males because males have only 1
- a single recessive gene on that X chromosome will cause the disease
Muscular dystrophies
- largest and most common group of inherited progressive neuromuscular disorder
- any time in life span
- symmetrical muscle wasting
- 6 types: Becker’s, facioscapulohumeral, limb-girdle, myotonic, muscular dystrophy congénita
- pseudo-hypertrophic (calves) connective tissue and fat deposits
Hemophilia
- bleeding disorder, lack of clotting factor, 10 proteins
- signs: excessive bruising, joint bleeding
- knee most frequently involved, synovial hypertrophied
- hemathrosis S&S: tingling, flexion stiffness, swelling, decreased ROM, warmth, pain, protective muscle spasm
- management: factor replacement, RICE, painfree movements, pain medications
Genetic disorder
Disease caused by a variation or mutation of a gene
- mutations occur spontaneously or due to environmental factos. Some genetic disorders are inherited
- 20-30% of pediatric hospital admissions
Congenital disorder
Any anomaly present at time of birth, regardless of cause (infection, malnutrition, genes, or drug exposure)
Spinal bífida
Congenital neural tube defect
- malformation of spine, occurs very early in pregnancy
- forms: oculta (not visible), meningocele, and myelomeningocele (most serious)
Meningocele
Saclike cyst outside spine
- rare neurological deficits
Myeloeningocele
Saclike cyst outside spine
- flaccid or spastic paralysis, B&B incontinence, deformation, hydrocephalus, cognitive limitation
Erb’s palsy
Etiology: brachial plexus injury during birth (3 types)
Arthrogryposis multiple congénita
Etiology: decreased fetal movement
- can present as club foot or hip dysplasia
Multifactorial disorders
- involve a number of genes combined with environmental factors, localized area
- the interaction of genetic and environmental factos, so can be affected
- heart disease - breast and colon cancer - type 2 diabetes mellitus
Phenotype - multiple interactions
- genes
- diet
- environment
- social
- psychological
- allergens
- infection
- exercise
