Congenital and Hereditary Disorders

congential disorders

conditions that present in an individual at birth but not necessarily manifested until later in life

hereditary disorder

have the potential to be passed down from one generation to another

recessive disorder

required 2 recessive alleles to be affected; one recessive allele to be a carrier

dominant disorder

requires only one allele to be affected, no carriers 

allele

chromosomes with a function at a specific location

autosomal disorder

the gene affected is located on one of the numbered chromosomes 

chromosomal anomalies

error during meiosis, number/distribution of chromosomes are altered

genotype

genetic information carried by the individual (pairing of alleles), not all genes are expressed in all cells

phenotype 

how the gene is expressed (brown or blue eyes) 

heterozygous

alleles are different versions from each parent

homozygous

alleles are the same from each parent

genetic control 

genetic info is stored in chromosomes, 23 pairs in humans (22 autosomes, one pair of sex) 

karyotype

visual representation of chromosomes arranged in order of size, used in diagnosis of chromosomal disorders

why is karyotyping performed

count the number of chromosomes, look for structural changes in chromosomes

what tissues are used for karyotyping 

amniotic fluid, bone marrow, blood, organ tissue 

what treatment may affect the results of karyotyping

chemotherapy may cause chromosome breaks

congenital disorders

present at birth, inherited or developmental, (teratogenic agents cause damage in fetal development, single-gene expression, chromosomal defect) 

single-gene disorders

trait controlled by one set of alleles, passed down through generations, single gene controls a specific function (color blindness) or systemic effects (CF)

chromosomal anomalies

usually caused by an error during meiosis

multifactorial disorders

may be polygenic or result of inherited tendency expressed after exposure to certain environmental factors 

autosomal recessive disorders

both parents must pass on the allele for the disorder, parents may be carries or affected, heterozygous child is carrier, homozygous child has disorder

autosomal dominant disorders 

inheritance of one allele causes disorder, only one parent needs to carry allele, no carriers, some conditions are present later in life 

multifactorial disorders examples

cleft lip and palate (combination of genes and environmental factors like what mother eats, drinks, and medications) and congenital hip dislocation (mechanical risk factors as well like high birth weight, breech position, lax ligaments), congenital heart disease, type 2 diabetes)

chromosomal disorders

involves extra or missing chromosomes

trisomy 

three chromosomes rather than 2 (down syndrome) 

monosomy

only one sex chromosome present (turner syndrome)

polysomy

an extra X chromosome present (Kinefelter syndrome)

turner syndrome 

one X sex chromosome, affects females, short stature, webbed neck, infertility due to lack of ovaries 

Klinefelter syndrome

extra X chromosome, sperm is not produced

down syndrome

trisomy 21, increased risk with higher maternal age, presents with small head, round and flat face, large tongue, small hands, shorter, muscle hypotonic, loose joints, delayed development stages, cognitive impairment (mild to aggressive)