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Concept Dis. Ch. 9

Congenital & Hereditary Diseases

present at birth congenital
presence of extra chromosome within a cell trisomy
an example of trisomy is having three of a given pair of chromosomes instead of usual pair
condition of a cell in which one chromosome of homologous pair is missing monosomy
nondisjunction can lead to the chromosomal abnormalities of trisomy & translocations
individuals with Turner's syndrome have chromosomes of the configuration 45, X
Triple X syndrome can be associated with decreased mental capacity
Fragile X syndrome is a major cause of mental deficiency
x-linked autosomal diseases can become symptomatic in males
trisomy of 12 autosomes will not be compatible with full-term pregnancy
depending on genetic makeup, an embryo will be more or less susceptible to malformation from environmental factors
culture of amnionic cells is important in order to determine karyotype
chorionic villus sampling provides the same information as amniocentesis
transfer of piece of one chromosome to a nonhomologous chromosome translocation
congenital syndrome usually caused by absence of one X chromosome in the female Turner syndrome
congenital syndrome caused by extra X chromosome in male Klinefelter syndrome
Klinefelter syndrome is characterizes by testicular atrophy, sterility, feminine body configuration, & subnormal intelligence
congenital syndrome caused by extra chromosome 21 Down syndrome
change in structure of gene, which may alter its functions gene mutation
abnormal hemoglobin that crystallizes under reduced oxygen tension sickle hemoglobin
congenital malformation; absence of brain, cranial vault, & scalp as result of defective closure of neural tube anencephaly
incomplete closure of vertebral arches over spinal cord spina bifida
protrusion of meninges & neural tissue through spina bifida defect cystic spina bifida
protein produced by fetal liver early in gestation alpha fetoprotein
alpha fetoprotein is also sometimes produced by tumor cells
alpha fetoprotein level is elevated in amniotic fluid when fetus has neural tube defect
one X chromosome is inactivated Lyon Hypothesis
in males one copy of most genes is on X chromosome, & inheritance of these genes is called X-linked
man will transmit one copy of each X-linked gene to his daughters and none to his sons
a woman will transmit one copy of each X-linked gene to each daughter or son
environmental factors can affect expression of some genes
examples environmental factors that can influence a child's development include: nutritional patterns and health care
result from abnormalities of individual genes on the chromosomes genetically determined diseases
some abnormalities of individual genes on the chromosomes, arise spontaneously, while others may be caused by environmental teratogens
any agent or factor that induces or increases the incidence of abnormal prenatal development teratogen
permanent transmissible change in genetic material, usually in single gene, although sometimes used to include gross alterations in chromosomal structure mutation
caused by abnormalities in an individual’s genome genetic or hereditary disorders or diseases
any abnormality present at birth congenital disease or malformation
chromosomal abnormalities, abnormalities of individual genes, intrauterine injury, or environmental factors factors in congenital malformations
2-3% of all newborn infants have congenital defects
additional 2-3% of developmental defects are demonstrated later as infants grow older
25% to 50% spontaneously aborted embryos, fetuses, and stillborn infants have major congenital malformations
failure of homologous chromosomes in germ cells to separate in first or second meiotic division nondisjunction
nondisjunction may involve either sex chromosomes or autosomes
nondisjunction causes abnormalities in distribution of chromosomes between germ cells
in nondisjunction, one of two germ cells has an extra chromosome while the other lacks a chromosome
chromosome breaks during meiosis and broken piece is lost deletion
variations in normal number of sex chromosomes are often associated with some reduction of intelligence
directs masculine sexual differentiation, associated with male body configuration regardless of number of X chromosomes present Y chromosome
no significant effect as it mainly carries genes concerned with male sexual differentiation extra Y chromosome
body configuration is female absent Y chromosome
has little effect (one X chromosome is inactivated) extra X chromosome
has adverse effects on male development extra X chromosome in males
extra X chromosome Triple X Syndrome
extra Y chromosome XYY Syndrome
most common chromosome abnormalities, in the female Turner Syndrome & Triple X Syndrome
most common chromosome abnormalities, in the male Klinefelter’s Syndrome & XYY Syndrome
Fragile X Syndrome causes x-linked mental deficiency
not related to either excess/deficiency of sex chromosomes & associated with a characteristic abnormality of X chromosome Fragile X Syndrome
as a major cause of mental deficiency Fragile X Syndrome is second to Down syndrome
results in the loss of several genes that development is generally not possible and the embryo is aborted absence of an autosome
may be compatible with development but usually results in multiple severe congenital abnormalities deletion of a small part of an autosome
most common chromosomal abnormality, an autosomal trisomy Down syndrome
Down syndrome is an autosomal trisomy of small chromosome 21
in Down syndrome extra chromosome 21 acquired as part of the translocation chromosome
most common chromosomal abnormality: 1:600 births/manifestations: mental deficiency, cardiac malformation, major defects in other organ systems nondisjunction occurring in zygote
Cleft lip and palate; abnormal development of skull, brain, and eyes; congenital heart defect; polydactyly is caused by trisomy of chromosome 13
associated with multiple severe congenital abnormalities trisomy of chromosome 18
are usually fatal in the neonatal period or in early infancy both 13 and 18 trisomies
leads to formation of gametes with an extra or missing chromosome. nondisjunction in meiosis
occurs in small number of persons with Down syndrome translocation Down syndrome
in translocation Down syndrome ___ fused with chromosome 14 or another chromosome chromosome 21
in translocation Down syndrome total number of chromosomes not increased but genetic material is equivalent to 47 chromosomes
translocation Down syndrome translocation occurred accidentally during gametogenesis when both parents have normal chromosome cells
parent is capable of transmitting abnormal chromosome to his or her children resulting in translocation Down syndrome 14/21 carrier in one of the parents
translocation chromosome is not always transmitted normal fetus, child becomes carrier, nonviable fetus, Down Syndrome can occur when female carrier
most hereditary diseases are transmitted on autosomes
few hereditary diseases are carried on sex chromosomes
autosomal dominant inheritance, autosomal recessive inheritance, codominant inheritance, X-linked inheritance are all possible for transmission of genetically determined diseases
3rd–8th week after conception: embryo is most vulnerable to ___ ___ as organ systems are still forming maternal infections
combined effect of multiple genes interacting with environmental agents multifactorial inheritance
test to determine biochemical abnormalities in fetal cells i.e.: chromosomal abnormalities, biochemical abnormalities, analysis of DNA examination of fetal cells
tested because products secreted into fluid by fetus that may indicate fetal abnormality examination of amniotic fluid
test used to detect major structural abnormalities, i.e. structural abnormalities of nervous system, hydrocephalus, obstruction of urinary tract, failure of kidneys to develop, failure of limbs to form normally ultrasound examination
examples of major structural abnormalities of nervous system anencephaly &; spina bifida
determination of biochemical abnormalities by analysis of DNA of fetal cells fetal DNA analysis
tests used to determine fetal DNA analysis amniocentesis & chorionic villus sampling
amniotic fluid for study, usually performed between the 14th and 18th week of pregnancy transabdominal amniocentesis
prenatal detection of chromosomal abnormality in women over age 35 due to higher incidence of Down syndrome in infants born to older women primary use of transabdominal amniocentesis
frond-like structures that form part of placenta and attach to lining of uterus Chorionic villi
can be performed earlier than amniocentesis & carries less risk from abortion if parent decides to terminate pregnancy in case of congenital abnormality advantages of chorionic villus sampling
more difficult technically than amniocentesis & complications include spontaneous abortion, limb deformities in fetus disadvantages of chorionic villus sampling
Created by: lfrancois