chap 6 - start of unit 2 Flashcards
frequency and significance of genetic and developmental diseases
3-4% of newborns have birth defects
- causes
65% unknown
20% genetic
5% chromosomal
10% environmental
- 250,000 born with serious birth defects
- half of all miscarriages due to chromosome abnormalities
developmental disease
birth defect
- orginating in the embryo and fetus, disease affects normal maturation,
genetic disease
disease caused by abnormal DNA, inherited, occur during gamete development
errors of morphogenesis
due to genetics, environmental or teratogens
teratogens
harmful drugs and chemicals that will cause harm to developing fetus
ex: cigarettes, alcohol, radiation, maternal infections, rubella, herpes simplex virus
fetal alcohol syndrome
1:1000 births
- mom consumes alcohol - how much determines the severity
- fetal growth restriction, CNS abnormalities, distinctive facial features
monogenetic
single gene, classified as: autosome or sex chromosome, dominant or recessive
examples: sickle cell anemia, cystic fibrosis
polygenetic
many genes plus the environment
- multifactorial
examples: cleft lip and cleft palate, spina bifida
chromosomal
wrong number or wrong structure of the chromosomes
- karyotype useful for visualizing - mapping out of the chromosomes
- alterations in chromosome structure or number
chromosome abnormalities
- leading cause of genetic disease
- leading cause of intellectual impairment
- leading cause of pregnancy loss
types of chromosomal change
aneuploidy, deletions, translocations
aneuploidy
having the wrong number, can be detected in an amniocentesis and chorionic villus sampling - because these take cells from the fetus
nondisjuction
the chromosomes don’t pull apart like they should
- can occur in either the egg or the sperm
stages of developmentt
fertilization - embryonic period - fetal period - perinatal period - infancy - childhood - adolescence
embryonal period
first 8 weeks after fertilization
fetal period
weeks 9-38, organs mature and get bigger, most sensitive to teratogens because that is when the organs are developing
perinatal period
two weeks before birth to one month after birth
infancy
the first year of life
childhood
after a year old up until puberty
organogensis
organs are formed
when does organogenesis occur?
embryonic perriod
most common embryonic and fetal diseases
congenital heart defects
- often come attention around the time of birth
- cyanosis, murmur
cyanosis
blue lips, blue fingernail bed, the oxygenated and deoxygenated blood mix together due to defect within the heart
perinatal diseases
“around birth”
- prematurity most important cause of death
complications - low birth weight, brain development, the lungs are also the last to develop
prematurity
gestational age correlates directly with surivial
prematurity complication examples
cerebral palsy
cerebral palsy
associated with gestational age in some cases
- group of disorders affecting learning, muscle tone, movement, motor skills, hearing and seeing
nonprogressive
diseases of infancy
major causes of infant death:
- congenital and chromosomal abnormalities
- prematurity and low birth weight
- sudden infant death syndrome
- complications of maternal diseases
- diseases of the placenta and umbilical cord
sudden infant death syndrom
unexpected, sudden death of a child under age 1
risk factors
- sleeping on the stomach
- being around cigarette smoke before or after birth
- cosleeping
- premature birth
- having a sibling who had SIDS
- mothers who use illegal drugs
- being born to a teen mother
- no prenatal care
- living in poverty situations
diseases of childhood and adolescence
differ from diseases of older age groups in relative frequency
- neoplasms less common
accidents and infections more common - most common cause of death for children under 5 is accidents
- some genetic diseases manifest in childhood
amniocentesis
detects about 1,000 of the more than 5,000 know chromosomal and biochemical problems, ultrasound is used to follow needles movement
risk - some pregnancies are lost
recommended for = fetus around 15-16 weeks
chorionic villi sampling
chorionic villi = projections of the placenta
performed during 10-12th week of pregnancy
- earlier results from amniocentesis
- less accurate than amniocentesis
- does not test amniotic fluid
- cannot test for neural tube defects
- placental mosaicism
- greater risk of pregnancy loss
ultrasound
detection of major structural abnormalities
genetic disease
disease caused by a change in DNA sequence away from the normal sequence
- may be inherited from either parent
- errors in cell division, meiosis or mitosis
classifications: chromosomal disorders, autosomal dominant, autosomal recessive, and sex linked
examples of genetic diseases
down syndrome, sickle cell disease, marfan syndrome, cystic fibrosis, phenylketonuria, duchenne muscular dystrophy
down syndrome
trisomy 21
- most common chromosome abnormality
- single most common cause of genetic intellectual impairment
- error in cell division
- 95% due to nondisjunction meiosis I
- egg is source of extra 21 in 95% of cases
main risk: maternal age
clinical features of down syndrome
- intellectual impairment - variable
- round face, slanted eyes
- congenital heart disease
- intestinal defects
- shorter life expectancy
- increased risk for alzheimer’s disease
turner syndrome
sex chromosome abnormality
- 45, X
female phenotype
characteristics –> shorter in stature, webbing in the neck, no intellectual impairment, the internal sex organs do not develop correclty, not uterus, ovaries, they will also be sterile
- this is because X wasn’t pulled apart correctly so they only have the 1 X chromosome
aneuploidy
klinefelter syndrome
XXY - an extra X copy in a male
male phenotype
- characteristics –> typically taller then normal, long extremities and digits, can have breast development, will be sterile because they don’t have normal production of sperm
autosomal dominant inheritance
gene is expressed if only one copy is present
- one allele is dominant
an affected person has a 50% chance of passing gene to child
examples = huntington’s disease and marfan syndrome
marfan syndrome
defect in collagen synthesis, several different systems are affected
- skeleton = tall, long appendages and extremities
- heart valves = dont snap shut tightly, also impacts the blood vessels, they might not be strong enough against the pressure of blood vessels
- eyes - retina can detach in the back of the eye
autosomal recessive inheritance
need two copies of the defective gene
- parents of affected are usually heterozygous carriers
cystic fibrosis
most common AR disorder affecting caucasians - very common to be a carrier as well
- mutation in the chloride channel
- results in: mainly affects the lungs and GI tract - lack of movement of chloride decrease the movement of sodium which in result decreases the water movement of the lungs, mucus in the lungs gets thick and sticky and can clog up the bronchioles which can increase the chance of infection
- low life expectancy –> reduced down to their 30s
sickle cell anemia
mutation in hemoglobin molecule, altering its shape - more likely to clump and stick together which can cause blockages to organs, simple change to a base in the DNA
phenylketonuria
mutation in phenylalanine hydroxylase enzyme absent, resulting in phenylalanine wants to convert to tyrosine but needs phenylalanine hydroxylase to do so
- results in intellectual impairment
- treatment => avoiding phenylalanine, testing in newborns mandatory in all 50 states
sex linked inheritance
x chromosome is large
x linked diseases are mutations carried on the X chromosome
duchenne muscular dystrophy
symptoms usually present around 3 years of age
- delayed development
- loss of muscular skills
- clumsiness/frequent falls
- difficulty walking and running - wheelchair bound by 12 years
- ultimately effects diaphragm - death usually occurs around 30
- diagnosis typically around 16 months - 5 years
