Chapter 6 Flashcards
how many chromosomes results from fertilization?
23 (autosomes 1-22)
XX
girl
XY
boy
developmental disease
birth defect, congenital anomalies
where do developmental disease originate?
embryo (first 8 weeks in utero) and fetus (9 weeks-birth)
developmental disease affects..
normal maturation
how are developmental disease caused?
unknown or hereditary
genetic disease
disease caused by abnormal DNA (inherited, occur during gamete development)
classifications of developmental disease
- errors of morphogenesis (creation of genes)
- monogenetic (one gene effected)
- polygenetic (multiple genes effected)
- chromosomal
what percentage of newborns have birth defects?
3-4%
what are the causes of birth defects?
- 65% unknown
- 20% genetic
- 5% chromosomal
- 10% environmental
how many are born with serious birth defects?
250,000 (heart defect is most common)
polygenetic diseases
- many genes and environmental causes (multifactorial)
- cleft lip/palate
- spina bifida
chromosomal disease
alterations in chromosome structure or number
chromosome abnormalities are the..
- leading cause of genetic diseases
- leading cause of intellectual impairment
- leading cause of pregnancy loss
types of chromosomal changes
- aneuploidy: wrong number of chromosomes, too little or too many
- deletions: chromosome missing
- translocations: 2 chromosomes swap
non-disjunction in meiosis
chromosomes don’t separate correctly either in the first or second round
indications of genetic diseases
- mother 35 years or older
- parents who have child with known genetic disease
- family history
what are some tests to determine if determine if a genetic disease is present?
- screening tests: maternal serum screening (look for markers) not definitive, low specificity and sensitivity
- diagnostic tests: amniocentesis and chorionic villi (use cells collected from fetus)
- ultrasound
amniosentesis
injects needle into mothers abdomen to collect amniotic fluid, ultrasound is used to follow needle
amniocentesis detects..
about 1,000 of the more than 5,000 known chromosomal and biochemical problems
amniocentesis risk
pregnancy loss is 1 in 1,600
what are some recommendations in getting an amniocentesis?
- weeks 16-18
- mother 35+
- parents with known genetic disease
- family history
chorionic villi sampling (CVS)
needle goes up the vagina to get amnion from baby
- chorionic villi: projections of the placenta
when is it recommended to get a chorionic villi sample?
- 10-12th weeks of pregnancy
- earlier results than amniocentesis, but less accurate (cannot test for neural tube defects)
- greater risk of pregnancy loss (1%)
- may not be accurate if needle collected cells from mom instead of baby
what does an ultrasound exam detect?
- structural abnormalities of nervous system (anencephaly, spina bifida)
- hydrocephalus: water on brain
- obstruction of urinary tract
- failure of kidneys to develop
- failure of limbs to form normally
stages of development
- fertilization
- embryonal period = first 8 weeks after fertilization
- fetal period = weeks 9-38 (full term)
- perinatal period = two weeks before birth to one month after birth
- infancy = first year
- childhood
- adolescence = puberty
morphogenesis
creation of form
teratogens
harmful drugs and chemicals, pathogens, can cause birth defects
what are examples of teratogens?
- cigarettes
- alcohol
- radiation
- maternal infections (syphilis, rubella, herpes simplex virus)
what are the most common embryonic/fetal diseases?
congenital heart defects, early period, might not know you’re pregnant so can cause problems
- come to attention around time of birth (cyanosis and murmur)
embryonic period is also known as..
organogenesis = organs mature and develop
what are causes of embryonic and fetal diseases?
- environment (teratogens/maternal illness)
- genetic (down syndrome, phenylketonuria)
categories of drugs harmful to fetus
A = no risk
B = no evidence of risk to fetus
C = risk to fetus cannot be ruled out
D = positive evidence of risk to fetus
X = absolutely contraindicated in pregnancy
fetal alcohol syndrome
- 1:1,000 births (not rare)
- mom consumes alcohol (how much determines severity)
- fetal growth restriction, CNS abnormalities, distinctive facial features (shorter, small head, small face features, intellectual disabilities)
perinatal
“around” birth
most important cause of death in perinatal diseases is..
premature born babies
premature
- births occurring 3 weeks or more prior to full term
- calculated by gestational age (time between fertilization and birth, calculated from last day of menstrual cycle)
prematurity effects approximately..
10% of babies
does gestational age directly correlate with survival?
- 24 weeks = 50% survival
- 37 weeks = 100% survival
what are complications of premature births?
- low birth weight
- brain development
- lung development
cerebral palsy (prematurity complication)
- increased risk in premature babies
- group of disorders affecting learning, muscle tone, movement, motor skills, hearing, and seeing (nervous system didn’t develop)
- nonprogressive
major causes of infant death
- congenital and chromosomal abnormalities (born)
- prematurity and low birth weight
- sudden infant death syndrome (SIDS)
- complications of maternal diseases (diabetes)
- diseases of the placenta and umbilical cord
sudden infant death syndrome (SIDS)
unexpected, sudden death of a chiid under age 1
risk factors for SIDS
- sleeping on stomach
- being around cigarette smoke while in the womb or after birth
- sleeping in the same bed as their parents
- premature birth
- having a brother or sister who had SIDS
- mothers who use illegal drugs
- being born to a teen mother
- no prenatal care
- living in poverty situations
how do diseases of older age groups differ from childhood and adolescence?
- neoplasms less common
- not dying from heart disease
- accidents and infections more common
- some genetic diseases manifest in childhood
genetic disease
disease caused by a change in DNA sequence away from normal sequence (may be inherited from either parent, errors in meiosis or mitosis)
classifications of genetic diseases
- chromosomal disorders (number/structures)
- autosomal dominant
- autosomal recessive
- sex linked
specific genetic diseases
- down syndrome
- sickle cell disease
- marfan syndrome
- cystic fibrosis
- phenylketonuria
- duchenne muscular dystrophy
- sex chromosome
trisomy 21 (downs)
- discovered in 1866 by John Langdon Down
- now known to result from 3 chromosomes on 21
- most common chromosome abnormality
- single most common cause of genetic intellectual impairment
clinical features of down syndrome
- intellectual impairment (variable)
- round face, slanted eyes
- small stature
- congenital heart disease
- intestinal defects (colon)
- increased risk of alzheimers disease
- reduced life expectancy because of heart defects
causes/risks of down syndrome
- error in cell division (95% due to non-disjunction i meiosis 1)
- egg is source of extra 21 in 95% of cases
- main risk if moms age, older eggs are more fragile
turner syndrome (sex chromosome)
- only one sex chromosome (X)
- female phenotype
- short, webbing of neck, female internal sex organs don’t develop (infertile), never get period = no puberty, heart issues
klinefelter syndrome
- XXY
- male phenotype
- tall, no development of internal sex organs, cannot have kids, breast development (gynecomastia), nondisjunction is main cause
many hereditary diseases are transmitted on ..
autosomes
autosomal dominant inheritance
only need one copy of dominant allele
autosomal recessive inheritance
need both recessive copies
an infected person with autosomal dominant inheritance has a ..
50% chance of passing gene to child
examples of autosomal dominant inheritance
- huntingtons disease
- marfan syndrome
marfan syndrom
- defect ini collagen synthesis (found in many organs)
marfan syndrome effects..
- skeleton (tall, disproportionately long appendages)
- heart valves
- eye (retina comes detached)
- reduced life expectancy due to cardiac arrest
cystic fibrosis
- most common autosomal recessive disorder affecting caucasians (1/27 are carriers)
- mutation in chloride channel
- results in thick mucus of the lungs and effects movement of sodium
- life expectancy reduced to ~35 yrs (lung infections)
sickle cell disease
- mutation in hemoglobin (RBC) molecule, altering its shape
- more common in African-Americans and Mediterranean dissent
signs and symptoms of sickle cell disease
- anemia
- microinfarcts (small death of tissue because of lack of blood flow)
- can cause sickle cell crises (decreases blood flow of organ)
- reduced life expectancy
phenylketonuria
- DON’T drink diet pops
- mutation in phenylalanine hydroxylase enzyme absent, resulting in phenylalanine accumulation
- results in intellectual impairment
- builds up and causes toxicity in the brain
is testing of newborns for phenylketonuria mandatory?
yes
examples of X linked diseases
- duchenne muscular dystrophy
- hemophilia = disease of clotting
x-linked disease
mother is carrier of faulty copy of x-linked gene
- male with x-linked disease got it from mom
- females are often carriers because they have a backup X chromosome
- if father is infected, girls are genetic carriers and males have a chance of being carriers
duchenne muscular dystrophy
neuromuscular disease
symptoms of duchenne muscular dystrophy
- delayed development
- loss of motor skills (onset at 3 years old)
- clumsiness/frequent falls
- difficulty walking and running (wheelchair bound by 12)
- ultimately effects diaphragm (death usually occurs around 30)
when is duchenne muscular dystrophy diagnosed?
16 months to 5 yrs
