Transcript A Child’s World: Infancy Through Adolescence

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Forming a New Life:
Conception, Heredity, and
Environment
Chapter 2
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Guideposts for Study
 1. How are birth defects and disorders
transmitted?
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Mechanisms of Heredity
 Genetic and Chromosomal Abnormalities
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Some defects are due to abnormalities in
genes or chromosomes, which may result
from ________________
Many disorders arise when an inherited
predisposition interacts with an environmental
factor, either before or after birth
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Mechanisms of Heredity
 Genetic ____________________

A chart called a _______________ can show
chromosomal abnormalities and can indicate
whether a person who appears normal might
transmit genetic defects to a child
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 Should genetic counseling be compulsory
before marriage?
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Defects Transmitted by Dominant
Inheritance
 ____________ genes are usually dominant
 When one parent has a dominant abnormal
gene and one recessive normal gene and the
other parent has two recessive genes, each
of their children has a 50:50 chance of
inheriting
 Example – ___________________disease
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Defects Transmitted by Recessive
Inheritance
 _____________ defects are expressed only if
a child receives the same recessive gene
from each biological parent
 Defects transmitted by recessive inheritance
are more likely to be __________ at an early
age
 Example – _________________
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Cystic fibrosis
 Body makes too much _______________
 Children do not grow normally
 Usually do not live beyond age ________
 Most common inherited lethal defect among
________________ people
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Duchenne’s Muscular Dystrophy
 __________disease usually found in males
 Marked by muscle weakness, minor mental
retardation
 Respiratory failure and death usually occur in
______________ adulthood
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Spina Bifida
 Incompletely closed spinal canal, resulting in
muscle weakness or paralysis and loss of
bladder and bowel control
 Often accompanied by ________________
which is an accumulation of spinal fluid in the
brain (may lead to mental retardation)
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Sickle-cell anemia
 Deformed, fragile ________ blood cells that
can clog the blood vessels – deprives the
body of _____________
 Symptoms include severe pain, stunted
growth, frequent infections, leg ulcers,
gallstones, susceptibility to pneumonia, and
stroke
 Found among ______________ descent
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Tay-Sachs Disease
 Degenerative disease of the brain and nerve
cells
 Results in death before age ______
 Found among people of European
___________ descent
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Defects Transmitted by Sex-Linked
Inheritance
 Sex-linked inheritance: Pattern of
inheritance in which certain characteristics
carried on the X chromosome inherited from
the mother are transmitted differently to her
male and female offspring.
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Chromosomal Abnormalities
 Down syndrome: Chromosomal disorder
characterized by moderate to severe mental
retardation and a downward sloping skin fold
at the inner corners of the eyes. Also called
_________________________
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Sex Chromosome Abnormalities
 Fragile X
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Minor-to-severe mental retardation
Symptoms more severe in ______________
Include delayed speech and motor
development, speech impairments,
hyperactivity
The ___________ common inherited form of
mental retardation