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Lecture 3

Psychology 2043A/B Lecture Notes - Lecture 3: Abusive Head Trauma, Klinefelter Syndrome, Turner Syndrome

Course Code
Esther Goldberg

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Psychology 2043B Exceptional Children: Developmental Disabilities
Week 3: Risk Factors and Children at Risk
Weekly Objectives
1. Develop an understanding of risk factors
2. Overview established risks, biological risks, and environmental risks
3. Provide some basic information about genetics and the types of genetic errors that can
4. Review the stages of foetal development and some of the major types of prenatal risk
5. Look at some of the different peri-natal and post-natal complications that can occur,
including an overview of prematurity, low birth weight, and shaken baby syndrome
6. Provide an example of one type of environmental risk factor (lead poisoning) and its
7. Discuss the differences between primary, secondary, and tertiary prevention efforts
At risk refers to infants and young children who are physically, medically, or
psychologically in danger of failing to thrive and also includes children who are affected
by diverse economic, environmental, and geographical factors
o Risk connotes a given probability but does not imply certainty, and not all
children who fall within these categories of increased vulnerability become
Risk factors are the biological or environmental causes of potential
disabilities. When children are considered to be high risk or at risk, they
are seen to be more prone to developing some form of disabling
condition or for adverse effects of school learning and behaviour
Etiology: the process of finding causes to explain how a particular
problem came into existence
Symptoms: the overt reactions or manifestations of the body to a certain
Symptomatology: the study of symptoms and characteristics
Teratology: the study of the agents involved in major congenital
Pathophysiology: the adverse effects of a condition on development
Behavioural phenotype: patterns of behaviour or characteristics
exhibited by individuals with a certain condition
We’re going to cover three types of risk:
o Established Risks genetic problems that invariably (always) lead to a
developmental issue
o Biological Risks developmental events (e.g. prematurity; exposure to toxins)
that place children at higher risk, but the outcome is not as certain

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o Environmental Risk external factors beyond a child’s control that place children
at higher risk for negative outcomes (e.g. environmental deprivation,
A Bit About Genetics
Chromosomes are the things that make organisms what they are
Chromosomes are made up of DNA (or deoxyribonucleic acid) the hereditary material
in humans and almost all other organisms
Segments of DNA in specific patterns are called genes. Your genes make you who you
In humans, each cell contains 23 pairs of chromosomes, for a total of 46
Twenty-two of these pairs, called autosomes, look the same in both males and females
The 23rd pair, the sex chromosomes, differ between males and females. Females have
two copies of the X chromosome, while males have one X and one Y chromosome
Each parent contributes one chromosome to each pair so that offspring get half of their
chromosomes from their mother and half from their father
Genetics Things Can Go Wrong…
About 1 in 150 babies in the United States is born with a chromosomal abnormality
These abnormalities are caused by errors in the number or structure of chromosomes
Many children with a chromosomal abnormality have mental and/or physical birth
Some chromosomal abnormalities result in miscarriage or stillbirth
Egg and sperm cells each contain 23 chromosomes. When they join together, they form
a fertilized egg with 46 chromosomes
Sometimes, something goes wrong before fertilization. An egg or sperm cell may divide
incorrectly, resulting in an egg or sperm cell with too many or too few chromosomes.
When this cell with the wrong number of chromosomes joins with a normal egg or
sperm cell, the resulting embryo has a chromosomal abnormality
In most cases, an embryo with the wrong number of chromosomes does not survive
Other errors can occur before fertilization. These errors can alter the structure of one or
more chromosomes. Individuals with structural chromosomal abnormalities usually
have the normal number of chromosomes. However, small pieces of a chromosome (or
chromosomes) may be deleted, duplicated, inverted, misplaced or exchanged with part
of another chromosome
Monosomy: describes the absence of one member of a pair of chromosomes (i.e 45
chromosomes in each cell of the body instead of the usual 46)
Trisomy: describes the presence of an extra chromosome
Deletion: A small section of a chromosome is missing
Translocation: A section of a chromosome is attached to another chromosome
Inversion: A section of chromosome is snipped out and reinserted upside down
Duplication: A section of a chromosome is duplicated, so there is extra genetic material

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Established Risk
The established risk category refers to medical conditions and anomalies that invariably
result in a disability or developmental delay. Established risk is most often related to
genetic and chromosomal problems
Problems may range from relatively minor through to major difficulties, called the
continuum of reproductive casualty
Genetic and Chromosomal Differences
o All individuals are born with a unique combination of genes that are theirs alone
from the moment of conception. One tiny flaw in the genetic structure can have
tragic results
Chromosomal Disorders
o Chromosomal problems result from chromosomal dysjunction, a malfunction in
cell division. Problems occur when there is an extra chromosome, or when
pieces or parts of chromosomes attach themselves to other chromosomes
o The most common chromosomal aberration is Down syndrome. Fragile X
syndrome is second only to Down syndrome among genetic abnormalities
associated with intellectual disabilities
Genetic Disorders
o There are a large number of confirmed or suspected dominant genetic disorders
that can result in mental retardation and other disabilities. Congenital
abnormalities, or hereditary abnormalities, are present at birth
o Patterns of inheritance may be dominant, recessive, or multifactorial. Some
disorders are linked to the genes on the twenty-third pair of chromosomes. In X-
linked inheritance, the sons have a fifty-fifty chance of inheriting the condition
through the mother
Inborn Errors of Metabolism
o Metabolic problems due to hereditary are termed inborn errors of metabolism.
Most inborn errors of metabolism are the result of the action of a single pair of
genes. Many result in missing or defective enzymes. The absence of, or defect in,
one of the enzymes means that the normal chemistry of a cell is altered by the
inability to provide or dispose of a critical chemical or protein, which leads to
unusual levels of particular chemicals in the body
Tay-Sachs Disease
o Tay-Sachs results from an enzyme deficiency caused by a single autosomal
recessive gene. Infants appear normal at birth, but the nervous system is
gradually destroyed because of the missing enzyme, hexosamidose A. Death is
inevitable, usually occurring between four and six years of age
Phenylketonuria (PKU)
o PKU is a problem with modifier genes-genes that act on other genes and
determine how the other genes express themselves. In PKU, the condition is
marked by an inability to normally oxidize the amino acid phenylalanine, which is
found in fish, dairy products, and most protein sources. Early screening and a
special diet eliminates or diminishes the effects of PKU
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