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Genes & Heredity
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How the affect development in children
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What are Chromosomes, DNA and Genes? How are
these structures different and how do they function
to determine our genetic codes?
How do environment and genetics work together?
What is the purpose of genetic counseling?
Which human characteristics are significantly
influenced by heredity?
How is intelligence determined?
What happens during the prenatal stages of
development?
What are the threats to fetal environment?
Unit Questions
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Each of us began as a single cell- a fertilized
egg cell which multiplied into trillions.
Genes are molecules that govern the structure
and function of every cell in your body.
Genes and Human
Reproduction
The Biology of Heredity
Father’s sperm +
(gamete)
Mother’s egg
(gamete)
46 chromosomes total
• 23 from each parent
Meiosis: the biological process of cell division resulting in gametes that have 23 chromosomes,
which is half the amount of genetic material normally seen in a human cell.
Mitosis: the biological process of cell division resulting in bodily cells that are exact copies of
their parent cells and have a full set of 46 chromosomes.
In-vitro fertilization: an artificial form of egg fertilization in which sperm and egg are united in a
laboratory dish.
The Biology of Heredity
The first 22 pairs of chromosomes are autosomes
and the 23rd pair are sex chromosomes.
 Chromosomes consist of DNA which codes for
proteins and enzymes.
 Genotype is one’s complete set of genes and
phenotype is one’s physical, behavioral, and
psychological features.
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Less than 3% of pregnancy produce twins
Monozygotic twins are genetically identicalThe egg is split so fetus shared genetic code.
Dizygotic twins not genetically identical- Two
eggs are fertilized by two separate sperm. They
are genetically independent.
Multiple Births
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What determined the color of your hair? Why
are you tall or short? Why do you have so
many freckles?
Mixing and Matching of Traits
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Genotype- The underlying combination of
genetic material present in an organism
Phenotype- An observable trait, the trait that is
actually seen.
Homozygous- Inheriting from parents similar
genes and traits
Polygenic Inheritance- Inheritance in which a
combination of multiple gene pairs is
responsible for the production of a particular
trait
Transmission of Genetics
Inherited Disorders
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Inherited disorders that affect development are usually triggered
when a child inherits two recessive alleles.
Examples include Albinism, Cystic fibrosis, PKU, and Tay-Sachs
disease.
Most inherited disorders are very rare.
Abnormal Chromosomes
Some people are born with too many, too few, or
damaged chromosomes.
 People with Down Syndrome usually have an
extra 21st chromosome.
 Damaged autosomes always affect development
because autosomes contain so much genetic
material.
 A number of disorders are caused by missing or
extra sex chromosomes (see Table 3-5).
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Downs Syndrome is a disorder produced by
the presence of an extra chromosome on the
21st pair.
It is the most frequent cause of mental
retardation.
Downs Syndrome
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Occurs when a particular gene is injured on the
X Chromosome.
Causes mild to moderate retardation
Fragile X Syndrome
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1/10 of African Americans population carries
the gene that produces the disorder.
Symptoms include poor appetite, stunted
growth, swollen stomach and yellowish eyes.
Those affected with severe cases do not live
past childhood
A blood disorder that gets its name from the
shape of the red blood cell.
Sickle Cell Anemia
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One out of every 400 males is born with it
It is the presence of an extra X chromosome
The XXY complement produces
underdeveloped genitals, extreme height, and
enlarged breasts.
It is an abnormalities that is the result of
receiving the improper number of sex
chromosomes.
Klinefleter’s Syndrome
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Occurs mainly in Jews from eastern European
ancestry and in French Canadians.
May cause death before its victims reach school
age
There is no treatment for this disorder that
produces blindness and muscle degeneration
Tay-Sachs Disease
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Genetic Counseling focuses on helping people
deal with issues relating to inherited disorders
They use data such as family history, blood
tests, urine tests and physical examinations to
help determine presence of abnormalities
Prenatal testing in the form of ultra sound,
amniocentesis and chronic villus sampling to
determine genetic abnormalites
Genetic Counseling
Behavioural Genetics
The study of the inheritance of behavioral and
psychological traits.
 Many behavioural genotypes reflect polygenic
inheritance, which involves many genes.
 Behavioural geneticists rely upon twin studies
(monozygotic and dizygotic) and adoption studies.
 Intelligence, psychological disorders (i.e. depression
and schizophrenia),and personality
(introversion/extroversion) are all strongly affected by
heredity.
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The Nature of Nurture
Parents don’t provide exactly the same environments for all of their children
(non-shared environmental influences).
– Non-shared environmental influences
 Experiences unique to individual, not shared by other members of
family in same environment.
– Shared environmental influences
 Experiences common to all family members in same environment.
Parents provide the child’s genes and environment, but the child also
influences her own environment.
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The family environment is important, but it
usually affects each child in unique ways,
which makes siblings differ.
Families create multiple, unique environments
for each child in the household.
The Nature of Nurture
Paths from Genes to
Behaviour
Genes never cause behaviour
directly.
The behavioural consequences of
genetic instructions depends on the
environment.
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Changing Relations between
Nature and Nurture
Passive gene-environment relation: parents pass on
genotype and environment.
 Evocative gene-environment relation: different
genotypes evoke different responses from the
environment.
 Active gene-environment relation: actively seek
environments related to their genes.
 Niche-picking: the process of deliberately selecting an
environment suitable to one’s genotype.
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The Relation Between Genes
and Environment
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GERMINAL STAGE- Fertilization to 2 wks
EMBRYONIC STAGE- 2wks to 8 wks
FETALS STAGE- 8wks to Birth
https://youtu.be/gaK0VPV9NlE
What happens during prenatal stages of
development
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Fertilization to 2 weeks
The first and shortest stage of prenatal period
During the first two weeks the fertilized egg
moves toward the uterus where it will become
implanted
A Placenta is formed. Placenta is a conduit
between mother and fetus that provides
nourishment and oxygen through the umbilical
cord.
Germinal Stage
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2 weeks to 8 weeks
The embryo is securely attached to the uterine
wall
Development of major organs and basic
anatomy take place during this stage
Ectoderm (skin, hair, teeth),
endoderm(digestive system, liver, pancreas,
respiratory system) and mesoderm(muscles,
bones, blood) are developed
The Embryonic Stage
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8 weeks to Birth
Starts when the differentiation of the major
organs occur
The developing child is becoming rapidly more
complex
Fetus becomes active
The brain starts to develop lobes.
Neurotransmitters become more complex
Hormones are released
The Fetal Stage
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Infertility can become a problem for those
wanting to get pregnant. Many may try
artificial insemination or in vitro fertilization.
Miscarriages occur in 15-20% of all
pregnancies. They are often in relation to
genetic abnormalities
Pregnancy Problems
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Birth defects may be caused by more than
genetic abnormalities. There are environmental
factors or social economic factors that may
cause birth defects as well.
Teratogens are environmental agents such as
drugs, chemicals or virus’ that may cause birth
defects
Pre-natal environment
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Diet
Pregnant mothers should eat a diet high in
nutrients this will ensure easier labor and
healthier babies
Prenatal supplements and vitamins can counter
affects of malnourishment
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Age
Women who give birth over the age of 30 risk
complications during pregnancy and birth.
Children are more likely to have lower birth
weights or prematurely
They run a higher risk of having children being
born with Downs Syndrome
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Generally causes a high mortality rate in babies
for adolescent mothers
Factors such as social and economic influences
can affect infant death
Many teenage mothers do not have money or
support for proper prenatal care
Prenatal Support
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Mothers who eat the right foods, maintain an
appropriate weight and exercise regularly
maximize the changes of have a healthy baby
Illnesses such as chicken pox or mump in a
mother can have devastating consequences
Some sexually transmitted diseases can be
transmitted directly to the fetus who will suffer
and be born with the disease
Health
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Read Article and Answer questions
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https://youtu.be/3k6TwvSE-iI
Drug and Alcohol Abuse
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Complete Case Study on Melindah and Jermain
Tessel
Case Study