Download 1 Heredity Influences Prenatal Development Heredity and Genetics

Heredity Influences
Prenatal Development
Chapters 3 & 4
Heredity and Genetics
„
Genotype
{
„
Actual genetic material
Phenotype
{
Expressed characteristics (the
phenomenon that appears)
Genetic Transmission
„
Cells, Nucleus, Chromosomes, DNA, Genes
„
Zygote
{
Single cell formed from the union of a sperm and an ovum
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Heredity
„
„
Over 65 trillion combinations of
chromosomes
Siblings
Heredity (cont’d)
„
Monozygotic vs. Dizygotic
What do Genes do?
„
Blueprints for development
„
Environmental factors
{
{
May affect how genes are expressed
(phenotype)
Example
2
How are Genes Expressed?
„
Five main ways:
1) dominant-recessive
2) codominance
{ 3) sex-linked
{ 4) genetic imprinting
{ 5) polygenic
{
{
„
Allele
{
Alternate forms of a gene
Dominant-Recessive
Inheritance
„
Homozygous
{
„
Identical alleles for attribute that are
identical in their effect
Heterozygous
{
{
Different alleles
for attribute that
have different
effects
Dominant vs.
Recessive (e.g., AO combination)
Blood Type
Mother (AO)
A
O
A
AA
OA
B
AB
OB
Father (AB)
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Polygenic Traits
„
Polygenic traits
{
{
Influenced by
action of many
genes
E.g., skin colour
Chromosomal Abnormalities
„
Sex Chromosome
23rd pair
XX or XY
{ Turner’s, Poly-X, Klinefelter’s
{
{
Chromosomal Abnormalities
(cont’d)
„
Sex chromosome (cont’d)
{
Turner syndrome
„
One X chromosome
4
Chromosomal Abnormalities
(cont’d)
„
Autosomal abnormality
{
Down Syndrome (DS)
„
Extra 21st chromosome
The Period of the Zygote
„
„
First two weeks of life
Fertilization to
implantation
The Period of the Embryo
„
„
Third to eighth
week
Three structures
develop to
protect and
sustain embryo
{
Amniotic sac,
placenta, and
umbilical cord
5
The Period of the Embryo
(cont)
„
Three cell layers
{
{
{
„
Ectoderm
Mesoderm
Endoderm
Fourth or fifth week
formation of neural tube
(brain and spinal cord)
The Period of the Fetus
„
„
Third month to birth
Third month
{
{
„
„
Rapid organ growth
Sexual differentiation
The second trimester
The third trimester
{
{
"Finishing phase"
Age of viability ~28 weeks
Environmental Influences on
Prenatal Development
„
Teratogens
{
Any disease, drug, or other
environmental agent that
can harm a developing
embryo or fetus
Maternal age
Diet
„ Alcohol
„ Cigarette smoking
„ Illicit drugs
„ Pollution
„
„
6
General Principles that Guide the
Effect of Teratogens
„
1. Effects exerted
during critical or
sensitive periods
„
2. Each teratogen
exerts certain
specific effects
{
{
Rubella
Alcohol
General Principles that Guide the
Effect of Teratogens (cont’d)
„
3. Maternal or fetal genotype may
counteract teratogen’s effects
„
4. Effects of one teratogen may
intensify effects of another
General Principles that Guide the
Effect of Teratogens (cont’d)
„
„
5. A teratogen may affect child but have
no discernible effect on mother
6. One teratogen → different deviations
Several teratogens → same deviation
7
General Principles that Guide the
Effect of Teratogens (cont’d)
„
7. Longer exposure and greater
intensity of teratogen, more likely the
harm
Being Born…
„
Once thought to be horribly traumatic
{
Triggers
adaptive
release of
stress
hormones
Newborn Reflexes
„
„
Involuntary
Ensure survival
{
{
Rooting and
sucking
Eye blink,
withdrawal
8
Newborn Reflexes (cont’d)
„
Primitive
{
{
{
{
„
Remnants of
evolution
Babinski
Palmar
Moro
Presence indicates normal
neurological development
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