Lecture 2 Heredity, the Brain, and Prenatal Developmen Flashcards
what is a genotype?
genetic material an individual inherits
what is a phenotype?
observable expression of genotype, including body characteristics and behaviour
what is an environment?
includes every aspect of the individual and his or her surroundings, other than genes
what is a chromosome?
threadlike structure found in the nucleus
what is DNA?
double-stranded molecule that makes up the chromosomes
what are genes?
- basic units of heredity
- each chromosome has thousands of genes, small segments of DNA
- a gene is expressed if it has been turned on to make its specific protien
what did every person start out as?
1 cell ( which we refer to as a ZYGOTE)
What is a zygote made up of?
It is basically a singular cell which is made up of sperm ( 23 chromosomes) and ova ( 23 chromosomes)
- each parent contributes half to the makeup of the zygote
What are alleles?
when the same gene has many different forms
the effect of any gene or set of genes is …
probabilistic
what is phenotypical plasticity?
the degree to which environmental factors affect a given trait
what is canalization?
when certain characteristics are restricted in their outcome, even if the environment varies widley; to summarize, they’re a less likely to get influncs to variations in the environment ( like language for an example)
what is norm of reaction?
range of possible phenotypes for a given genotype
what is epigenetics?
complex process which environment shapes the expression of genes
what are the four ways in which genes and the environment react?
- environmental factors turn genes on/off
- environmental factors alter magnitude of genetic effects on development
- gene expression can affect how people respond to children “evocative”
- Genotype affects the type of environments the person seeks out - “active”
what are the basic units of the brain
- neurons
- synapses
- glia
what are neurons
communication cells
what are synapses
connectie spaces between neurons
what are gila
suppoting cells that produce myelin
whats a myelin
a sheath that allows electrical impulses to transmit quickly and efficiently along the nerve cell
what are the four lobes of the cerebral cortex
- frontal lobe ( movements, attention impulses )
- parietal lobe ( touch, pain, and body position
- occipital lobe ( visual cortex)
- temporal lobe ( smell, taste, hearing, and language)
Explain the stages of brain development
- Neurulation ( formation of neural tube)
- Neurogenesis ( birth and migration of neutrons)
- Circuit formation (synaptogenesis and synaptic pruning )
- Myelination ( formation of fatty covering on axons)
explain Neurulation
- happens 3 weeks after conception
- neural tubes form from ectoderm
- cells inside the tube the (CNS) central nervous system cell outside the tube from the (PNS) peripheral nervous system
explain neurogensis
- the proliferation of neurons through cell division
a ) this begins as soon as the neural tube starts to form and is complete by the 18th week
b) 100 billion before birth - during this stage neuron migration mappesn where neurons move to appropriat place in the brain
explain the third stage of brain developemt circuit formation
- synaptogensis takes place whihc is most rapid in pre and postnatal periods. lots of overproduction of spynapses are producded than the amount that twill acc be used
- the peak amt of synapses happens at diff times around diff brain regions ( like during adolesence the visual corext will lower and prefrontal corext will be in peak)
- synapse pruning also happens at this stage. it is where experince determines whihc synapses will live or die ( kind of like use it or lose it) the time of pruning also varies across brain regions) like a two yearold will have more acticty than a six yearold
explain myelination
- the variability in timing across brain regions ( this is related to when you develop certain skills)
- motor and visual circuits myelinated in infancy
- frontal mylination contunies until adolsecnes or adulthood
what can interfere with mylination
nutritional deficiencies
the timing of brain develoment differs for ….
diff brain
what is developmemntal plasticty?
how much brain development is open to modification by the environment
what does the effect of an experince on the brain depend on?
- timing
- dose
- duration
how does experince influence the developing brain?
experience expectence plasticty
what is experience expectence plasticty
The brain adapts in response to existing sensory
information (species-typical experiences)
– Due to pruning of synapses that were overproduced
– Sensitive periods
provide an example of experinece plasticy
- Vision – babies born with cataracts
– Language – Genie
what are Critical periods?
A very narrow period during which a particular
experience must occur for development to proceed
normally
give an example of a critical period
Imprinting in chicks
whats a Sensitive period?
A developmental stage during which the brain is most susceptible to experiences, but changes are still possible
outside of this window
what is Experience-dependent plasticity?
– Changes in the brain due to an individual’s unique
personal experiences
– Due to formation of new synapses throughout the
lifespan
what is an example of experience dependent plasticty
– Adult violin players
– London cab drivers
what is Prenatal Development
Conception to birth
* Begins when sperm penetrates egg
and forms a zygote
* Zygote has full complement of genetic
material, half from each parent
* Takes about 266 days for the one-celled
zygote to become a fetus of 200 billion cells
what are the 3 stages of Prenatal Development
1.Germinal period (days 0-14)
- Embryonic period (weeks 3 – 8)
- Fetal period (week 9 – birth)
what is the embryonic period
(weeks 3 – 8)
– Formation of major organs
– Formation of major organs
whats germinal period
is days 0-14
– From conception to implantation in uterine wall (zygote)
whats the fetal period
(week 9 – birth)
– Organ systems begin to function
– Significant growth
what are some milestones during gerninal period
- Zygote travels towards
uterus - Cleavage:
– The division of the zygote
into many cells
– Begins ~24 hours after
conception
– Occurs while the zygote
travels down the fallopian
tube towards uterus - By the 4th day after conception, the
zygote arranges itself into a hollow
sphere of cells (the blastocyst) with a
bulge of cells, the inner cell mass, on
one side.
*Blastocyst implants in uterine wall:
–Inner layer (embryonic disc) becomes embryo
–Outer layer (trophoblast) becomes:
*Amniotic sac
*Placenta
*Umbilical cord
what are some milestones during Embryonic Period
- Cephalocaudal
development - Proximo-distal
development
– 3
rd week
* Neural tube (from ectoderm) becomes the brain and
spinal cord; major areas of the brain begin to divide
– 4
th week
* Heart begins beating; limbs, eyes, ears, and digestive
system begin to form
– 5
th week
* Lungs begin to form
– 6
th week
* Head becomes dominant; brain is differentiated
– 7
th week
* Nerve cells form in the brain; muscles differentiate;
sexual differentiation
– 8
th week
* Ears are fully formed; fetus is capable of moving
What does folic acid
have to do with prenatal
development?
baby needs folate to make healthy new cells, and to make DNA and RNA (genetic material). These are cell-building blocks. Folate also is essential to form normal red blood cells and certain amino acids
what are some milestones during the Fetal Period: Last 7 Months
- A period of rapid growth and refinement of
organ systems
– From 11⁄2 to 20 inches
– From 0.02 to 7.1 pounds - Fetus becomes more responsive
- Behaviour becomes increasingly regular and
integrated - Fetuses become viable between 24-26 weeks
when does a fetus begin learning
- Responding to sounds in
intrauterine environment
~6-7 months
whats Habituation?
the fetus
decreases responses to
repeated or continued
stimulation, then increases
response to new sound
do Newborn infants recognize
rhymes and stories
presented before birth?
yes, the will recognixe
- Cat in the Hat
– Mother’s voice
– Native language
what do new brons prefer
Newborns also prefer
smells and tastes that are
familiar because of
prenatal exposure
what are Teratogens
Any disease, drug, or other environmental agent
that can harm a developing embryo or fetus
What are some possible teratogens?
– Maternal diseases
– Drugs
– Environmental hazards
is it true that The same defect can be caused by different
teratogens
yes it is true
what can result from a single
teratogen
A variety of effects
what do the effects of tratogens depend on?
– Timing of exposure
– Amount and length of exposure (dose-response
relation)
– Genetic susceptibility of the fetus
what are some other hazards and explain
- Nutrition
– Severe malnutrition in the mother ⇨ babies born low
birthweight, later cognitive deficits - Stress
– Prolonged and severe emotional stress is associated with
stunted growth, prematurity, low birthweight, and
irritable infants - Age
– Prime time for childbearing: 16-35 years
