Week 2 Flashcards
Define canalization
The tendency of a trait to remain stable despite how a person’s genes or environment may be reacting
A “typical” pattern of growth in a trait among most humans is an example of…
Canalization of that trait
A highly canalized trait is likely to have a lot of constraints coming from…
Genetics
Define phenotypic plasticity
The ability of a genotype to produce various phenotypes which may confer environmental adaptation
Muscle mass and fat mass are good examples of traits which are highly (canalized/plastic)
Plastic
Plasticity has its most marked effects in these stages of life
Infancy to adolescence
Why are the adult and post-reproductive life periods less plastic than other life periods?
During these periods we are not growing very much
What are 3 methods by which humans are able to adapt to their environment?
Culture and technology
Physiology and development
Genetic adaptation
Humans are most reliant on (1) to mediate environmental stresses
Culture and technology and physiology (as opposed to genetics)
What likely drove the evolution of a very flexible life cycle observed in humans?
An unpredictable environment
Periods of time which can have the most drastic impacts on human growth and development are called…
Critical windows
When is a human considered to be the most vulnerable to its environment?
The first 1000 days
What is hyperplasic growth?
A period in time where cells are growing in number (rapid division) - structure and function of cells are being established
What is hypertrophic growth?
Follows hyperplasic growth, cells increase in size
At what point is the physiology of your cells “locked in”?
In early childhood after hyperplasic growth
Why are critical developmental windows so short?
Because we want to set them up when the environment is stable, and the longer the window is the less chance there is of the environment remaining stable
How do humans ensure our babies are sheltered from a variable environment?
The baby’s nutrition is provided by the mother, who is able to buffer the environmental conditions for the baby
What “environment” is a human baby exposed to in its first 1000 days?
The mom: placenta and breastmilk
What is transient gestational diabetes?
Giving energy to a baby may increase the mom’s insulin signals - high levels of insulin may cause transient resistance while this is happening and usually goes away after birth = gestational diabetes
Why does the end of the critical window coincide with weaning?
By the time you’re weaned you are exposed to the environment, don’t want to be super sensitive to it at this point
How does a mom signal her phenotype/nutritional status to her baby in utero?
- Nutrients in the blood
- Hormones
- Cytokines and immune signals
- Metabolites (like glucose)
How is a mom able to signal stress to her baby if cortisol cannot cross the placenta?
Cortisol affects testosterone secretion (among other hormones) which are able to cross the placenta
In a study on stress and colony density, female seals who were in dense colonies tended to be (less/more) stressed than seals in less dense colonies
More - crowding = stressed
In seals, increased prenatal testosterone (due to stress) influenced these three qualities:
- Locomotor activity
- Growth
- Increased Competitiveness
Describe complimentary feeding and why it is advantageous for human babies
Complimentary feeding = Feeding a mixture of breast milk and other soft foods
Advantageous because = this allows us to have some flexibility in the age we wean our kids, we can do what’s best for the mom
Compared to other primates, humans wean their children (early/late)
Early!
Why could it be that the HPG axis on in babies in the first 6 months of life?
Could be because the mom’s hormonal axes are very much on during breastfeeding - could influence the babies HPG axis
Leptin is released from…
White adipose tissue
What is leptin’s role?
Signal to the brain the status of the body’s energy stores
How does the mom signal to the baby what her energy stores are?
Through leptin which can cross the placenta/breastmilk
If a person has more body fat, their leptin secretion will be (higher/lower)
Higher
When leptin levels are low, (1) is stimulated
Appetite
What is the role of TGF-b in infants? (2)
- Crosses the breast milk and functions as an anti-inflammatory protein and induces the production of antibodies in the infant
- Helps to mature the immune and intestinal cells of the infant
Infants who were breastfed may have more of this protein than those who were formula fed
TGF-b
Why do humans have so much HMO in their breast milk when no other mammals have this and it is indigestible to us?
It is specifically for the gut microbiome - feeds “good” bacteria in the gut
(1) colonizes the infant gut with bacteria
Breastmilk
When are the 2 times a mother transfers gut microbiome content to her offspring?
Birth and breastfeeding
What kind of bacteria specifically digests HMOs from breastmilk?
Bifidobacteria
Bifidobacteria’s main role is to..
Outcompete “bad” bacteria for space in the gut microbiome
The two main mechanisms which control access of TFs to DNA are…
DNA methylation and histones
Changes in the epigenome are heritable when these changes occur in…
Egg and sperm cell DNA
A poor maternal diet in mice may unmethylate this gene, which turns it on
The agouti gene
If a baby is born in high-altitude conditions, how is it born adapted to these conditions if the mom is buffering her environment?
Mom’s adaptation shapes the signals that the fetus receives, and the fetus is able to respond accordingly
When the critical window closes, how do many traits respond?
Respond by canalizing
High levels of cortisol impairs…
Immune function
