HSCI 216 Lecture Notes - Lecture 8: Vasoconstriction, Low Birth Weight, Chronic Kidney Disease

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HSCI 216
Day 8
July 6, 17
Growth and Development Pregnancy
Learning Objectives
- To describe how environment affects development
- To describe how the mother is the baby’s first environment
- To describe intragenomic conflicts and maternal-offspring conflicts
- To identify potential times for conflict between mother and offspring
The external environment directly influences the internal environment
- Unconstrained
o Environment is supportive
o Growth achieve genetic potential
- Patterned/Channelled
o Growth shaped by environmental pressures
o To achieve better adaptation (developmental adaptation)
o Ex: children who grow up in higher altitudes are better adapted than parents who
acclimatated to high attitudes as adults
- Constrained
o Growth is constrained (not reach full potential), impact depends on timing and
severity of insults
What constitutes the baby’s first environment?
- What a mother eats etc.
Mothers as environment
- The relationship between mothers and their unborn offspring is a complex one
- This relationship is marked by 2 very important things
o Constraints in the quality of environment the mother faces which then translates
into the quality of the fetus’ environment
o Conflicts of interest between mother and fetus
External constraints Internal effects
Plasticity itself is hypothesized to be an evolved trait
Constrained environment (mom)
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fetus will attempt to adapt to pressures of environment
Survival depends on nature and intensity of constraints
in certain cases (ex: intrauterine growth restriction IUGR) survival is possible, BUT
COMES AT A COST
** pre-natal constraints tend to affect post natal phenotypes **
- The resulting phenotypes represent:
1. The unavoidable results of prenatal constraints
a. Ex: small phenotype due to scarce energetic resources; no benefits associated
2. The costs of prenatal adaptions to those prenatal challenges
a. Scarce energetic resources
b. Adaption: fetus changes its development trajectory in utero to survive
c. Cost: lower quality post-natal phenotype
d. Ex: Fetus will prioritize neural development may result in increased risk for
metabolic syndrome (increase in cardiovascular disease, increase BP and
increase of stroke)
3. “Predictive Adaptive Responses”
a. phenotypic changes that don’t provide an immediate advantage but could aid
the individual in dealing with predictive post-natal challenges
b. Ex: Thrifty phenotype hypothesis
When phenotypic changes help a fetus survive prenatal challenges or, a child, post-natal
constrains those changes are called developmental adaptions and are said to be the result of
developmental plasticity
- Daphnia helmets “water fleas” (planktonic crustaceans)
Constraints can lead to conflicts
- Mother and fetus want to respond to that constraints differently
- Dad is involved in this conflict too
- There can even be intragenomic conflicts!
The role of intragenomic conflict in development
Intra-genomic conflict hypothesis
- Predicts that individual genes within a genome which are either not transmitted by the
same rules (e.g., “meiotic drive” or, having different parental origin, present different
replication strategies can enter in conflict with each other affecting the resulting
phenotype
- Meiotic drive = segregation distortion during meiosis: some alleles that are over
represented in oscytes
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- Phenotypes = genotype + environment
Intragenomic conflict and maternal-offspring conflict
What are the parties involved, and how do they maximize their inclusive fitness?
o Maternal Genes
o Genes in fetus/child
o Paternal genes
- Genes maximize inclusive fitness
- Maternal genes maximize inclusive fitness (I.F) of mother
o Investment depends on quality of offspring
o Sensitive to tradeoffs
Quantity vs. quality of offspring
Current vs. future reproduction
- Fetus/child
o Selected to take more form mother than she is selected to provide, up to a point
that cost to siblings becomes too great
- Paternal genes
o Survive at (almost) all costs
o Take as much from mom as possible (despite cost to siblings)
Can a species’ mating system affect maternal fetal conflict?
- The concept of the genome-imprinting conflict
Lower genetic relatedness of a male to a female’s broad (history of multiple paternity)
Selection for males to silence genes (in genetogenesis) that reduce demands on mother
Demand supressing genes maternally expressed
Higher investment by females in offspring
Selection for females to silence genes (gametogenesis) that increase demands on mother
Demand increasing genes are paternally expressed
What is our mating system? How monogamous are homo sapiens?
In “biologese”, serial monogamy = polygamy
In terms of the selective pressures leading to evolution:
Homo sapiens is a species with a moderate degree of polygamy
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Document Summary

To describe how the mother is the baby"s first environment. To describe intragenomic conflicts and maternal-offspring conflicts. To identify potential times for conflict between mother and offspring. The external environment directly influences the internal environment. Unconstrained: environment is supportive, growth achieve genetic potential. Patterned/channelled: growth shaped by environmental pressures, to achieve better adaptation (developmental adaptation, ex: children who grow up in higher altitudes are better adapted than parents who acclimatated to high attitudes as adults. Constrained: growth is constrained (not reach full potential), impact depends on timing and severity of insults. The relationship between mothers and their unborn offspring is a complex one. This relationship is marked by 2 very important things: constraints in the quality of environment the mother faces which then translates into the quality of the fetus" environment, conflicts of interest between mother and fetus. Plasticity itself is hypothesized to be an evolved trait. Constrained environment (mom) fetus will attempt to adapt to pressures of environment.

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