Page 26 - 2024-bfw-MyersAP4e-TE

Epigenetics: Triggers That Switch Genes On and Off
TEACH 1.1-4
Dig Deeper
The authors reference DNA in their
discussion of epigenetics. Under-
standing epigenetics is important
®
for the AP exam. However, specific
information about DNA is beyond the
®
scope of the AP exam.
TEACH 1.1-4
Active Learning
(15 minutes) Ask students in pairs or
small groups to discuss Figure 1.1-3
so that they have a solid understand-
ing of it. Then give them a copy of
the figure with the descriptions on the
right side left blank (that is, remove
“drugs,” “toxins,” “nutrition,” “stress,”
etc.). Ask students to fill in the
description for each developmental
stage. This activity will reveal gaps in
their understanding.
Bonus: This would be a great time to
remind students of the importance
of metacognition—learning what you
don’t know is the first step in knowing
what to study.
Distributed by Bedford, Freeman
Copyright ©
03_myersAPpsychology4e_28116_ch01_002_163.indd
16 Unit 1 Biological Bases of Behavior
03_HammerTE4e_47547_ch01_2a_163_4pp.indd 16
Recall that genes can be either active (expressed, as the hot water activates a tea bag)
or inactive. Epigenetics studies the molecular mechanisms by which environments
Genes can trigger or block genetic expression. Genes are self-
Figure 1.1-3 regulating. Rather than acting as blueprints that lead to
Epigenetic expression the same result no matter what the context, genes react.
Beginning in the womb, life An African butterfly that is green in summer turns brown
experiences lay down epigenetic
marks — often organic methyl in fall, thanks to a temperature-controlled genetic switch.
The same genes that produce green in one situation pro-
molecules — that can influence the duce brown in another.
expression of any gene in the DNA
segment they affect. (Research Prenatal Drugs, toxins, Our experiences create epigenetic marks, which are
from Champagne, 2010.)
nutrition, stress
often organic methyl molecules attached to part of a DNA
strand (Figure 1.1-3). If a mark instructs the cell to ignore
Postnatal Neglect, abuse, any gene present in that DNA segment, those genes will
variations in care be “turned off” — they will prevent the DNA from pro-
ducing the proteins normally coded by that gene. As one
AP Science Practice Juvenile Social contact, geneticist explained, “Things written in pen you can’t
®
Research environmental change. That’s DNA. But things written in pencil you can.
complexity
That’s epigenetics” (Reed, 2012).
The environmental factors men- Environmental factors such as diet, drugs, and stress
tioned here — diet, drugs, and
stress — could be variables in an Adult Cognitive can affect the epigenetic molecules that regulate gene
epigenetic study. If the research
expression. Mother rats normally lick their infants. In
challenges,
manipulates the amount of stress exercise, nutrition experiments, infant rats deprived of this licking had more
the rats experience, it would be
the independent variable. epigenetic molecules blocking access to their brain’s
“on” switch for developing stress hormone receptors.
When stressed, animals that had above-average levels
of free-floating stress hormones displayed more stress
(Champagne et al., 2003; Champagne & Mashoodh, 2009).
Epigenetics provides a possible mechanism by which
epigenetics “above” or “in Gene expression affected the effects of childhood trauma, poverty, or malnutrition
addition to” (epi) genetics;
by epigenetic molecules
the study of the molecular Worth Publishers.
may last a lifetime (Neves et al., 2019). Such experiences
may leave fingerprints in a person’s
mechanisms by which
in-depth report on the devastating & Worth Publishers. Not for redistribution.
environments can influence
genetic expression (without a genome. Some epigenetic changes may
even get passed down to future gener-
DNA change). ations. Holocaust survivors and former
Bedford, Freeman &
prisoners of war have shared epigenetic
alterations with their offspring (Costa
et al., 2018; Yehuda et al., 2016). Such
findings have led some evolutionary
occurs not only through gene trans-
Lasting effects Canadian biologists to theorize that inheritance
Senator Murray Sinclair received a mission, but also through environmen-
humanitarian award from the Canadian
Psychological Association for an Adrian Wyld/The Canadian Press/AP Photo tal influences (Uller & Laland, 2019).
2018; Ryan & Kuzawa, 2020). Stay 15/12/23 9:21 AM
Evolution, they argue, shapes human
effects of Canada’s long-running
culture and experience, which influence
residential school program that
evolution. Other scientists dispute the
removed Indigenous children from their
idea that children can inherit their par-
families. Psychologist Susan Pinker
ents’ epigenetic changes (Horsthemke,
(2015) observed that the epigenetic
effects of forced family separation “can
play out, not only in the survivors of
tuned: This scientific story is still being
residential schools but in subsequent
written.
generations.”
16 Unit 1 Biological Bases of Behavior
16
07/02/24 5:17 PM