Agriculture Reference
In-Depth Information
since antiquity. With Mendel
'
s discoveries, Darwin
'
s natural selection theories
became armed with the concept of genotype.
How a genotype is inherited, selected, and how this results in a phenotype
have become a spirited debate that has ultimately led to our ideas of genetics
and epigenetics. The concept of genetic memory that arose from developmen-
tal biology has underpinned the desire to understand the molecular basis of
epigenetics. This has
finally led to uncovering of many of the molecular
building blocks and regulatory pathways of epigenetics. The possibility that
the environment through epigenetic regulation may direct trait inheritance has
even begun to question some of our fundamental paradigms of the function of
the environment in shaping evolution. Some direct role of the environment in
heritable phenotype variation cannot be ruled out now. This has blurred our
concepts of transgenerational and developmental genetics so much that under-
standing the connections between these processes has taken an enormously
important status in biology. The pace of growth of our knowledge of the
biochemical participants in the epigenetic informational system has been truly
impressive. Major epigenetic marks involve covalent chemical modi
cations
to DNA and to histones. How these modi
cations and noncoding RNAs
are organized into an epigenetic informational system is being intensively
investigated.
Understanding the way in which the environment controls the connections
and use of epigenetic marks with the DNA sequence code promises to expose a
rich new world of biology and new toolboxes that will afford stunning new
capabilities in agriculture, medicine, and all practical applications of biology.
This chapter discusses the sea change in our understanding of genome
-
environment interactions.
KEYWORDS:
biodiversity; epimarks; genetics; ontogeny; signaling
I. INTRODUCTION
II. HISTORICAL PERSPECTIVE AND CONCEPTUAL FRAMEWORK
A. The Distribution of Natural Biodiversity
B. Genotypes and Phenotypes
C. Gene Expression and Phenotype: The Mystery of Genetic Memory
D. The Rebirth of Epigenetics
III. EPIGENETICS
A. Epigenetics: The Softer Side of Genetics
B. The Role of the Environment in Evolution
C. Transgenerational Epigenetics
D. Growth Is a Common Phenotypic Link Between Plant and Animal Epigenetics
E. The Relationship of Genetics with Epigenetics: Resetting During Development
F. Epigenetic Control of Development and Evolution
IV. EPIGENETIC MEMORY
A. Alternation of Generations
B. Ontogenic Programs
