Genes and Epigenetics Flashcards

Genes, Epigenetics, and Neuroembryology

DNA

The molecule that carries genetic information in living organisms, consisting of double strands of phosphate and sugar, forming a double helix structure, joined together by pairs of bases (nucleotides).

Codon

The codon is like a “word” in the “sentence” that makes up a gene. Each codon specifies one particular amino acid.

Amino Acid

Amino acids are organic compounds that serve as the building blocks of proteins. They combine in specific sequences to form proteins, which perform a wide range of functions in organisms.

Gene Transcription

The process by which the information in a gene (segments of DNA) is copied into messenger RNA (mRNA) to be translated into a protein. This occurs in the nucleus and is a crucial step in gene expression.

Protein Synthesis: Translation

mRNA binds to ribosomes, Sequences of base pairs (codons) are read, creating amino acids (20 different kinds.) Amino acids are linked together to form peptides (small) or proteins (big.)

Peptides

Short chains of amino acids linked by peptide bonds, typically consisting of 2 to 50 amino acids. Peptides can function as hormones, neurotransmitters, or serve roles in cellular signaling.

Proteins

Large biomolecules composed of one or more long chains of amino acids, proteins perform a vast array of functions within living organisms, including catalyzing metabolic reactions, providing structural support, and regulating gene expression.

“This collection of chromosomes in the fertilized egg…

constitutes the complete set of instructions for development...”

“We know that the instructions for how the egg develops are…

written in the linear sequence of bases along the DNA of the germ cells.”

“We all recognize that in the fertilized egg there is a set of genes...and that these genes give…

instructions that ultimately produce a complex adult.”

Genes

blueprints for the assembly and regulation of proteins.

What is a program?

A sequence of instructions.

What Causes Gene Expression?

When a gene product is needed, a signal from its environment, not an emergent property of the gene itself, activates expression of that gene.

Material Basis

genes provide the instructions for producing proteins and other molecules that guide cell growth, differentiation, and the formation of tissues and organs.

Genetic “programming”

A qualitative CHANGE in gene expression over development

A sequential silencing of particular genes as cells differentiates

Sequential Silencing

The coordinated, step-by-step or time-ordered suppression of gene expression rather than shutting down all target genes simultaneously.

Totipotent Cells

Cells that have the potential to develop into any cell type in the organism, including extra-embryonic tissues.

Pluripotent Cells

Cells that can differentiate into nearly all cell types, excluding extra-embryonic tissues.

Specialized Cells

Cells that have undergone differentiation to perform specific functions within an organism. ex. neurons, astrocytes, oligodendrocytes.

Progressive Determination

As development proceeds potential outcomes become more and more constrained.

Epigenetic Information

Information outside of the genome. Epigenetic information helps cells maintain patterns of gene expression and cellular identity without changing the DNA sequence itself. Some epigenetic states can be passed on when cells divide.

Intrinsic Cues

Internal signals or factors within a cell that influence its development. Example: Cytoplasmic or nuclear proteins inherited when a cell divides.

Extrinsic Cues

External signals from the cellular environment that influence a cell’s development by binding to receptors and triggering signaling cascades that alter gene transcription. Examples: Diffusible molecules, cell membrane markers, and extracellular signals.

The “Epigenetic Landscape”

A metaphor for how genes are regulated during development

Term coined by C.H. Waddington in the 1950s

Regressive Development

The process of eliminating, reducing, or refining existing structures and connections during development.

ex. Unused or unnecessary synapses are eliminated through synaptic pruning.

• Some neurons die through programmed cell death, called apoptosis.

• Excess connections are removed to make neural circuits more efficient.

Progressive Development

The process of gaining or developing new structures, connections, and functions as an organism grows.

ex. Cells become more specialized through differentiation.

• Neurons form new connections with other neurons.

• New abilities and functions emerge as the nervous system develops.

Blastula

A hollow ball of cells formed early in embryonic development, which eventually develops into the gastrula. Prepares the embryo for the next stage of development.

Endoderm

One of the “germ layers” of the formation of the gastrula. The innermost layer of cells in the embryo that develops into the digestive system, gut, lungs, and liver.

Mesoderm

One of the “germ layers” of the formation of the gastrula. It is the middle layer of cells in the embryo that develops into muscles, cardiovascular, most bones, urogenital systems, and other organs.

Ectoderm

One of the “germ layers” of the formation of the gastrula. It is the outermost layer of cells in the embryo that develops into the skin, teeth, cranial bones, nervous system, and sensory organs.

Induction

Interaction between tissues where extrinsic information from one tissue (the organizer) modifies the development of another.

Gastrulation

Sets the stage for induction of the nervous system.

Neural Plate Induction

Neural inducers from mesoderm inhibit ectoderm from differentiating into skin, induce overlying ectoderm to differentiate into neural tissue.

Neurulation

The process during embryonic development where the neural plate folds to the neural groove, then forms the neural tube, ultimately giving rise to the central nervous system.

Neural Plate

A thickened region of ectoderm that gives rise to the neural tube during neurulation, forming the basis for the central nervous system.

Neural Groove

The indentation that forms in the neural plate during neurulation, which eventually deepens to create the neural tube.

Neural Tube

The structure that forms from the folding of the neural plate during neurulation, ultimately giving rise to the brain and spinal cord.

All parts of the CNS arise from…

the neural tube.