WGSS 1105 Chapter Notes - Chapter 11: Pancreatic Islets, Fetal Hemoglobin, Yolk Sac
23 Jan 2017
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11: Gene Expression and Epigenetics
● Changes to the molecules that bind to DNA that are transmitted to daughter cells
when the cell divides are termed epigenetic (outside the gene)
○ Epigenetic changes do not alter the DNA base sequence and are
reversible
○ Passed from one cell generation to the next
○ Changes may affect the next generation of individuals if the conditions to
which a fetus is exposed become dangerous
Globin Chain Switching
● Globin proteins transport oxygen in the blood
● Vividly illustrate control of gene expression because in a process called globin
chain switching they assemble into different hemoglobin molecules depending
upon stage of development
● Beta - 146 amino acids long , alpha - 141 amino acids long
● Chemical basis is the different globin polypeptide chains attract oxygen
molecules to different degrees
● Embryo develops into the fetus → epsilon and zeta globin polypeptide chains
decrease in number, as gamma and alpha chains accumulate
● Hemoglobin = two gamma and two alpha chains = fetal hemoglobin
● Globin chain are manufactured
○ Yolk sac in embryo
○ Liver and spleen in fetus
○ Bone marrow after birth
● Pancreas is a dual gland with two types of cell clusters, exocrine part releases
digestive enzymes into ducts, whereas the endocrine part secretes polypeptide
hormones that control nutrient use directly into the bloodstream
○ Endocrine cell clusters are called pancreatic islets
Proteomics
● Proteomics - an area of genetics that identifies and analyzes all the proteins
made in a cell, tissue, gland, organ, or body
● Transcription factors are more abundant before birth because of the extensive
cell differentiation of this period, as organs form
● “Ome” words = specific function (ex: lipodome)
11.2 Control of Gene Expression
● Variations in the promoter sequence of a gene can affect how quickly the
encoded protein is synthesized
● Control of gene expresion
○ Chromatin remodeling - the histone proteins associated with DNA
interact with other chemical groups in ways that expose some sections of
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Document Summary
Changes to the molecules that bind to dna that are transmitted to daughter cells when the cell divides are termed epigenetic (outside the gene) Epigenetic changes do not alter the dna base sequence and are reversible. Passed from one cell generation to the next. Changes may affect the next generation of individuals if the conditions to which a fetus is exposed become dangerous. Globin proteins transport oxygen in the blood. Vividly illustrate control of gene expression because in a process called globin chain switching they assemble into different hemoglobin molecules depending upon stage of development. Beta - 146 amino acids long , alpha - 141 amino acids long. Chemical basis is the different globin polypeptide chains attract oxygen molecules to different degrees. Embryo develops into the fetus epsilon and zeta globin polypeptide chains decrease in number, as gamma and alpha chains accumulate. Hemoglobin = two gamma and two alpha chains = fetal hemoglobin.
