Gene Expression Flashcards
(33 cards)
Changes to the chemical groups that associate with DNA profoundly affect which parts of the genome are accessible to transcription factors and under which conditions. Such changes to the molecules that bind to DNA that are transmitted to daughter cells when the cell divides are termed _________literally, “__________.”
epigenetic
outside the gene
Specific classes of ______ and ______ molecules carry out epigenetic changes, and much of the genome encodes these modifiers of gene expression.
proteins and RNA
do not alter the DNA base sequence, although they are passed from one cell generation to the next.
Epigenetic changes
A more complete portrait of gene expression emerges through_______, which considers all proteins made in a cell, tissue, gland, organ, or entire body
proteomics
_______patterns change over time and in different cell types.
Gene expression
The subunit composition of_____\ changes in the embryo, fetus, and after birth.
hemoglobin
As a pancreas forms, ________ diverge from shared stem cells and their daughters specialize.
progenitor cells
tracks all of the proteins in a cell, tissue, organ, or organism under specific conditions.
Proteomics
Much of the control of gene expression occurs in two general processes.
chromatin remodeling
microRNAs, bind the 3′ ends of certain mRNAs, preventing their translation into protein
_____, interactions of the histone proteins associated with DNA with other chemical groups expose some sections of DNA to transcription factors and shield other sections, blocking their expression.
chromatin remodeling
______, bind the 3′ ends of certain mRNAs, preventing their translation into protein.
microRNAs
play a major role in exposing DNA when and where it is to be transcribed, and shielding it when it is to be silenced.
Histones
enzymes add or delete small organic chemical groups to histones in a process called
chromatin remodeling
adds or removes certain organic chemical groups to or from histones. The pattern of binding controls whether the DNA wrapped around the histones is transcribed or not.
Chromatin remodeling
The three major types of small molecules that bind to histones are
acetyl groups, methyl groups, and phosphate groups
The key to the role histones play in controlling gene expression lies in_________. They bind to very specific sites on certain histones, particularly to the amino acid lysine.
acetyl groups (CH3 CO2 )
a group of proteins called an_______ attracts the enzyme (acetylase) that adds acetyl groups to specific lysines on specific histones.
enhanceosome
Adding______ groups to these lysines neutralizes their positive charge.
Because DNA carries a negative charge, this change moves the histones away from the DNA, enabling transcription factors to enter, bind, and begin transcription.
acetyl
Enzymes called______ remove acetyl groups, which shuts off gene expression.
deacetylases
are also added to or taken away from histones. When it binds to a specific amino acid in a specific histone type, a protein is attracted that shuts the DNA off.
Methyl groups (CH3 )
As ______are added, methylation spreads from the tail of one histone to the adjacent histone, propagating the gene silencing.
CH 3groups
Methyl groups also control gene expression by binding to______ at about 10,000 places in the genome.
cytosines
These changes in gene expression are heritable from cell generation to cell generation, but they do not alter the DNA base sequence—that is, they are_______.
epigenetic
Addition and removal of acetyl groups, methyl groups, or phosphate groups are examples of
epigenetic changes
