Download Chapter 10: Control of Gene Expression What Is Gene Control? A

Chapter 10: Control of Gene Expression
What Is Gene Control?
A typical cell in your body uses only about ____________ of its genes at one time
Some genes affect structural features and metabolic pathways and are expressed
in __________________
Others genes are expressed only by certain _____________ (e.g., globin in RBCs)
Control over __________________allows cells to respond to changes in their
environment
Gene Expression Control
Includes: __________________; ______________________________;
__________________; ________________________
The “____________” that turn a gene on or off are molecules or processes that
____________ or ____________ the individual steps of its expression
Transcription
__________________: bind directly to DNA and affect whether and how fast a
gene is transcribed
__________________: bind to __________________ or __________________ to
shut off or slow down transcription by preventing RNA polymerase from
accessing the promoter or by impeding its progress along the DNA strand
________________________bind directly to the promoter, or to a silencer
that may be thousands of base pairs away from the gene
____________: in prokaryotes, a binding site in DNA for a repressor
_______________: recruit RNA polymerase to a promoter region to enhance
transcription
____________: distant DNA binding site for eukaryotic activators
________________________affects DNA transcription: only DNA regions that
are ____________from histones are accessible to RNA polymerase
Adding __________________ (—COCH3) to a histone loosens the DNA
and ________________________
Adding __________________ (—CH3) to a histone tightens the DNA and
________________________
mRNA Processing and Transport
Delaying the ______________________________of mRNA delays translation by
preventing mRNA from reaching the cytoplasm
mRNA must first be ____________, ____________, and finished with a
__________________before leaving the nucleus
________________________can affect the form of a protein; different final
mRNA’s can be produced from the original mRNA depending on which exons are
joined together
mRNAs are delivered to organelles or specific regions of cytoplasm via “zip
codes” located near the ________________________; this allows translation of
an mRNA close to where its protein product is being used
Translation
A cap on an mRNA “zip code” sequence _____________________until mRNA
has reached its final destination, close to where the protein product is being used
mRNA stability alters translation rates and is affected by base sequence, the
______________________________, and __________________short lived
mRNA enables cells to adjust for their protein needs
In eukaryotes, translation of a particular mRNA can be shut down by tiny bits of
noncoding RNA called __________________: complementary in sequence to part
of an mRNA
___________: microRNAs bind to complementary stretches and mark that
mRNA for destruction, no translation occurs and no protein is produced
_____________________is also a factor in control over translation in prokaryotes
Bacteria can shut off translation of a particular mRNA by expressing an
____________ (complementary) RNA strand
With double-stranded RNA, ____________ cannot initiate translation
Post-Translational Modification
Many newly synthesized polypeptide chains must be ____________ before they
become functional
Example: some enzymes become active only after they have been
phosphorylated
Post-translational modifications ____________, ____________, or
____________ many molecules
How Do Genes Control Development in Animals?
Master Genes
As an animal embryo develops, its cells __________________ and form tissues, organs,
and body parts; this is driven by cascades of ______________________________
The products of ________________________the ____________of many other genes;
final outcome is the completion of an intricate task such as the formation of an eye
Orchestration of gene expression during development:
__________________are delivered to opposite ends of an _________________
____________as it forms
These mRNA’s are ____________after the egg is fertilized and the ___________
____________ diffuse away, forming ____________ that span the entire
developing embryo
The nucleus turns on __________________based on its position relative to the
________________________
__________________products also form__________________, further
influencing which additional master genes the nucleus will turn on
Eventually, the products of master genes cause __________________ cells to
__________________, and specialized structures to form
Homeotic Genes
A ________________________is a master gene that governs the formation of a
__________________- such as an eye, leg, or wing
Animal homeotic genes encode for proteins called ______________________that
contain a __________________, region of about sixty amino acids, that bind
directly to a ____________ and turn on a set of genes
Homeotic genes are often named for what happens when a ____________ alters
their function (Examples in the fruit fly: Antennapedia gene, Tinman, Wingless)
A ____________ is an experiment in which a gene is not expressed due to
deliberate__________________by the introduction of a ____________ or a
complete ____________ of the gene itself. (Results in a __________________)
What Are Some Outcomes of Gene Control in Eukaryotes?
X Marks the Spot
In humans and other mammals, a female’s cells contain two __________________
In each cell, one __________________is always tightly condensed, termed
__________________
Most of the genes on a Barr body are ____________; X chromosome inactivation
ensures that only one of the two X chromosomes in a female’s cells is active
________________________: mechanism in which X chromosome
inactivation equalizes gene expression between males and females
There is ________________________of maternal and paternal X chromosomes
in each cell
An adult female mammal is a “____________” for the expression of X
chromosome genes; some express the maternal X chromosome while
some express the paternal X chromosome
An X chromosome gene called XIST is transcribed on only one of the two X
chromosomes; the gene’s product, a long noncoding RNA, sticks to the
chromosome that expresses the gene, causing it to condense into a Barr body
Male Sex Determination in Humans
The human __________________contains the master gene for male sex
determination in mammals, ______
______ expression in ______ embryos triggers the formation of testes
which produce the sex hormone testosterone
Mutations in the SRY gene cause ______ individuals to develop external
genitalia that appear female
What Are Some Outcomes of Gene Control in Prokaryotes?
Prokaryotes do not undergo development, so these cells have no need for ____________
Prokaryotes do respond to environmental fluctuations by adjusting __________________
Example: bacteria transcribe certain genes only when a specific nutrient is
available; the cell does not waste energy producing gene products that are not
needed
Bacteria control gene expression mainly by adjusting the ________________________
Genes that are used together often occur ____________ on the chromosome and share a
single ____________that precedes genes, so all are ________________________into a
single RNA strand
____________: group of genes together with a promoter–operator DNA sequence that
controls their transcription
The lac Operon
An operon called______allows E. coli cells to metabolize lactose
The lac operon includes __________________and a ____________ flanked by
two ____________
Three genes of the lac operon:
One gene encodes a __________________that brings lactose across the
plasma membrane
Another gene encodes an __________________ that breaks the bond
between lactose’s two monosaccharide monomers, glucose, and galactose
A third gene encodes an __________________whose function is still
being investigated
When lactose is not present, a ____________ binds to the two ____________and
twists the region of DNA with the ____________ into a loop
________________________cannot bind to the twisted up promoter, so
the lac operon’s genes cannot be____________
When ____________ is present, some of it is converted to another sugar that
binds to the ____________and changes its ____________
The ________________________releases the ____________and the
looped DNA unwinds
The promoter is now accessible to ________________________, and
transcription of lactose metabolizing genes begins
Lactose Intolerance
In the majority of human worldwide, the ability to digest ____________ stops at
about age five, when expression of the gene for ____________ (enzyme produced
by intestinal cells) shuts off
When lactase production slows, lactose passes undigested into the ___________
_______, which hosts huge numbers of ____________which switch on their lac
operons, resulting in the production of gaseous products – causing distention, pain,
and diarrhea
Not everybody is lactose intolerant about ____________of human adults carry a
mutation that allows them to digest milk; this mutation is more common in some
populations than in others
Can Gene Expression Patterns Be Inherited?
Direct __________________ of DNA suppresses gene expression and once a DNA
nucleotide becomes __________________, it will usually stay methylated in all of a
________________________
Methylation is an __________________ modification: heritable changes in gene
expression that are not the result of changes in DNA sequence
Methylation is influenced by ______________________________
Example: humans conceived during a famine have an unusually low number of
methyl groups in certain genes which leads to the expression of hormones that
foster prenatal growth and development; may offer a survival advantage in a poor
nutritional environment
Methylation of __________________is normally “______” in the first cell of the new
individual, with new methyl groups being added and old ones being removed. However,
reprogramming __________________all methyl groups and these can be passed on to
____________
Example: Grandsons of boys who endured famine in 1944 Nazi-occupied
Netherlands, lived about 32 years longer than grandsons of boys who ate well
during the same winter.