Lecture for Chapter 10
Expression and Regulation
Chapter 10 Outline
• 10.1 How Are Genes and Proteins Related?
• 10.2 How Is Information in a Gene Transcribed
into RNA?
• 10.3 How Is the Base Sequence of a Messenger
RNA Molecule Translated into Protein?
• 10.4 How Do Mutations in DNA Affect the
Function of Genes?
• 10.5 How Are Genes Regulated?
10.1 How Are Genes and Proteins Related?
The Link Between DNA and Protein
•
______contains the molecular blueprint
of every cell
• ________the “molecular workers” of the cell
• ___________ control cell shape,
function, reproduction, and synthesis of
biomolecules
• The information in DNA _______ must
therefore be linked to the _______ that
run the cell
One Gene Encodes One Protein
• Synthesis of new molecules inside the cell
occurs through _____________________
• Each step in a biochemical pathway is
catalyzed by a _________________
One Gene Encodes One Protein
• George Beadle and Edward Tatum
showed that _____________ encodes the
information for ____________________ in
a biochemical pathway
• There are exceptions to the one gene/one
protein relationship, as discussed later
RNA Intermediaries
• DNA in eukaryotes is kept in the _________
• Protein synthesis occurs at__________ in
the cytoplasm
• DNA information must be carried by an
____________________ from nucleus to
cytoplasm
RNA Intermediaries
• RNA differs
structurally from DNA
– RNA is ______
_________
– RNA uses the sugar
___________
– RNA uses the
nitrogenous base
____________
instead of thymine (T)
RNA Intermediaries
• There are three types of RNA involved
in protein synthesis
– __________________
– __________________
– __________________
RNA Intermediaries
• There are three types of RNA involved in
protein synthesis
– Messenger RNA (mRNA) _______ DNA
gene ____________________________
RNA Intermediaries
– Transfer RNA (tRNA) brings _______
______________ to the ribosome
RNA Intermediaries
– Ribosomal RNA (rRNA) is part of the
structure of ________________
Transcription and Translation
•
DNA directs protein
synthesis in a two-step
process
1. Information in a DNA
gene is copied into
mRNA in the process of
_______________
2. mRNA, together with
tRNA, amino acids, and
a ribosome, synthesize
a protein in the process
of ____________
The Genetic Code
• The base sequence in a DNA gene
dictates the _______________ of amino
acids in translation
• Bases in mRNA are read by the ribosome
in _________ called ____________
• Each codon specifies a ________ amino
acid in the genetic code
• Each mRNA also has a _________ and a
____________________________
10.2 How Is Information in a Gene
Transcribed into RNA?
• Transcription of a DNA gene into
RNA has three stages
– ____________
– ____________
– ____________
Initiation
1. DNA molecule is _________ and strands are
_________ at the beginning of the gene
sequence
2. ______________ binds to _________region
at beginning of a gene on _______________
Elongation
Elongation phase of transcription
1. RNA polymerase synthesizes a
sequence of _________________ along
DNA template strand
2. Bases in newly synthesized RNA strand
are __________________________
strand
3. RNA strand peels away from DNA
template strand as DNA strands repair
and wind up
Elongation
•
As elongation proceeds, one end of the ____
drifts away from the DNA; RNA polymerase
keeps the other end temporarily attached to
the DNA ______________strand
Termination
Termination phase of
transcription
– RNA polymerase
reaches a
________
_____________
and releases
completed ____
_________
10.3 How Is the Base Sequence of a
Messenger RNA Molecule Translated into
Protein?
mRNA
• An intermediate molecule is required to
convey DNA gene sequence to the
ribosome
• Messenger RNA (mRNA) performs this
function by serving as the __________
________________________ that is
read by a ribosome
mRNA
• In prokaryotes
– The chromosomes _________ contained
within a nucleus
– _____________________ in a gene encode
for the amino acids of ___ protein
mRNA
…In prokaryotes
– Genes for a related
function are
_______ and are
transcribed _______
– Transcription and
translation occur
______________
within the same
compartment
mRNA
• In eukaryotes
– The DNA is in the _______ and the
ribosomes are in the _____________
– The genes that encode the proteins for a
biochemical pathway are ____________
together on the same chromosome
mRNA
• In eukaryotes (continued)
– Each gene consists of multiple segments
of DNA that encode for protein, called
___________(expressed)
– Exons are interrupted by other segments
that are not translated, called _______
(in-between)
mRNA in eukaryotes (continued)
•
•
•
Transcription of a gene
produces a very ________
strand that contains
introns and exons
Enzymes in the nucleus
_____________ and
splice together the ______
to make _____ mRNA
mRNA exits the nucleus
through a membrane ___
and associates with a
_________
mRNA
•
Why are eukaryotic
genes split up into
exons and introns?
– Through “alternate”
splicing, a cell can
make ________
_______________
______________
– *Exception to the
one gene/one
protein relationship
Ribosomes
•
Ribosomes are large complexes of
___________________
Ribosomes
•
Ribosomes are composed of two subunits
– __________ has binding sites for _____ and a
______
– Large subunit has binding sites for two_____
molecules and ___________ site for peptide
bond formation
Transfer RNAs
•
•
Transfer RNAs hook up to
and bring _______________
_______________
There is ______________ of
tRNA assigned to carry each
of the twenty different amino
acids
Transfer RNAs
•
•
Each tRNA has three
exposed bases called an
______________
The bases of the tRNA
anticodon ______ with an
______________ within a
ribosome binding site
Translation
Ribosomes, tRNA, and
mRNA cooperate in
protein synthesis, which
begins with __________
1. The mRNA binds to the
_____________ subunit
2. The mRNA slides through
the subunit until the first
____ (start codon) is
exposed in the first _____
binding site…
Translation-Initiation
3. The first tRNA carrying
methionine (and
anticodon ____) binds to
the mRNA start codon
completing the ______
_________________
4. The large ribosomal
subunit _________
______________
Translation- Elongation
Middle phase of protein
synthesis: Elongation
1. A second tRNA binds
to the second tRNA
binding site adjacent to
the first tRNA
2. The
________________
__________________
__________________
_______ codon
exposed in the second
tRNA binding site…
Translation – …Elongation…
3. A _____________
forms between the
methionine and
second amino acid
through the action of
the ribosome
____________
4. The first amino acid
is ______________
________ in the first
tRNA binding site…
Translation…Elongation
5. The “empty” tRNA in
the first binding site
leaves the ribosome
6. The ____________
down the mRNA by
_______________,
transferring the tRNA
holding the amino
acid chain to the first
tRNA binding site…
Translation
7. A new tRNA with
anticodon
complementary to the
newly exposed codon
in the second tRNA
binding site
approaches and the
whole elongation
cycle repeats
8. Empty tRNAs are
_________ with their
appropriate amino
acids by enzymes in
the cytoplasm
End phase of protein synthesis:
Termination
1. A __________ on
the mRNA slides
into the second
tRNA binding site
2. A special _______
binds to the stop
codon
3. The ribosome
breaks into
separate ______…
Translation… Termination
4. The finished
_____________
is released
5. The mRNA is
released and
can be used to
make another
protein
Recap
• Each DNA gene
codes for ______
_________
• Transcription
produces an
mRNA strand
_______________
_____ gene
template strand
Recap
• The mRNA strand
associates with a
___________
• Transfer RNAs in
the cytoplasm are
loaded with their
appropriate amino
acids by
cytoplasmic
_____________
Recap
• The ribosome “selects”
the tRNAs based on the
base pairing of the
____________with the
exposed mRNA
_________
• The mRNA contains
_____________ signals
to define where protein
synthesis begins and
ends
Effects of Mutations on Proteins
• Recall that mutations are changes in the
base sequence of DNA
• Most mutations are categorized as
– _______________
– _______________
– _______________
– _______________
– _______________
Effects of Mutations on Proteins
•
Inversions and translocations
– When pieces of DNA are ________________
____________________________ or location
– Not problematic if entire gene is moved
– If gene is split in two it will no longer code for a
complete, functional protein
Effects of Mutations on Proteins
• Insertions or deletions
– ________________ are added or
subtracted from a gene
– _______________ of RNA codons is
changed
• THEDOGSAWTHECAT is changed by deletion
of the letter “S” to THEDOGAWTHECAT
– Resultant protein has very different amino
acid sequence; almost always is _____
________________
Effects of Mutations on Proteins
• Nucleotide substitutions (point mutations)
– An __________________ takes the place of
a correct one
– Protein structure and function is __________
because many amino acids are encoded by
multiple codons
– Protein may have amino acid changes that
are unimportant to function _________
________________
Effects of Mutations on Proteins
• Effects of nucleotide substitutions
– Protein function is __________ by an altered
amino acid sequence (as in gly val in
hemoglobin in sickle cell anemia)
– Protein function is destroyed because DNA
mutation creates a premature __________
Mutations Fuel Evolution
• Mutations are ________________________
• Approx. 1 in 105-106 eggs or sperm carry a
mutation
• Most mutations are _________________
Mutations Fuel Evolution
• Mutations create ________________ and
are the ultimate source of ______________
• Mutant gene sequences that are beneficial
may spread through a population and
become common
How Are Genes Regulated?
• The human genome contains ________
____________
• A given cell “expresses” (transcribes) only a
small number of genes
• Some genes are expressed in all cells
• Other genes are expressed only
– In certain _________ of cells
– At certain _________ in an organism’s life
– Under specific _______________ conditions
Gene Regulation in Prokaryotes
• Prokaryotic DNA is organized into units
called ___________, which contain
functionally related genes
Gene Regulation in Prokaryotes
• Each operon consists of
– A ____________ gene, which controls the
transcription of other genes
– A _______________, which RNA polymerase
recognizes as the place to start transcribing
– An ____________, which governs access of
RNA polymerase to the promoter
– The ___________________, which encode for
related proteins
Gene Regulation in Prokaryotes
• Whole operons are regulated as ______,
so that functionally related proteins are
synthesized simultaneously when the need
arises
Gene Regulation in Prokaryotes
• The intestinal bacterium Escherichia coli
_______ lives on what its host eats
• Specific ________ are needed to metabolize
the type of food that comes along
• e.g. in newborn mammals, E.coli are bathed in
milk, containing the milk sugar ___________
• The lactose _______ contains three structural
genes, each coding for an enzyme that aids in
lactose metabolism
Gene Regulation in Eukaryotes
•
Eukaryotic gene regulation
–
–
–
–
DNA is in a __________________________
Variety of cell types in multicelluar eukaryotes
The genome is organized differently
RNA transcripts undergo complex _________
Gene Regulation in Eukaryotes
•
Expression of genetic information by a
eukaryotic cell is a multistep process,
beginning with _______________, and
ending with a protein that performs a
particular function
Gene Regulation in Eukaryotes
Gene expression is
regulated in a number of
ways
– The ___________________
of a gene can be controlled
– Different mRNAs may be
_______________________
– Proteins may be synthesized
in an __________ and require
modification for activation
– _____________ of a protein
can be regulated
Gene Regulation in Eukaryotes
•
In eukaryotic cells, transcriptional
regulation occurs on at least three levels
– The _________________
– ___________ of chromosomes
– __________ chromosomes
Gene Regulation in Eukaryotes
•
Regulatory proteins can bind to a gene’s
__________ region and alter transcription
– The protein hormone estrogen causes binding
of a protein to certain gene promoters,
activating transcription
Gene Regulation in Eukaryotes
•
•
Condensed or tightly wound DNA can
make genes inaccessible to ____
________________
Whole chromosomes can be ___________
and inactivated (e.g. _____ bodies in
female mammals)
Gene Regulation in Eukaryotes
• The X chromosome in cats carries fur color
genes
• Female cat cells inactivate one of two X
chromosomes in every cell (producing a
__________)
– Different patches of skin cells in a cat inactivate
_______________________
– Patches of fur growing from skin cells may differ
in color if fur genes on X chromosomes differ
Gene Regulation in Eukaryotes
• Patches of different colored fur only occur in
____________ (e.g. calico cats)