Gene Action: 10 From DNA to Protein Flashcards
e “words” of the language of genes are three-base mRNA units called______. A particular codon specifies the same______
codons
amino acid
—used to treat people with diabetes.
insulin
preserves genetic information by giving new cells complete sets of operating instructions.
DNA replication
A protein consists of one or more long chains of amino acids called
polypeptides
A short sequence of amino acids is called a
peptide
e bonds that join amino acids are called
peptide bonds
Proteins have a great variety of functions (table 10.1).
They transport iron in the blood; provide immunity;
digest food;
clot blood;
regulate use of glucose;
forms skin, hair, and muscle; and enable cells to move
To use the genetic information in the nucleus to synthesize proteins, the process of_______ first makes a copy of a gene that is an RNA molecule complementary to one strand of the DNA double helix.
The RNA copy is taken out of the nucleus and into the______.
There, the process of_______ uses the information in the RNA to manufacture a protein by aligning and joining specified amino acids.
Finally, the protein must fold into a specific three-dimensional form in order to function.
transcription
cytoplasm
translation
Cells replicate their DNA only during____ phase of the cell cycle.
S
transcription and translation occur continuously, except during___ phase.
M
Watson and Crick, shortly after publishing their structure of DNA in 1953, described the relationship between nucleic acids and proteins as a directional flow of information called the ______
central dogma
is the bridge between gene and protein.
RNA
The bases of an RNA sequence are complementary to those of one strand of the double helix, which is called the
template strand
Complementary to RNA
Template strand
, assists the construction of an RNA molecule
RNA polymerase
Some of the information stored in DNA is copied to RNA (____), some of which is used to assemble amino acids into proteins (_____). DNA replication perpetuates genetic information.
transcription
translation
is complementary to the DNA template strand.
This is the same sequence as the DNA coding strand, with uracil (U) in place of thymine (T).
RNA sequence
The other strand of the DNA double helix is called the
coding strand
____is usually single-stranded, whereas____ is double-stranded.
Also, RNA has the pyrimidine base_____ where DNA has_——.
RNA/ DNA
uracil/ thymine
______stores genetic information
whereas_____ controls how that information is used.
DNA
RNA
The presence of the —_____at the 5′ position of ribose makes RNA much less stable than DNA, which is critical in its function as a shortlived carrier of genetic information.
OH
Encodes amino acid sequence
mRNA
rRNA
Associates with proteins to form ribosomes, which structurally support and catalyze protein synthesis
Transports specific amino acids to the ribosome for protein synthesis
tRNA
e three major types of RNA are messenger RNA, ribosomal RNA, and transfer RNA
RMT
carries the information that specifies a particular protein.
Each three mRNA bases in a row form a genetic____ word, or____, that specifies a certain amino acid
Messenger RNA (mRNA)
code/codon
Differentiated cells can carry out specialized functions because they express certain subsets of genes—that is, they produce certain mRNA molecules, also called______.
transcripts
The information in the__ is then used to manufacture the encoded proteins
transcripts
The information in the ___ is then used to manufacture the encoded proteins.
transcripts
A muscle cell, for example, has many mRNAs that specify the contractile proteins____ and ______, whereas a skin cell contains many mRNAs that specify the scaly keratin proteins
actin and myosin
associate with certain proteins to form a ribosome.
Ribosomal RNAs
is an organelle made up of many different protein and RNA subunits.
ribosome
functions as a machine to attach amino acids to form proteins
ribosome
A ribosome has two subunits that are separate in the cytoplasm but join at the __________of protein synthesis.
The larger ribosomal subunit has____ types of rRNA molecules, and the small subunit has____.
site of initiation
three
one
A ribosome from a______ cell has two subunits; together, they consist of 82 proteins and four rRNA molecules.
eukaryotic
Certain rRNAs catalyze the formation of the peptide bonds between amino acids. Such an RNA with enzymatic function is called a_____.
ribozyme
binds an mRNA codon at one end and a specific amino acid at the other.
transfer RNA (tRNA)
Some of its bases form weak chemical bonds with each other, folding the tRNA into loops in a characteristic_____
cloverleaf shape
One loop of the tRNA has three bases in a row that form the______, which is complementary to an mRNA codon.
The end of the tRNA opposite the anticodon strongly bonds to a specific_____
anticodon
amino acid
a tRNA with the anticodon sequence GAA always picks up the amino acid________.
phenylalanine
tRNA with a particular anticodon sequence always binds the same type of_______
amino acid
In more complex organisms, different cell types express different subsets of genes. To manage this, groups of proteins called_______ come together, forming an apparatus that binds DNA at certain sequences and initiates transcription at specific sites on chromosomes.
transcription factors
activated by signals from outside the cell such as hormones and growth factors, set the stage for transcription by forming a pocket for RNA polymerase—the enzyme that builds an RNA chain.
The transcription factors
Transcription factors include regions called______ that guide them to the genes they control.
binding domains
Transcription and translation are each described in three steps:
initiation, elongation, and termination.
How do transcription factors and RNA polymerase (RNAP) “know” where to bind to DNA to begin transcribing a specific gene?
In transcription initiation, transcription factors and RNA polymerase are attracted to a______, which is a special sequence that signals the start of the gene.
promoter
The first transcription factor to bind, called a______, is chemically attracted to a DNA sequence called a TATA box—the base sequence TATA surrounded by long stretches of G and C.
TATA binding protein
In the next stage,_______, enzymes unwind the DNA double helix locally, and free RNA nucleotides bond with exposed complementary bases on the DNA template strand
transcription elongation
A _________in the DNA indicates where the gene’s RNA-encoding region ends. When this spot is reached, the third stage, transcription termination, occurs
terminator sequence
____is the control point that determines which genes are transcribed. RNA nucleotides are added during_____. A______ in the gene signals the end of transcription.
Initiation
elongation
terminator sequence
RNA is typically transcribed using only a gene’s_____ strand. However, different genes on the same chromosome may be transcribed from different strands of the double helix. The coding strand of the DNA is so-called because its sequence is identical to that of the___, except with thymine (T) in place of uracil (U).
template
RNA
Since______ is short-lived, with about half of it degraded every 10 minutes, a cell must constantly transcribe certain genes to maintain supplies of essential proteins.
mRNA
For example, a DNA template strand that has the sequence
CCTAGCTAC
is transcribed into RNA with the sequence
and the coding DNA sequence is
G G A U C G A U G
G G A T C G A T G
In______, RNA is translated into protein as soon as it is transcribed from DNA because a nucleus does not physically separate the two processes.
In_________, mRNA must first exit the nucleus to enter the cytoplasm, where ribosomes are located. Messenger RNA is altered before it is translated in these more complex cells. The modifications take several steps.
bacteria
eukaryotic cells
after mRNA is transcribed, a short sequence of modified nucleotides, called a______, is added to the 5′ end of the molecule. The _____ consists of a backwardly inserted guanine (G), which attracts an enzyme that adds methyl groups (CH3 ) to the G and one or two adjacent nucleotides. This methylated _____ is a recognition site for protein synthesis.
cap
At the 3′ end, a special polymerase adds about 200 adenines, forming a “_______.” This is necessary for protein synthesis to begin, and may also stabilize the mRNA so that it stays intact longer.
poly A tail
Parts of mRNAs called_______ (short for “intervening sequences”) that were transcribed are removed.
The ends of the remaining molecule are_____ together before the mRNA is translated.
The parts of mRNA that remain and are translated are called____
introns
spliced
exons
Prior to intron removal, the mRNA is called
pre-mRNA
Introns control their own removal. They associate with certain proteins to form_________. Four _____ form a structure called a______ that cuts introns out and attaches exons to form the mature mRNA that exits the nucleus. The introns cut themselves out of the RNA.
small nuclear ribonucleoproteins (snRNPs), or “snurps
spliceosome
At first, some geneticists called introns “_______”—a term that has unfortunately persisted even as researchers have discovered the functions of many introns.
junk DNA
the mechanism of combining exons in different ways is called ________. It may explain how cell types use the same protein in slightly different ways in different tissues.
For example, a protein that transports fats is shorter in the small intestine, where it carries dietary fats, than it is in the liver, where it carries fats made in the body.
alternate splicing
is single-stranded, has uracil and ribose, and has different functions than DNA.
RNA
transmits information to build proteins.
Each three bases in a row form a codon that specifies a particular amino acid.
Messenger RNA
(2) form ribosomes, which physically support protein synthesis and help catalyze bonding between amino acids.
Ribosomal RNA and proteins
connect mRNA codons to amino acids.
Transfer RNAs
inserts complementary RNA bases opposite the DNA template strand.
RNA polymerase
gains a modified nucleotide cap and a poly A tail.
Messenger RNA (mRNA)
Particular mRNA codons correspond to particular amino acids
This correspondence between the chemical languages of mRNA and protein is the_____
genetic code
Translation occurs on ________in the cytoplasm as well as on ribosomes that are embedded in the_______
free ribosomes
endoplasmic reticulum (ER).
AUGCCCAAG
AUG
CCC
AAG
methionine
proline
lysine
The first mRNA codon to specify an amino acid is always_____, which attracts an initiator tRNA that carries the amino acid methionine (abbreviated met).
AUG
signifies the start of a polypeptide.
methionine
___ site holds the growing amino acid chain, and the__ site right next to it holds the next amino acid to be added to the chain.
P
A
Elongation halts when the A site of the ribosome has a______, because no tRNA molecules correspond to it
“stop” codon (UGA, UAG, or UAA)
Building a polypeptide. (a) A ________ subunit binds to the initiation complex, and a tRNA bearing a second amino acid (glycine, in this example) forms hydrogen bonds between its anticodon and the mRNA’s second codon at the A site. The first amino acid, methionine, occupies the P site.
large ribosomal
Terminating a polypeptide. (a) A___________ binds to the stop codon, releasing the completed polypeptide from the tRNA and (b) freeing all of the components of the translation complex.
protein release factor
Proteins fold into one or more three-dimensional shapes, or________. This folding is based on chemistry: attraction and repulsion between atoms of the proteins as well as interactions of proteins with chemicals in the immediate environment.
conformations
The amino acid sequence of a polypeptide chain is its _______ structure.
primary (1°)
Chemical attractions between amino acids that are close together in the 1° structure fold the polypeptide chain into its_____ structure, which may form loops, coils, barrels, helices, sheets, or other distinctive shapes..
secondary (2 °)
The two most common secondary structures are
alpha helix and a beta-pleated sheet
Secondary structures wind into larger_____ structures as more widely separated amino acids attract or repel in response to water molecules.
tertiary (3°)
proteins consisting of more than one polypeptide form a _______structure.
Ex.
______, the blood protein that carries oxygen, has four polypeptide chains (see figure 11.1).
The liver protein_____ has 20 identical polypeptides of 200 amino acids each.
quaternary (4°)
Hemoglobin
ferritin
the muscle protein____ is a single polypeptide chain.
myoglobin
Misfolded proteins are tagged with____ and sent through a proteasome for dismantling.
ubiquitin
help conformation arise. Other proteins help new bonds form and oversee folding accuracy.
Chaperone proteins
Ubiquitin attaches to misfolded proteins and escorts them to_____ for dismantling. Protein misfolding is associated with certain diseases.
proteasomes
