Gene Expression Flashcards
What is Heredity?
the genetic transmission of characteristics or traits from parents to their children
What are Genes?
the functional units of heredity, each gene is a piece of a DNA molecule
what is the method of storing information in a DNA molecule
the sequence/order of nucleotides in DNA molecules is a based on a triplet code
what is the triplet code
3 consecutive nucleotides called triplets form the word of the triplet code
chromosomes contain thousands of
genes
what are the two major type of genes
structural genes and regulatory genes
structural genes
DNA sequences that determine specific amino acid sequences in proteins,
such as enzymes; hormones; or structural proteins, such as collagen
regulatory genes
DNA sequences involved in controlling which structural genes are expressed
in a given tissue
what is gene expression
making of proteins from the information stored in DNA
genes expression has two main steps
transcription
translation
TRANSCRIPTION
the synthesis of mRNA, tRNA, and rRNA based on the nucleotide sequence in DNA
why does DNA stay in the nuclues
it is too big to leave through the nuclear pore
complex
when does transcription occur
when a section of a double-stranded DNA molecule unwinds and its complementary strands separate
One of the DNA strands serves as the what during transcription
as the template strand for the
process of transcription.
what happens in terms of alignment in transcription
Nucleotides that form RNA align with the DNA nucleotides in the template strand by complementary base pairing
what is the pairing
RNA -------> DNA A T C G G C U A
ATCGU is basically what
adenine, thymine, cytosine, guanine, uracil
RNA polymerase
is an enzyme that synthesizes the complementary RNA molecule from DNA
DNA polymerase associate with other proteins called
transcription factors
why does DNA polymerase associate with transcription factors
in order to bind to the DNA
at a specific sequence called a promoter
what happens when RNA polymerase attaches to the promoter
it causes
a portion of the DNA molecule to unwind, exposing the nucleotide sequence for that region of the
template strand.
to form mRNA what does RNA go through
The RNA nucleotides are combined by dehydration reactions,
catalyzed by RNA
polymerase, to form mRNA.
Only a small portion of the DNA molecule unwinds at any one time. T or F
true
As complementary nucleotides are added to the mRNA what is happening to RNA polymerase
RNA polymerase moves along the DNA
unwinding the next portion, while the previously unwound section of DNA strands winds back
together.
When RNA polymerase encounters a DNA nucleotide sequence called the terminator what happens
it detaches from the DNA releasing the newly formed mRNA.
The region of a DNA molecule between the promoter and terminator is a
gene
Some regions of a gene that are transcribed to form mRNA do not code what
parts of a protein
The DNA sequence of a gene contains two regions that do not code for proteins they are
flanking untranslated regions
the flanking untranslated regions function for what
regulation of translation
During transcription, the sequence of nucleotides in DNA between the promoter and the
terminator serve as a
template to make an RNA molecule called pre-mRNA
what are exons
sections of the protein coding region of RNA that code for parts of a protein
what are introns
sections of the protein coding region of RNA that code for do not code for parts of a protein
posttranscriptional processing
the modifications pre-mRNA undergoes before leaving the nucleus which produces the functional mRNA
The posttranscriptional processing are
- A 7 –methyl guanosine cap is added to one end of mRNA.
- A series of adenine nucleotides, called a poly-A tail, is added to the other end.
- Splicing
These modifications to the ends of the mRNA ensure what
that mRNA travels from the nucleus to
the cytoplasm and interacts with ribosomes during translation.
what are spliceosomes
enzymes that remove introns from the pre-mRNA and splices exons together
The functional mRNA consists only of
exons
alternative splicing
various combinations of exons are incorporated into mRNA
Which exons, and how many exons, are used to make mRNA can vary between cells of
different tissues, resulting in different mRNAs transcribed from the same gene
what does alternative splicing allow for
allows a single gene to produce more than one specific protein; however, the
various proteins usually have similar functions in different tissues.
Genetic Code
the information contained in mRNA
codons
the genetic code is carried in set of three nucleotide units
what does a codon do
A codon specifies an amino acid during translation.
the codon GAU specifies the amino acid
aspartic acid
the codon CGA specifies
arginine
how many aminoacide exist and how many possible codons
There are only
20 different amino acids, and 64 possible codons exist
an amino acid can have more than one codon true of false
true
the codons for the amino acid arginine include
CGA, CGG, CGU, and CGC
AUG does what
specifies methionine, also acts as a start codon, which signals the beginning of
translation.
UAA, UGA, and UAG act as
stop codons, which signal the end of translation
do stop codons specify amino acids
no they don’t
where does the protein-coding region
of an mRNA begin and end
begin at the start codon
ends at the stop codon
Translation
is the synthesis of proteins
what two things join together in translation and what do they form
mRNA (cytoplasm) + ribosomes (rRNA and proteins)
make new proteins
Transfer RNAs (tRNA) function in translation
carry the amino acids to the ribosome-mRNA
complex. To do this, one end of each kind of tRNA combines with a specific amino acid.
Another
part of the tRNA called the what is it
anticodon
consists of three nucleotides and is complementary to a particular codon of mRNA
On the basis of the pairing relationships between nucleotides, the anticodon can combine only with its
matched codon
tRNA that binds to aspartic acid has the anticodon
CUA
CUA combines with what
the codon GAU of mRNA
Therefore the codon GAU codes for
aspartic acid
Ribosomes align the codons of the
mRNA with the anticodons of tRNA
and then enzymatically join the amino acids of adjacent tRNA molecules.
how does the mRNA move through the ribosome
one codon at a time
With each move, a new tRNA enters the ribosome and
the amino acid is linked to the growing chain, forming a polypeptide
After the initial part of mRNA is used by a ribosome, another ribosome can attach to the mRNA
and begin to make a
protein
polyribosome
The resulting cluster of ribosomes attached to the mRNA
Each ribosome in a polyribosome produces an
identical protein
polyribosomes are an efficient way to use a single mRNA molecule to
produce many copies of the same protein
proproteins
proteins that are longer when first made than they are in their final, functional state.
the extra piece of the molecule is cleaved (cut) off by enzymes
enzymes to make the proprotein into a functional protein
proenzymes
Many proteins are enzymes, and the proproteins of those enzymes
If many
proenzymes were made within cells as functional enzymes what could they do and how is that prevented
digest the cell that made them
Instead, they are made as proenzymes and are not converted to active enzymes until they
reach a protected region of the body, such as inside the small intestine, where they are functional
Other post-translational processing includes:
Adding of side chains to the protein, such as polysaccharides (ex. glycoproteins)
Some proteins are composed of two or more amino acid chains that are joined after each
chain is produced on separate ribosomes. (ex: hemoglobin is made of 4 proteins each made
alone and assemble into a tetramer after translation)
Most of the cells in the body have the same
DNA
The transcription of mRNA in cells is regulated this means what
some DNA is transcribed and other DNA is not
the proteins assoicated with DNA in the nucleus play what kind of role
play a role in regulating the transcription
during development what happens in terms of parts of the DNA
during development, part of the DNA becomes
nonfunctional and is not transcribed, whereas other segments of DNA remain very active.
developing RBC in terms of DNA
in developing red blood cells, the DNA coding for hemoglobin is functional, and
hemoglobin synthesis occurs rapidly. But in most other cells the DNA coding for hemoglobin is
nonfunctional, and little if any hemoglobin is synthesized.
is gene expression in a cell constant and how rapidly does it occur
Gene expression in a single cell is not normally constant, but it occurs more rapidly at some times
than others.
what can Regulatory molecules that interact with the nuclear proteins do
increase or decrease the transcription rate of specific DNA segments.
triiodothyronine (T3), a
hormone released by cells of the thyroid gland, enters cells, such as skeletal muscle cells; interacts
with specific nuclear proteins; and increases specific types of mRNA transcription. what happens as a consequence
the production of certain proteins increases. As a result, an increase in the number of
mitochondria and an increase in metabolism occur in these cells.
“CATGAGTAG
has a meaning, which is used to construct other DNA
molecules, RNA molecules, or proteins
