Unit 6 Lesson 5: Gene expression and Gene Regulation Flashcards
What is gene expression
a process by which genetic information is converted into proteins
Gene expression is the process by which..
Gene expression is the process by which information carried in the DNA of cells is decoded and used to build the proteins needed for those cells to survive.
What are products of gene expression
Everything from eye color, organ function, and immune responses to viruses are products of gene expression.
What is gene regulation
the mechanisms that activate or repress the expression of a gene
How does gene rexpression and regulation occur in prokaryotes and eukaryotes
These processes occur differently in prokaryotes (cells that do not contain organelles, such as nuclei) and eukaryotes (cells that do contain organelles like nuclei).
What are the difference betweeen prokaryotic and eukaryotic cells
First, prokaryotes do not separate their DNA from the cytoplasm using a structure called a nucleus like eukaryotic cells do.
First, prokaryotes do not separate their DNA from the cytoplasm using a structure called a nucleus like eukaryotic cells do.
What does this mean
This means that the moment the enzyme RNA polymerase finishes transcribing DNA into mRNA, a ribosome can immediately attach to the mRNA and begin translating it into protein.
RNA polymerase
an enzyme that copies a DNA genetic sequence into an mRNA sequence
This means that the moment the enzyme RNA polymerase finishes transcribing DNA into mRNA, a ribosome can immediately attach to the mRNA and begin translating it into protein.
What happens becasue of this
Because of this, most gene regulation in prokaryotes focuses on regulating the process of transcription.
prokaryotes tend to be what cellular organsims?
Furthermore, prokaryotes tend to be unicelluar organisms, which consist of only one cell.
Why do prokaryotes need to ensure that genes needed to use the resources in the environment are active while conserving as much energy as possible.
prokaryotes tend to be unicelluar organisms, which consist of only one cell
Because of this, prokaryotes need to ensure that genes needed to use the resources in the environment are active while conserving as much energy as possible. What does this require
This requires fine tuning their gene expression to only use the genes they need at that very moment to survive.
Why are there many gene regulation mechanisms in prokaryotes that directly respond to environmental stimuli.
Because of this, prokaryotes need to ensure that genes needed to use the resources in the environment are active while conserving as much energy as possible. This requires fine tuning their gene expression to only use the genes they need at that very moment to survive. Because of this, there are many gene regulation mechanisms in prokaryotes that directly respond to environmental stimuli.
What does an eukaryote’s nucleus do
Eukaryotes have a nucleus that separates their DNA from the cytoplasm.
What allows eukaryotes to separate the process of transcription and translation
Eukaryotes have a nucleus that separates their DNA from the cytoplasm. This allows eukaryotes to separate the process of transcription and translation
What ablity does separating the process of transcription and translation give eukaryotes
This allows eukaryotes to separate the process of transcription and translation, giving them the ability to manipulate and modify mRNA before translation
Eukaryotes tend to be ?cellular
eukaryotes tend to be multicellular, multiple copies of the same starting cell.
Why do all cells in an organism inheir the same copy of DNA
Because of this, all the cells in an organism inherit the same copy of DNA.
Because of this, all the cells in an organism inherit the same copy of DNA. Where is this DNA nescssary
Part of this DNA is necessary in a specific cell type (such as a skin cell), but the other parts of the DNA are not necessary. For example, in humans, a liver cell uses specific genes within the DNA, and would not need the specific genes used by brain cells.
Why led eukaryores to develop unique ways of packaging DNA t
. For example, in humans, a liver cell uses specific genes within the DNA, and would not need the specific genes used by brain cells. Because of this, eukaryotes have developed unique ways of packaging DNA to silence many genes at a time.
What is chromatin remodeling
the process by which DNA is unwound from its associated protein to allow for transcription or replication
What is the importance of chromatin remolding
chromatin remodeling, and it is an important step in the process of cell differentiation, during which a cell develops and matures into a certain type of cell, such as a liver cell or brain cell.
Your digestive tract is filled with bacteria such as
Escherichia coli (E. coli)
What is E. coli used for
E. coli has become one of the main model organisms that scientists use to study prokaryotes.Scientists have studied these bacteria to learn how gene regulation occurs in prokaryotes.
How does E.Coil bacteria get energy
. E. coli bacteria use a wide variety of sugars to get the energy they need to digest the food you eat. The bacteria need different types of enzymes in order to be able to use each type of sugar found in the food you ingest.
E. coli, like other prokaryotes, organize the genes in their genome into clusters called
Operons
What are operons
a group of related genes that operates together as a functional unit in prokaryotic cells
Opersons are the main way that prokaryotes regualte..
Operons are the main way that prokaryotes regulate gene expression at the transcriptional level.
There are two main types of operons:
inducible and repressible.
What are the most studeied inducible and repressible.
The most studied inducible operon is the lac operon, and the most studied repressible operon is the trp operon.
Note the similarities between the two types of operons.
In both cases, binding of the repressor protein to the operator shuts down the operon. Also, binding of the repressor protein to a molecule related to the function of the operon causes a change in the shape of the repressor protein. This change in shape affects the binding of the repressor protein to the operator.
repressor
a regulatory protein and/or small molecule that inhibits transcription
How have prokaryotes, like E. coli, have become very efficient at using their resources.
By using operons, prokaryotes, like E. coli, have become very efficient at using their resources.
Multicellular eukaryotes all start off as
zygotes
What kind of cells are zygotes
Multicellular eukaryotes all start off as zygotes, which are single cells.
how does zygote create more cells
This zygote then duplicates and copies its DNA to create more cells. This process is repeated until a single cell gives rise to all the cells within the body. Because of this, all the cells in a multicellular eukaryote, like humans, have the same DNA.
If they all have the same DNA, then why does a brain cell behave so differently from a liver cell?
The answer comes from a unique form of gene regulation used by eukaryotes called chromatin remodeling or DNA packaging.
Besides DNA packaging, eukaryotic cells, just like prokaryotic cells, can control how genes are…
transcribed into mRNA.
What is DNA like in prokaryote cells
Recall that prokaryotes do not have a nucleus. The DNA of prokaryotes is in the cytoplasm of the cell. This allows ribosomes in the cytoplasm to immediately begin translating any mRNA that has been transcribed from the DNA. This prevents prokaryotes from modifying or manipulating their mRNA to affect its translation.
What is DNA like in Eukaryote cells
Eukaryotes, on the other hand, have nuclei. This barrier separates the DNA from the cytoplasm. The mRNA produced by transcription must be transported out of the nucleus into the cytoplasm in order to be translated by the ribosome in the cytoplasm. This allows eukaryotes to modify and manipulate their RNA in a process known as RNA processing.
RNA processing
a change RNA undergoes in the cell nucleus to become a mature mRNA molecule
The DNA of eukaryotes is different from prokaryotes. Elaborate
In prokaryotes, the entire region of a gene that codes for a protein is translated into protein. In eukaryotes, on the other hand, the segments of the gene that will be expressed as protein are known as exons.
exon
a portion of a gene that is expressed into protein
What are between exons
Between these exons are segments of DNA that are transcribed into the mRNA initially, but they are removed before the mRNA is transported to the cytoplasm for translation. These regions that will not be made into protein are known as introns.
What are introns
a portion of a gene that is not expressed into protein
When must introns be removed
Introns must be removed from the initial mRNA, or pre-mRNA, before the mRNA can be transported to the cytoplasm for translation by the ribosome
What is the porcess of removing introns called
The process of removing introns from the pre-mRNA is known as RNA splicing.
RNA splicing does not always put all the exons of a gene back together. What happens in this case
This process can make different mRNAs from the same pre-mRNA by putting the exons together in different ways. This allows eukaryotes to produce several different mRNAs and, therefore, several different proteins from the same gene.
Mutations in the gene near the boundary of exons and introns can cause problems with RNA splicing. Waht does this allow
This allows an intron to remain in the mRNA. Because of this extra mRNA, the protein that is translated from the wrongly spliced mRNA does not function correctly.
After RNA splicing, two modifications are made to the mRNA in eukaryotes. Elaborte
First, a structure, known as a 5’-cap (pronounced “5 prime cap”), is added to the front of the mRNA. This cap interacts with the nuclear pores in the nuclear envelope of the nucleus, allowing the mRNA to be transported into the cytoplasm. Finally, adenine nucleotides are added to the end of the mRNA. This structure is known as the poly(A) tail. The number of adenines can vary, and this structure acts as a timer. When in the cytoplasm, there are enzymes that will slowly degrade these poly(A) tails. Once these tails are fully degraded, the mRNA is destroyed completely. Therefore, the cell can modify the length of this tail to make the mRNA last longer. Longer tails allow more time for translation, which results in more protein being produced from the mRNA.
Regulation of gene expression at the translational and post-translational levels works similarly in both
Regulation of gene expression at the translational and post-translational levels works similarly in both prokaryotes and eukaryotes. The specific proteins and processes involved are, or course, different between the two types of cells, but there are similarities between the two.
In order to prevent translation of the mRNA into protein what must be done
In order to prevent translation of the mRNA into protein once the mRNA has been transported to the cytoplasm, the cell must interfere with the ability of the ribosome to translate the mRNA.
What are 2 ways a cells can prevent translation of the mRNA into the protein
There are two ways for the cell to do this: destroy the mRNA or prevent the mRNA from binding to the ribosome.
What must be done to destroy the mRNA
In order to destroy the mRNA, both prokaryotes and eukaryotes have evolved systems that perform RNA silencing or RNA interference.
RNA silencing
a way for the cell to control the translation of an mRNA using microRNAs; also known as RNA interference
How is the process of RNA sliencing simialr in both prokaryotes and eukaryotes
. Although the exact proteins and enzyme involved in these processes are different between prokaryotes and eukaryotes, they both involve using small pieces of RNA called microRNA.
What does microRNAs do
These microRNAs have specific sequences that allow them to bind to specific mRNAs in the cytoplasm. Once bound to the mRNA, they flag the mRNA for degradation by certain enzymes in the cytoplasm.
What does the destruction of the mRNA do
The destruction of the mRNA prevents protein from being made by the ribosome from this mRNA.
The second way involves preventing the mRNA from binding to the ribosome. Elaborate
e. Most mRNAs have a region, called the untranslated region or UTR, near the beginning and end of the molecule that is not translated into protein. These UTRs typically have binding sites for proteins that when bound can prevent the mRNA from binding the ribosome. This method of translational control is more reversible than the RNA silencing method described previously. The mRNA is not destroyed using this method. The cell can modify the protein bound to the mRNA so it will release the mRNA, allowing it to be translated.
Post-translational control involves affecting the ability of the protein to perform its function or destroying the protein. There several ways a cell can affect the function of a protein. Explain
First, after an mRNA is translated into a polypeptide strand, that polypeptide strand must fold into a particular shape to become active. Because of this, the cell can take advantage of this to affect the function of the protein by either helping the protein fold correctly or preventing the protein from folding correctly. Second, many proteins require more modifications to become active. For example, some proteins involve multiple polypeptide strands that must come together to form a complex. Other proteins require the addition of chemical groups to be added before the protein becomes active. This is one of the more popular ways of controlling protein function, and one of the most popular chemical groups is the phosphate group, which is a phosphorus atom chemically bonded to four oxygens. The addition of a phosphate group typically activates the protein, while the removal of the phosphate group typically inactivates the protein. Finally, the cell can control when the protein becomes destroyed. This allows the cell to control the lifetime of the protein.
What might happen if a eukaryotic cell could not regulate its gene expression?
The cell would make all the proteins that its DNA codes for. There would be no repression of gene expression. The cell would waste a lot of energy making proteins that it did not need.
What are three ways a cell can regulate the proteins it produces?
transcriptional control, post-transcriptional control (which includes RNA processing), translational control (which includes RNA silencing or RNA interference), and post-translational control
What is the difference between gene expression and gene regulation?
Gene expression describes the process by which genetic information is converted into proteins. Gene regulation describes processes by which the expression of a gene is induced, turned on, or repressed, turned off.
What is a promoter, and what is its function?
A promoter is a noncoding part of a gene. It serves as the binding site for the enzyme RNA polymerase that will transcribe the gene into mRNA. This site typically has regulatory sites near it that either enhance or limit the ability of the RNA polymerase to bind to it.
Suppose an mRNA molecule for an enzyme has been transcribed, and the mRNA is prevented from being translated into a protein. This is known as _______
transcriptional control
translational control
chromatin remodeling
RNA processing
B. translational control
Explain how gene regulation results in the formation of specialized cells in multicellular organisms. How is this different in a prokaryotic cell, which is not specialized?
The cells of a multicellular organism do not make all the proteins that are coded for in their DNA. Instead, each kind of cell makes only those proteins that it needs for its specific functions. A prokaryotic cell must perform all the functions of the organism. It must make all the proteins that are coded in its DNA. To turn off certain proteins, the cells of a multicellular organism use a combination of the gene regulation techniques, including chromatin remodeling, transcriptional control, RNA processing, translational control, and post-translational control to only use some of the DNA.
transcription factors
a class of proteins that regulates transcription in eukaryotes by interacting with RNA polymerase.
promoter
a segment in DNA that binds with the enzyme RNA polymerase
