Biology - Chapter 13
Why are mutations important?
Without mutations, organisms cannot evolve, because mutations are the source of genetic variability in a species
How do you read the codon chart?
You start at the middle of the circle and move outward to read the codon chart
RNA polymerase binds to regions of DNA called __________________, which are "start" signals for transcription.
promoters
What is the role of rRNA in translation?
rRNA help hold ribosomal proteins in place and help locate the beginning of the mRNA message. rRNA may even carry out the chemical reaction that joins amino acids together.
Describe the role of rRNA during translation.
rRNA helps hold ribosomal proteins in place and helps locate the beginning of the mRNA message. rRNA may even carry out the chemical reaction that joins amino acids together.
The cellular machinery that replicates DNA inserts an incorrect base:
roughly once in every 10 million bases
Regulating gene expression is especially important in:
shaping the way a multicellular organism develops
What is the function of transfer RNA (tRNA)?
tRNA transfers each amino acid to the ribosome as it is specified by the coded messages in mRNA
(Study the DNA, pre-mRNA, and final mRNA diagrams on page 3 of 13.1 RNA Worksheet.)
(DNA, pre-mRNA, final mRNA)
(Study Lesson 13.3 Chromosomal Mutations Diagrams)
(Deletion, Duplication, Inversion, Translocation)
(Study the diagram on page 2 of Transcription Practice Worksheet of a mRNA strand that complements the DNA strand CCA ATG, including the backbone of the mRNA strand)
(GGU UAC)
(Study picture of nucleotide on page 1 of Transcription Practice Worksheet.)
(Ribose (sugar), Nitrogenous Base, Phosphate Group - Nucleotide)
What is the "lac" operon?
A cluster of 3 genes that must be turned on together before the bacterium can use the sugar lactose as a food
What are the steps of transcription?
1) RNA polymerase binds to DNA and separates the DNA strands. 2) One strand of DNA is used as a template from which to assemble nucleotides into a complementary strand of RNA. 3) RNA detaches from the DNA template and goes through editing. 4) Once the exons are put together, mRNA leaves the nucleus and travels towards the ribosomes.
How do the mutagens affect the DNA?
1) Some compounds interfere with base-pairing, increasing the error rate of DNA replication. 2) Others weaken the DNA strand, causing breaks and inversions that produce chromosomal mutations. 3) Cells can sometimes repair the damage; but when they cannot, the DNA base sequence changes permanently.
How many strands are in RNA?
1
Sum up the steps of Protein synthesis.
1) DNA carries information for specifying the traits of an organism. 2) The cell uses the sequence of bases in DNA as a template for making mRNA. 3) The codons of mRNA specify the sequence of amino acids in a protein. Proteins, in turn, play a key role in producing an organism's traits.
What are the three types of RNA? (use both the abbreviations and names)
1) Messenger RNA (mRNA), 2) Ribosomal RNA (rRNA), 3) Transfer RNA (tRNA)
What are the three primary types of RNA? And what are their functions?
1) Messenger RNA (mRNA): Carry copies of instructions needed for assembling amino acids into proteins. 2) Ribosomal RNA (rRNA): Proteins are assembled on ribosomes, small organelles composed of two subunits. These ribosome subunits are made up of several ribosomal RNA proteins and as many as 80 different proteins. 3) Transfer RNA (tRNA): Transfers each amino acid to the ribosome as it is specified by the coded messages in mRNA.
In what two ways is gene regulation in eukaryotes different from gene regulation in prokaryotes?
1) Most eukaryotic genes are controlled individually. 2) Eukaryotic cells have more complex regulatory sequences than those of the lac repressor system.
What are the steps of transcription?
1) RNA polymerase binds to DNA and separates the DNA strands. 2) One strand of DNA is used as a template from which to assemble nucleotides into a complementary strand of RNA. 3) RNA detaches from the DNA template and goes through editing. 4) Once the exons are put together, mRNA leaves the nucleus and travels to the ribosomes.
What are two possible explanations why cells make large RNA molecules and then throw away parts of them?
1) Some pre-mRNA molecules may be cut and spliced in different ways in different tissues, making it possible for a single gene to produce several different forms of RNA. 2) Introns and exons may also play a role in evolution, making it possible for very small changes in DNA sequences to have dramatic effects on how genes affect cellular function.
What are some examples of how the transcription factors control gene expression?
1) Some transcription factors enhance transcription by opening up tightly packed chromatin. 2) Others help attract RNA polymerase. 3) Still others block access to certain genes.
What are the three differences between RNA and DNA?
1) The sugar in RNA is ribose instead of deoxyribose, 2) RNA is generally single-stranded and not double-stranded, 3) RNA contains uracil in place of thymine
How does RNA differ from DNA?
1) The sugar in RNA is ribose instead of deoxyribose. 2) RNA is generally single-stranded and not double-stranded. 3) RNA contains uracil in place of thymine.
What are the three differences between RNA and DNA?
1) The sugar in RNA is ribose instead of deoxyribose. 2) RNA is generally single-stranded and not double-stranded. 3) RNA contains uracil in place of thymine.
Name the three types of RNA and what they do.
1) Transfer RNA (tRNA) - transfers each amino acid to the ribosome as it is specified by the coded messages in mRNA. 2) Messenger RNA (mRNA) - carry copies of instructions needed for assembling amino acids into proteins. 3) Ribosomal RNA (rRNA) - forms an important part of both subunits of the ribosomes, the cell structures where proteins are assembled.
What are the steps of translation?
1) Translation begins when a ribosome attaches to an mRNA molecule in the cytoplasm. 2) As the ribosome reads each codon of mRNA, it directs tRNA to bring the specified amino acid into the ribosome. 3) One at a time, the ribosome then attaches each amino acid to the growing chain. 4) When the ribosome reaches a stop codon, it releases both the newly formed polypeptide and the mRNA molecule, completing the process of translation.
What are the steps of translation?
1) mRNA is transcribed in the nucleus and then enters the cytoplasm for translation and attaches to a ribosome. 2) As the ribosome reads each codon of mRNA, it directs tRNA to bring the specified amino acid into the ribosome. 3) One at a time, the ribosome then attaches each amino acid to the growing chain. 4) When the ribosome reaches a stop codon, it releases both the newly formed polypeptide and the mRNA molecule, completing the process of translation.
What is a TATA box? What does a TATA box do?
A TATA box is a short region of DNA containing the sequence TATATA or TATAAA that is usually found just before a gene. The TATA box binds a protein that helps position RNA polymerase by marking a point just before the beginning of a gene.
How many strands are in DNA?
2
As many as ______ different amino acids are commonly found in polypeptides.
20
How many amino acids are there?
20
How many possible combinations of codons are there for RNA?
64 possible three-base codons
What makes up a nucleotide in RNA and DNA?
A 5-carbon sugar, a phosphate group, and a nitrogenous base. RNA's nucleotides consist of ribose, a phosphate group, and a nitrogenous base (adenine, cytosine, uracil, and guanine). DNA's nucleotides consist of deoxyribose, a phosphate group, and a nitrogenous base (adenine, cytosine, thymine, and guanine).
What can you think of an RNA molecule as?
A disposable copy of a segment of DNA, a working copy of a single gene
What real-life item are master control genes like?
A fuse box
What is an operon?
A group of genes that are regulated together
Why do you think it is important for there to be so many combinations of amino acid chains to make up proteins?
A large amount of amino acid combinations in proteins allows for genetic diversity in the organism
What is the difference between DNA and RNA in the analogy used to explain the roles of DNA and RNA in the production of proteins?
A master plan has all the information needed to construct a building. Builders never bring a valuable master plan to the building site, where it might be damaged or lost. Instead, they prepare inexpensive, disposable copies of the master plan called blueprints. Similarly, the cell uses DNA "master plan" to prepare RNA "blueprints." The DNA molecule stays safely in the cell's nucleus, while RNA molecules go to the protein-building sites in the cytoplasm—the ribosomes.
Describe insertion in gene (point) mutation.
A point mutation in which one base is inserted into the DNA sequence
Describe deletion in gene (point) mutation.
A point mutation in which one base is removed from the DNA sequence
What are the homeotic genes?
A set of master control genes that regulates organs that develop in specific parts of the body
What is the TATA box?
A short region of DNA containing the sequence TATATA or TATAAA that is usually found just before a gene
In regulating genes in prokaryotes, what is a promoter (P)?
A site where RNA-polymerase can bind to begin transcription
How long is miRNA?
About 20 base pairs in length
What are the four nitrogenous bases of RNA?
Adenine, cytosine, guanine, and uracil
What bases are in DNA?
Adenine, guanine, thymine, and cytosine
What bases are in RNA?
Adenine, guanine, uracil, and cytosine
Explain how the process of RNA interference works.
After they are produced by transcription, the small interfering RNA molecules fold into double-stranded hairpin loops. An enzyme called the "Dicer" enzyme cuts, or dices, these double-stranded loops into microRNA (miRNA), each about 20 base pairs in length. The two strands of the loops then separate. One of the miRNA pieces attaches to a cluster of proteins to form what is known as a silencing complex. The silencing complex binds to and destroys any mRNA containing a sequence that is complementary to the miRNA. The miRNA sticks to certain mRNA molecules and stops them from passing on their protein-making instructions. Blocking gene expression by means of an miRNA silencing complex is known as RNA interference (RNAi).
What is the smallest unit of a protein called?
Amino acid
What is an anticodon? Where is it found?
An anticodon is three unpaired bases in every tRNA molecule that is complementary to one mRNA codon. It is found in the cytoplasm.
A gene that codes for one of the polypeptide chains of the blood protein hemoglobin lies on chromosome 11 in humans. A substitution mutation in that gene causes the amino acid valine to be incorporated into hemoglobin in a place where glutamic acid would normally lie. The result is sickle cell disease. Explain how a change in a single base in DNA can bring about such a serious disorder.
An incorrect base in a DNA molecule could result in an incorrect codon in the mRNA. This codon will cause the amino acid being assembled to be incorrect, creating a protein that has the wrong function and shape.
What is an operon?
An operon is a group of genes that are regulated together
What is the second step of translation?
As the ribosome reads each codon of mRNA, it directs tRNA to bring the specified amino acid into the ribosome
Give a description of the assembly of a polypeptide.
As the ribosome reads each codon of mRNA, it directs tRNA to bring the specified amino acid into the ribosome. One at a time, the ribosome then attaches each amino acid to the growing chain.
What is RNAi?
Blocking gene expression by means of an miRNA silencing complex; RNA interference
How are genes regulated in eukaryotic cells?
By binding DNA sequences in the regulatory regions of eukaryotic genes, transcription factors control the expression of those genes
How are proteins made?
By joining amino acids into long chains called polypeptides
What is the resulting mRNA strand that would be copied from the DNA of the following strand: GGC TAT ATC CTG CGC TAT ACG CTA?
CCG AUA UAG GAC GCG AUA UGC GAU
(Look at 13.2 Ribosomes and Protein Synthesis Worksheet Questions 8-10) What is the codon for leucine?
CUG
Why is gene regulation in eukaryotes more complex than in prokaryotes?
Cell specialization requires genetic specialization, yet all of the cells in a multicellular organism carry the same genetic code in their nucleus. Complex gene regulation in eukaryotes is what makes specialization possible.
What does "differentiation" mean relating to gene regulation?
Cells become specialized in structure and function
What are some examples of chemical mutagens?
Certain pesticides, a few natural plant alkaloids, tobacco smoke, and environmental pollutants.
Explain how the process of RNA interference works.
Certain small RNA molecules fold into loops. The Dicer enzyme cuts them into microRNA (miRNA). The strands then separate. An miRNA piece attaches to a cluster of proteins to form a silencing complex. The silencing complex binds to and destroys an mRNA molecule that contains a base sequence complementary to the miRNA. In this way, it blocks gene expression.
What are mutagens?
Chemical or physical agents in the environment
What is an example of the effect of a gene point mutation using substitution?
Cystic fibrosis
Where does translation take place?
Cytoplasm
What is the first step of protein synthesis?
DNA carries information for specifying the traits of an organism
Where is DNA found in the cell? Where is RNA found in the cell?
DNA is found in the cell's nucleus, while RNA is found in ribosomes within the cytoplasm
Why isn't DNA used to make its own amino acid chains outside of the nucleus?
DNA needs to stay in the nucleus to remain protected. This allows DNA to remain undamaged and consistent.
The central dogma of molecular biology is the information is transferred from:
DNA to RNA to protein
How are prokaryotic genes regulated?
DNA-binding proteins in prokaryotes regulate genes by controlling transcription
How do DNA-binding proteins in prokaryotes regulate genes?
DNA-binding proteins in prokaryotes regulate genes by controlling transcription
Describe a deletion chromosomal mutation.
Deletion involves the loss of all or part of a chromosome
What are the types of chromosomal mutations?
Deletion, duplication, inversion, and translocation
What is the sugar in DNA?
Deoxyribose
A mutation that produces an extra copy of all or part of a chromosome
Duplication
Describe a duplication chromosomal mutation.
Duplication produces an extra copy of all or part of a chromosome
When does most of the work of making RNA take place?
During transcription
What is the role of tRNA in translation?
During translation, each time an amino acid is added to the growing chain, a tRNA molecule forms base pairs with its complementary sequence on the messenger RNA (mRNA) molecule, ensuring that the appropriate amino acid is inserted into the protein
What is a codon?
Each three-letter "word" in mRNA
Which scientist first identified a specific group of genes that controls the identities of body parts in the embryo of the fruit fly?
Edward B. Lewis
____________ are spliced together to make the final mRNA.
Exons
What are exons?
Exons are the remaining pieces. They are spliced back together to form the final mRNA.
A kind of mutation that can change every amino acid that follows the point of mutation
Frameshift mutation
What is another name given to insertion and deletion point mutations? Why is it called this?
Frameshift mutations because they shift the "reading frame" of the genetic message.
What do frameshift mutations do?
Frameshift mutations can change every amino acid that follows the point of the mutation and can alter a protein so much that it is unable to perform its normal functions
(Look at 13.2 Ribosomes and Protein Synthesis Worksheet Questions 8-10) What is the anticodon for leucine?
GAC
What are the codons for alanine?
GCG, GCA, GCC, GCU
The way in which DNA, RNA, and proteins are all involved in putting genetic information into action in living cells is called:
Gene expression
What are the two categories mutations fall under?
Gene mutations and chromosomal mutations
The instructions for assembling proteins are contained in the:
Genes
What does DNA tell the cell to do?
Genes contain coded DNA instructions that tell cells HOW TO BUILD PROTEINS
Why do you think a comparison was made between a library full of books and a bacteria with 4000 genes?
Genes contain the information needed for cells to function like books contain information. There are also many books in a library like there are many genes in the bacteria. Moreover, all the books in the library cannot be used at the same time like all the genes in a bacteria cannot be used all at once.
For which amino acid is GGA a codon? (Use codon wheel)
Glycine
(Study diagram of the general structure of an amino acid on page 1 of 13.2 Ribosomes and Protein Synthesis Guided Notes paper.)
H H O \ I // N - C - C / I \ H R OH
Why are homeobox genes important?
Homeobox genes code for transcription factors that activate other genes that are important in cell development and differentiation
A group of homeobox genes
Hox genes
In flies, the group of homeobox genes that determines the identities of each segment of a fly's body is the group known as:
Hox genes
What are the Hox genes in a fruit fly responsible for?
Hox genes determine the identities of each segment of a fly's body
Explain what happens with deletion point mutations.
In a deletion, one base is removed from the DNA sequence. If a nucleotide is deleted, the bases are still read in groups of three, but now those groupings shift in every codon that follows the mutation.
Deletion can happen as a gene mutation or as a chromosomal mutation. What is the difference?
In a gene mutation, a deletion happens when a base is removed from the DNA sequence. In a chromosomal mutation, deletion involves the loss of all or part of a chromosome.
Explain what happens with substitution point mutations.
In a substitution, one base is changed to a different base. Substitutions usually affect no more than a single amino acid, and sometimes they have no effect at all.
Explain what happens with insertion point mutations.
In an insertion, one base is inserted into the DNA sequence. If a nucleotide is added , the bases are still read in groups of three, but now those groupings shift in every codon that follows the mutation.
How does the cell make RNA?
In transcription, segments of DNA serve as templates to produce complementary RNA molecules
What is the "central dogma" of molecular biology?
Information is transferred from DNA to RNA to protein
The addition of a base to the DNA sequence
Insertion
___________ are portions of RNA that are cut out and discarded.
Introns
What is the second possible explanation as to why cells make large RNA molecules and then throw away parts of them?
Introns and exons may also play a role in evolution, making it possible for very small changes in DNA sequences to have dramatic effects on how genes affect cellular function
What are introns?
Introns are the portions that are cut out and discarded. In eukaryotes, introns are taken out of pre-mRNA molecules while they are still in the nucleus.
A chromosomal mutation that reverses the direction of parts of a chromosome
Inversion
Describe a inversion chromosomal mutation.
Inversion reverses the direction of parts of a chromosome
Explain how gene regulation makes cell specialization possible.
It allows particular genes to be expressed in some kinds of cells but not others
What environmental factor influences gene expression in the following scenario: a tadpole in a drying pond?
Lack of water
What impact does substitution have on an organism?
Little to no impact
What are polypeptides?
Long chains of amino acids which make up proteins
For which amino acid is AAA a codon? (Use codon wheel)
Lysine
Where does RNA polymerase bind?
RNA polymerase binds only to promoters
How are many mutations produced? Give an example.
Many mutations are produced by errors in genetic processes. For example, some point mutations are caused by errors during DNA replication.
Summarize the effects of mutations on living things.
Many mutations have little or no effect, but some can be harmful or beneficial
What controls the development of cells and tissues in multicellular organisms?
Master control genes are like switches that trigger particular patterns of development and differentiation in cells and tissues
The m in mRNA stands for:
Messenger
What is metamorphosis?
Metamorphosis involves a series of transformations from one life stage to another, such as the transformation of a tadpole to an adult bullfrog. It is typically regulated by a number of external (environmental) and internal (hormonal) factors.
(Look at 13.2 Ribosomes and Protein Synthesis Worksheet Questions 8-10) List the amino acids in the order they would appear in the polypeptide coded for by this mRNA.
Methionine, phenylalanine, lysine, leucine
What is RNA's primary role?
Most RNA molecules are involved in PROTEIN SYNTHESIS only. RNA controls the assembly of amino acids into proteins. Each type of RNA molecule specializes in a different aspect of this job.
A heritable change in genetic information
Mutation
What are mutations?
Mutations are heritable changes in genetic information
What are the examples of beneficial effects on mutations?
Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments. For example, mutations have helped many insects resist chemical pesticides. Some mutations have enabled microorganisms to adapt to new chemicals in the environment. Polyploid plants, such as bananas and limes, are also produced by beneficial mutations. Polyploid plants are often larger and stronger than diploid plants and occur naturally in citrus plants, often through spontaneous mutations.
What are gene mutations?
Mutations that produce changes in a single gene
What are chromosomal mutations?
Mutations that produce changes in whole chromosomes
What are the building blocks of RNA?
Nucleotides
What environmental factor influences gene expression in the following scenario: E. coli with limited food supply?
Nutrient availability
Where are the two regulatory regions, the promoter and operator, found?
On one side of the operon's three genes
What is the fourth step of transcription?
Once the exons are put together, mRNA leaves the nucleus and travels to the ribosomes
What is the third step of translation?
One at a time, the ribosome then attaches each amino acid to the growing chain
Describe substitution in gene (point) mutation.
One base is changed to a different base
What is the second step of transcription?
One strand of DNA is used as a template from which to assemble nucleotides into a complementary strand of RNA
Whether the organism is a pea plant or a human being, the information in the DNA of the cell's nucleus directs synthesis of proteins in the cytoplasm. Why, then, are pea plants and human beings so different?
Pea plants and humans contain different genetic information that makes us separate organisms with unique traits. We contain different DNA that instructs the construction of different proteins with different functions and shapes.
What holds the amino acids together in the long chain?
Peptide bonds
A change in one or a few nucleotides that occur at a single point in the DNA sequence
Point mutation
What are point mutations?
Point mutations are mutations that involve changes in one or a few nucleotides. They occur at a single point in the DNA sequence, generally during replication.
The condition in which an organism has extra sets of chromosomes
Polyploidy
Why can prokaryotes not use all the genes in a bacteria at the same time?
Prokaryotes are single-celled and have limited energy
What are promoters?
Promoters are the regions of DNA that have specific bases sequences. Promoters act as signals in the DNA molecule that show RNA polymerase exactly where to begin making RNA.
What is the function of ribosomal RNA (rRNA)?
Proteins are assembled on ribosomes, small organelles composed of two subunits. These ribosome subunits are made up of several ribosomal RNA proteins and as many as 80 different proteins. (rRNA provides a functional and structural role within the ribosome)
Why are proteins so important to living things? What do they do?
Proteins are microscopic tools, each specifically designed to build or operate a component of a living cell. Many proteins are enzymes, which catalyze and regulate reactions. (PROTEINS TELL ORGANISMS HOW TO FUNCTION)
What is the third way in which RNA differs from DNA?
RNA contains uracil in place of thymine
What is the third step of transcription?
RNA detaches from the DNA template and goes through editing
What does editing of RNA do?
RNA editing cuts out bits and pieces from RNA molecules that need to be omitted before they can go into action
Blocking gene expression by means of an miRNA silencing complex
RNA interference (RNAi)
What is the second way in which RNA differs from DNA?
RNA is generally single-stranded and not double-stranded
The enzyme ___________________________ binds to DNA during transcription.
RNA polymerase
What is the first step of transcription?
RNA polymerase binds to DNA and separates the DNA strands
What enzyme is used for transcription? What does it do?
RNA polymerase is the enzyme used for transcription. RNA polymerase binds to DNA during transcription and separates the DNA strands. RNA polymerase them uses one strand of DNA as a template from which to assemble nucleotides into a complementary strand of RNA.
What is a benefit of understanding the use of RNAi?
RNAi technology is a powerful way to study gene expression in the laboratory. It also holds the promise of allowing medical scientists to turn off the expression of genes from viruses and cancer cells, and it may provide new ways to treat and perhaps even cure diseases.
What is the sugar in RNA?
Ribose
Ribosomes are composed of roughly how many proteins and different rRNA molecules?
Ribosomes are composed of roughly 80 proteins and three or four different rRNA molecules
What role does the ribosome play in assembling proteins?
Ribosomes use the sequence of codons in mRNA to assemble amino acids into polypeptide chains
How often do errors occur during DNA replication?
Roughly once in every 10 million bases
What impact does deletion have on an organism?
Significant impact
What impact does insertion have on an organism?
Significant impact
Why are mutations caused by stressful environmental conditions actually helpful?
Since mutations may sometimes give such bacteria new traits, such as the ability to consume a new food source or to resist a poison in the environment, this is actually helpful to an organism.
What is microRNA and how is it related to mRNA?
Small RNA molecules are called microRNA. They attach to certain mRNA molecules and stop them from passing on their protein-making instructions.
What role do small RNA molecules (non-mRNA, tRNA, rRNA) play in regulating gene expression?
Small RNA molecules play a powerful role in regulating gene expression by interfering with mRNA
What are some examples of physical mutagens?
Some forms of electromagnetic radiation, such as X-rays and ultraviolet light.
What is the first possible explanation as to why cells make large RNA molecules and then throw away parts of them?
Some pre-mRNA molecules may be cut and spliced in different ways in different tissues, making it possible for a single gene to produce several different forms of RNA
What role do homeobox genes play in cell differentiation?
They code for transcription factors that activate other genes important in cell development and differentiation
What other conditions can cause mutations to occur?
Stressful environmental conditions may cause some bacteria to increase mutation rates. In addition, some mutations may arise from mutagens.
The change of one base to another in a DNA sequence
Substitution
Describe the outcome of substitution in gene (point) mutation.
Substitutions usually affect no more than a single amino acid, and sometimes they have no effect at all. It has little to no impact on the organism.
What are the three types of point mutations?
Substitutions, insertions, and deletions.
What three environmental factors can influence gene expression?
Temperature, salinity, and nutrient availability
What does the "dicer" enzyme do?
The "dicer" enzyme cuts, or dices, the double-stranded loops into microRNA (miRNA)
What happens when cells cannot repair the damage caused by a mutagen?
The DNA base sequence changes permanently
What does a TATA box do?
The TATA box binds a protein that helps position RNA polymerase by marking a point just before the beginning of a gene
An exception to the central dogma is:
The ability of some viruses to transfer information from RNA to DNA
Describe the outcome of deletion in gene (point) mutation.
The bases are still read in groups of three, but now those groupings shift in every codon that follows the mutation. It has a significant impact on the organism.
Describe the outcome of insertion in gene (point) mutation.
The bases are still read in groups of three, but now those groupings shift in every codon that follows the mutation. It has a significant impact on the organism.
Explain how the gene can be turned off and on to allow the bacteria to break down lactose.
The binding of the lac repressor protein switches the operon "off" by preventing the transcription of its genes. However, in the presence of lactose, the operon is automatically switched on.
What turns the lac operon off?
The binding of the repressor protein switches the operon "off" by preventing the transcription of its genes
Where can you find DNA in a eukaryotic cell?
The cell nucleus
The master plan of a building shows how to build and place important parts of the building, such as walls, pipes, and electrical outlets. On the building site, workers use copies of the master plan called blueprints to show them what to do. The master plan is kept in the office. Explain how mRNA works like a blueprint in constructing proteins.
The cell uses DNA, the "master plan," to prepare RNA or the "blue prints." The DNA molecule stays safely in the cell's nucleus, while RNA molecules go to the protein-building sites in the cytoplasm - the ribosomes. mRNA carries copies of instructions needed for assembling amino acids into proteins. These instructions are the blueprint, while ribosomes serve as the construction site where proteins are made.
What is the second step of protein synthesis?
The cell uses the sequence of bases in DNA as a template for making mRNA
Name a place in the EUKARYOTIC cell where you will find DNA.
The cell's nucleus
What can you find by reading a codon wheel from the inside out?
The codon associated with each amino acid
What is the third step of protein synthesis?
The codons of mRNA specify the sequence of amino acids in a protein. Proteins, in turn, play a key role in producing an organism's traits
Where does transcription take place in prokaryotes?
The cytoplasm
Name the two places in the cell where you can find RNA.
The cytoplasm and nucleus
What is translation?
The decoding of an mRNA message into a protein
What are the examples of harmful effects of mutations?
The defective proteins produced by harmful mutations can disrupt normal biological activities, and result in genetic disorders. Some cancers, for example, are the product of mutations that cause the uncontrolled growth of cells. Sickle cell disease is also caused by a point mutation in one of the polypeptides found in hemoglobin, the blood's principal oxygen-carrying protein. (CANCER AND SICKLE CELL DISEASE)
Many research studies have shown that different species may possess some of the exact same genes but show vastly different traits. How can that happen?
The difference arises not from the genes themselves but from how they are regulated and expressed. For example, a gene may be turned on at a different time in one species than in another. Perhaps environmental factors have an effect, too.
How do mutations affect genes?
The effects of mutations on genes vary widely. Some have little or no effect; and some produce beneficial variations. Some negatively disrupt gene function. Mutations often produce proteins with new or altered functions that can be useful to organisms in different or changing environments.
What is the first step in decoding the genetic instructions?
The first step in decoding the genetic instructions is to copy part of the base sequence from DNA into RNA. RNA then uses the base sequence copied from DNA to direct the production of proteins.
What is the first step in decoding the genetic messages?
The first step in decoding the genetic messages is transcribing a nucleotide base sequence from DNA to RNA. This transcribed information contains a code for making proteins.
How are genes organized in bacteria?
The genes in bacteria are organized into operons
What is the genetic code and how is it read?
The genetic code is read three "letters" at a time, so that each "word" is three bases long and corresponds to a single amino acid
What is the function of the genes in the lac operon of E. coli?
The lac operon in E. coli must be turned on before the bacterium can use the sugar lactose as a food
How would E. coli respond to a limited food supply?
The lac operon is switched on when lactose is the only food source
All organisms are mostly the same in:
The molecular biology of their genes
What are the words along the outside of the circle on a codon?
The names of amino acids
What is one of the most interesting discoveries in molecular biology?
The near-universal nature of the genetic code (Although some organisms show slight variations in the amino acids assigned to particular codons, the code is always read three bases at a time and in the same direction)
What happens after the RNA is edited?
The remaining pieces of the exons are spliced back together to form the final mRNA
Where can you find RNA?
The ribosomes (protein-building sites) within the cytoplasm
What influences the shape of a protein?
The sequence of amino acids
What determines the function of a protein?
The shape of the protein
What is the function of the "silencing complex"?
The silencing complex binds to and destroys any mRNA containing a sequence that is complementary to the miRNA
How can the environment affect the process of metamorphosis?
The speed of metamorphosis is determined by various environmental changes that are translated into hormonal changes, with the hormones functioning at the molecular level
What is the start codon? Why is it important?
The start codon is the methionine codon AUG. Methionine serves as the initiation, or "start" codon for protein synthesis.
What is the first way in which RNA differs from DNA?
The sugar in RNA is ribose instead of deoxyribose
How would a tadpole respond to a drying pond?
The tadpole may speed up its metamorphosis
At what level do transcription factors regulate gene expression?
The transcription level
What is gene expression?
The way in which DNA, RNA, and proteins are involved in putting genetic information into action in living cells
What are the primary structures found in RNA that are similar to DNA?
They are both nucleic acids that consist of a long chain of nucleotides. These nucleotides consist of a 5-carbon sugar, a phosphate group, and a nitrogenous base.
What is in the lac operon in E. coli?
Three genes
What does the latin word "mutare" mean?
To change
How do prokaryotes conserve energy?
To conserve energy and resources, prokaryotes regulate their activities, producing only those genes necessary for the cell to function
What is one of the reasons prokaryotes regulate their activities?
To conserve energy and resources, prokaryotes regulate their activities, producing only those genes necessary for the cell to function
What are transcription factors and what do they do?
Transcription factors are DNA-binding proteins that control the expression of eukaryotic genes by binding DNA sequences in the regulatory regions of those genes
Where does transcription take place in eukaryotes?
Transcription takes place in the cell nucleus. Then, transcription moves to the cytoplasm to play a role in the production of proteins.
What is the difference between transcription and translation?
Transcription takes place in the nucleus, while translation takes place in the cytoplasm in ribosomes. Additionally, translation is the process of decoding an mRNA message into a protein, while transcription is when segments of DNA serve as templates to produce complementary RNA molecules.
What is the fourth step of translation?
When the ribosome reaches a stop codon, it releases both the newly formed polypeptide and the mRNA molecule, completing the process of translation
In regulating genes in prokaryotes, what is an operator (O)?
Where a DNA-binding protein known as the lac repressor can bind to DNA
What does an operator do?
Where a DNA-binding protein known as the lac repressor can bind to DNA
What is the first step of translation?
Translation begins when a ribosome attaches to an mRNA molecule in the cytoplasm
Part of one chromosome breaks off and attaches to another
Translocation
Describe a translocation chromosomal mutation.
Translocation occurs when part of one chromosome breaks off and attaches to another
What are the stop codons that end the translation?
UAA, UAG, UGA
What is the codon for tryptophan? (Use codon wheel)
UGG
Give an example of how environmental factors can affect the process of metamorphosis.
Under less than ideal conditions—a drying pond, a high density of predators, low amounts of food—tadpoles may speed up their metamorphosis
What does a repressor protein do?
When lactose is not present, the lac repressor binds to the operating (O) region, blocking the RNA polymerase from reaching the lac genes to begin transcription
How does a repressor protein turn off the lac operon?
When lactose is present, it attaches to the lac repressor and changes the shape of the repressor protein in a way that causes it to fall off the operator
What does lactose do?
When lactose is present, it attaches to the lac repressor and changes the shape of the repressor protein in a way that causes it to fall off the operator
When would a bacteria need to use the "lac" operon?
When the bacteria is in the presence of lactose
What does RNA polymerase do?
When the repressor is no longer bound to the O site, RNA polymerase can bind to the promoter and transcribe the genes of the operon
Give a description of the completing of a polypeptide.
When the ribosome reaches a stop codon, it releases both the newly formed polypeptide and the mRNA molecule, completing the process of translation
Metamorphosis is:
a series of transformations from one life stage to another
Some mutations that affect individual organisms can also affect:
a species or even an entire ecosystem
(Look at diagrams on page 2 of 13.1 RNA Worksheet) Name the RNA molecules from left to right.
a. tRNA, b. mRNA, c. rRNA
Polyploidy is the condition in which:
an organism has an extra set of chromosomes
Mutations are important to the evolution of a species because they:
are a source of genetic variability
The sequence of ___________ in mRNA complements the sequence in the DNA template.
bases
In most cases, multiple transcription factors must:
bind before RNA polymerase is able to attach to the promoter region and start transcription
Cancer is the product of a mutation that:
causes the uncontrolled growth of cells
Homeobox genes are expressed in:
certain regions of the body
Chromosomal mutations involve:
changes in the number or structure of chromosomes
The process through which cells become specialized in structure and function is:
differentiation
Some of the most harmful mutations are those that:
dramatically change protein structure or gene activity
The miRNA sticks to certain mRNA molecules and stops them:
from passing on their protein-making instructions
Small changes in genes can ______________ over time
gradually accumulate
small changes in genes:
gradually accumulate over time
If mutagens interact with DNA, they can produce mutations at:
high rates
Some of the variation produced by mutations can be:
highly advantageous to an organism or species
What is the function of mRNA?
mRNA carries copies of instructions needed for assembling amino acids into proteins
What is the function of messenger RNA (mRNA)?
mRNA carries copies of instructions needed for assembling amino acids into proteins
Use the analogy of the master plan and blueprints used by builders to identify what represents messenger RNA, where the "ribosome" is, and who performs the same kind of job as transfer RNA.
mRNA is the blueprint because it carries the instructions from the nucleus to the cytoplasm or construction site. Ribosomes are the construction site because they are where protein synthesis takes place. tRNA is like the construction workers because it transfers amino acids or necessary building materials to the ribosomes or construction site.
Give a description of the beginning of translation.
mRNA is transcribed in the nucleus and then enters the cytoplasm for translation where it attaches to a ribosome
The "switches" that trigger particular patterns of development and differentiation in cells and tissues are:
master control genes
Homoeotic genes are:
master control genes that regulate organs that develop in specific parts of the body
The resulting mutations:
may or may not affect an organism
Genetic material can be altered by:
natural events or by artificial means
Clusters of Hox genes are found in:
nearly all animals
In eukaryotes, RNA is formed in the _______________ and then travels to the _____________________.
nucleus, cytoplasm
Hox genes are arranged in:
the exact order in which they are expressed, from anterior to posterior
Chromosomal mutations can change:
the location of genes on chromosomes and can even change the number of copies of some genes
RNA interference is found:
throughout the living world and that it even plays a role in human growth and development
The process of using DNA to produce complementary RNA molecules is called _____________________.
transcription
As an embryo develops, different sets of genes are regulated by:
transcription factors and repressors
A possible mutagen is:
ultraviolet light